Nucleotide sequences of the cDNA and an intronless pseudogene for human lactate dehydrogenase-A isozyme

The Regulation and Function of Lactate Dehydrogenase A: Therapeutic Potential in Brain Tumor

There are over 120 types of brain tumor and approximately 45% of primary brain tumors are gliomas, of which glioblastoma multiforme (GBM) is the most common and aggressive with a median survival rate of 14 months. Despite progress in our knowledge, current therapies are unable to effectively combat primary brain tumors and patient survival remains poor. Tumor metabolism is important to consider in therapeutic approaches and is the focus of numerous research investigations. Lactate dehydrogenase A (LDHA) is a cytosolic enzyme, predominantly involved in anaerobic and aerobic glycolysis (the Warburg effect); however, it has multiple additional functions in non‐neoplastic and neoplastic tissues, which are not commonly known or discussed. This review summarizes what is currently known about the function of LDHA and identifies areas that would benefit from further exploration. The current knowledge of the role of LDHA in the brain and its potential as a therapeutic target for brain tumors will also be highlighted. The Warburg effect appears to be universal in tumors, including primary brain tumors, and LDHA (because of its involvement with this process) has been identified as a potential therapeutic target. Currently, there are, however, no suitable LDHA inhibitors available for tumor therapies in the clinic.

Computational analyses of mammalian lactate dehydrogenases: human, mouse, opossum and platypus LDHs

Computational methods were used to predict the amino acid sequences and gene locations for mammalian lactate dehydrogenase (LDH) genes and proteins using genome sequence databanks. Human LDHA, LDHC and LDH6A genes were located in tandem on chromosome 11, while LDH6B and LDH6C genes were on chromosomes 15 and 12, respectively. Opossum LDHC and LDH6B genes were located in tandem with the opossum LDHA gene on chromosome 5 and contained 7 (LDHA and LDHC) or 8 (LDH6B) exons. An amino acid sequence prediction for the opossum LDH6B subunit gave an extended N-terminal sequence, similar to the human and mouse LDH6B sequences, which may support the export of this enzyme into mitochondria. The platypus genome contained at least 3 LDH genes encoding LDHA, LDHB and LDH6B subunits. Phylogenetic studies and sequence analyses indicated that LDHA, LDHB and LDH6B genes are present in all mammalian genomes examined, including a monotreme species (platypus), whereas the LDHC gene may have arisen more recently in marsupial mammals.

Electrophoretic Variant of a Lactate Dehydrogenase Isoenzyme and Selective Promoter Methylation of the LDHA Gene in a Human Retinoblastoma Cell Line

Background: Lactate dehydrogenase (LD), a tetrameric product of the genes LDHA and LDHB, may be increased in sera of cancer patients. A variant isoenzyme with electrophoretic mobility between LD2 and LD3 (LD2ex) has been described in patients, but its molecular nature is largely unknown.

Methods: A newly established retinoblastoma cell line, NCC-RbC-51 (R51), showed an isoenzyme pattern with only two bands, LD1 and LD2ex. We investigated the isoenzymes by Northern blot, Western blot, and methylation analysis and PCR.

Results: Northern blot analysis revealed that R51 cells expressed no wild-type/somatic LDHA mRNA, but did express a small amount of LDHA-related mRNA with a slightly higher molecular mass. Western blot analysis confirmed the anti-LDHA-reactive protein with a 3-kDa higher molecular mass. Treatment of R51 cells with the demethylating agent 5-aza-2′-deoxycytidine restored the expression of the LD2, -3, -4, and -5 isoenzymes. PCR analysis of sodium bisulfite-treated genomic DNA revealed that the CpG island in the promoter region around exon a of the LDHA gene was completely methylated. Reverse transcription-PCR analysis and direct sequencing revealed that R51 cells expressed a RNA with the sequence of the human homolog of a murine testis-specific variant that has exon 0 as the 5′ noncoding sequence. LDHB was expressed normally in R51 cells.

Conclusions: The somatic LDHA in R51 cells is transcriptionally silenced by promoter hypermethylation around exon a, leaving only LDHB to be expressed normally and a testis-specific variant transcript of LDHA containing exon 0. LD2ex possibly results from tetramerization of three wild-type LDHB molecules and one variant LDHA product.

Lactate dehydrogenase production and release in a newly established human myeloma cell line

Aggressive multiple myeloma with high serum lactate dehydrogenase (LDH) often has unusual clinical features and is considered to be a distinct clinical entity of multiple myeloma. A myeloma cell line, designated Maska-98, was established from the bone marrow of a patient with aggressive myeloma with extremely high serum LDH that was resistant to conventional chemotherapy. Maska-98 cells had morphological features of immature plasma cells, and immunophenotypic analysis showed that the cells expressed the plasma cell-associated surface antigens including CD38, 49d, and 56, but no T- or B-cell antigens, such as CD2, 3, 4, 8, 19, and 20. Maska-98 cells contained cytoplasmic immunoglobulin (IgG lambda). By utilizing this cell line we demonstrated that the myeloma cells produce and release a large amount of LDH, since (i) abundant LDH was found in the culture supernatant of Maska-98, (ii) immunocytochemical analysis showed that cytoplasm of the cells was strongly stained with anti-LDH monoclonal antibody, and (iii) Maska-98 cells expressed a greater amount of LDH mRNA than the T-cell line TALL-1, as shown by reverse transcription-polymerase chain reaction. As far as we know, there is no report of a myeloma cell line producing excess LDH. Therefore, Maska-98 would provide a novel source for further studies of the pathogenesis of aggressive multiple myeloma with high serum LDH.

IMP-L3, A 20-hydroxyecdysone-responsive gene encodes Drosophila lactate dehydrogenase: structural characterization and developmental studies

IMP-L3, a gene isolated as a potential mediator of imaginal disc morphogenesis in Drosophila melanogaster, encodes lactate dehydrogenase (LDH). The predicted amino acid sequence of IMP-L3 is 58-61% identical to those of human LDHs. In cultured imaginal discs, IMP-L3 transcript levels and LDH enzyme activity increase in response to the steroid hormone, 20-hydroxyecdysone. In embryos, IMP-L3 transcript and LDH activity appear in developing somatic muscles by late stage 13, well before the onset of muscular contraction. High levels of transcript and LDH activity persist throughout embryogenesis and throughout larval development. The gene has been localized by in situ hybridization and deficiency mapping to 65A7-65B2 on the third chromosome. LDH activity is reduced to approximately 50% of wild type in animals heterozygous for a deficiency that removes the 65A-B region. Embryos deficient for the 65A-b region lack LDH activity. We conclude that IMP-L3 is the only gene that encodes LDH in Drosophila.

Isolation and expression of lactate dehydrogenase genes from Rhizopus oryzae

Rhizopus oryzae is used for industrial production of lactic acid, yet little is known about the genetics of this fungus. In this study I cloned two genes, ldhA and ldhB, which code for NAD(+)-dependent L-lactate dehydrogenases (LDH) (EC 1.1.1.27), from a lactic acid-producing strain of R. oryzae. These genes are similar to each other and exhibit more than 90% nucleotide sequence identity and they contain no introns. This is the first description of ldh genes in a fungus, and sequence comparisons revealed that these genes are distinct from previously isolated prokaryotic and eukaryotic ldh genes. Protein sequencing of the LDH isolated from R. oryzae during lactic acid production confirmed that ldhA codes for a 36-kDa protein that converts pyruvate to lactate. Production of LdhA was greatest when glucose was the carbon source, followed by xylose and trehalose; all of these sugars could be fermented to lactic acid. Transcripts from ldhB were not detected when R. oryzae was grown on any of these sugars but were present when R. oryzae was grown on glycerol, ethanol, and lactate. I hypothesize that ldhB encodes a second NAD(+)-dependent LDH that is capable of converting L-lactate to pyruvate and is produced by cultures grown on these nonfermentable substrates. Both ldhA and ldhB restored fermentative growth to Escherichia coli (ldhA pfl) mutants so that they grew anaerobically and produced lactic acid.

Red blood cell enzymes and their clinical application

Red blood cell enzyme activities are measured mainly to diagnose hereditary nonspherocytic hemolytic anemia associated with enzyme anomalies. At least 15 enzyme anomalies associated with hereditary hemolytic anemia have been reported. Some nonhematologic disease can also be diagnosed by the measurement of red blood cell enzyme activities in the case in which enzymes of red blood cells and the other organs are under the same genetic control. Progress in molecular biology has provided a new perspective. Techniques such as the polymerase chain reaction and single-strand conformation polymorphism analysis have greatly facilitated the molecular analysis of erythroenzymopathies. These studies have clarified the correlation between the functional and structural abnormalities of the variant enzymes. In general, the mutations that induce an alteration of substrate binding site and/or enzyme instability might result in markedly altered enzyme properties and severe clinical symptoms.

Study of Burkitt lymphoma cell line proteins by high resolution two-dimensional gel electrophoresis and nanoelectrospray mass spectrometry

We paper describe a mass spectrometric approach generally applicable for the rapid identification and characterization of proteins isolated by two-dimensional gel electrophoresis (2-DE). The highly sensitive nanoflow-electrospray mass spectrometry employing a quadrupole-time of flight mass spectrometer was used for the direct identification of proteins from the peptide mixture generated from only one high resolution 2-DE gel without high performance liquid chromatography (HPLC) separation or Edman sequencing. Due to the high sensitivity and high mass accuracy of the instrument employed, this technique proved to be a powerful tool for the identification of proteins from femtomole amounts of materials. We applied the technique for the investigation of Burkitt lymphoma BL60 cell proteins. This cell line has been used as a model to assign apoptosis-associated proteins by subtractive analysis of normal and apoptotic cells. From the nuclear fraction of these cells, 36 protein spots were examined, from only one micropreparative Coomassie Brilliant Blue R-250 stained gel, after proteolytic digestion by matrix assisted laser desorption ionization (MALDI) and nanospray mass spectrometry (MS). In combination with database searches, of 33 proteins were successfully identified by nanospray-MS/MS-sequencing of up to eight peptides per protein. Three proteins were new proteins not listed in any of the available databases. Some of the identified proteins are known to be involved in apoptosis processes, the others were common proteins in the eukaryotic cell. The given technique and the protein data are the basis for construction of a database to compare normal and apoptosis-induced cells and, further, to enable fast screening of drug impact in apoptosis-associated processes.

Quantification of relative expression of genes with homologous sequences using fluorescence-based single-strand conformation polymorphism analysis--application to lactate dehydrogenase and cyclooxygenase isozymes

The combination of reverse transcribed-PCR and fluorescence-based single strand conformation polymorphism analysis has been proposed for the quantitative determination of ratio of mRNA molecules with homologous sequences. We applied this procedure to lactate dehydrogenase subunits M and H, and cyclooxygenase 1 and 2. We designed fluorescence labeled common PCR primers in the sequences highly homologous between two subunit and isozyme cDNAs, and performed reverse transcribed-PCR and fluorescence-based single strand conformation polymorphism analysis. PCR efficiency was almost the same for the different target sequences, so analysis of mixtures of known amounts of lactate dehydrogenase M and H revealed linear and precise proportions of lactate dehydrogenase M mRNA. It was shown that template concentrations and number of PCR cycles did not affect the determination of proportions of lactate dehydrogenase M to total lactate dehydrogenase. The procedure was applicable to a determination of cyclooxygenase-2 proportion; furthermore, the present procedure could be easily applied to investigation of expression levels of genes encoding mRNAs with homologous sequences.

Substrate and cofactor specificity and selective inhibition of lactate dehydrogenase from the malarial parasite P. falciparum

Lactate dehydrogenase from the malarial parasite Plasmodium falciparum has many amino acid residues that are unique compared to any other known lactate dehydrogenase. This includes residues that define the substrate and cofactor binding sites. Nevertheless, parasite lactate dehydrogenase exhibits high specificity for pyruvic acid, even more restricted than the specificity of human lactate dehydrogenases M4 and H4. Parasite lactate dehydrogenase exhibits high catalytic efficiency in the reduction of pyruvate, kcat/Km = 9.0 x 10(8) min(-1) M(-1). Parasite lactate dehydrogenase also exhibits similar cofactor specificity to the human isoforms in the oxidation of L-lactate with NAD+ and with a series of NAD+ analogs, suggesting a similar cofactor binding environment in spite of the numerous amino acid differences. Parasite lactate dehydrogenase exhibits an enhanced kcat with the analog 3-acetylpyridine adenine dinucleotide (APAD+) whereas the human isoforms exhibit a lower kcat. This differential response to APAD+ provides the kinetic basis for the enzyme-based detection of malarial parasites. A series of inhibitors structurally related to the natural product gossypol were shown to be competitive inhibitors of the binding of NADH. Slight changes in structure produced marked changes in selectivity of inhibition of lactate dehydrogenase. 7-p-Trifluoromethylbenzyl-8-deoxyhemigossylic acid inhibited parasite lactate dehydrogenase, Ki = 0.2 microM, which was 65- and 400-fold tighter binding compared to the M4 and H4 isoforms of human lactate dehydrogenase. The results suggest that the cofactor site of parasite lactate dehydrogenase may be a potential target for structure-based drug design.

Removal of substrate inhibition in a lactate dehydrogenase from human muscle by a single residue change

High concentrations of ketoacid substrates inhibit most natural hydroxyacid dehydrogenases due to the formation of an abortive enzyme-NAD+-ketoacid complex. It was postulated that this substrate inhibition could be eliminated from lactate dehydrogenases if the rate of NAD+ dissociation could be increased. An analysis of the crystal structure of mammalian LDHs showed that the amide of the nicotinamide cofactor formed a water-bridged hydrogen bond to S163. The LDH of Plasmodium falciparum is not inhibited by its substrate and, uniquely, in this enzyme the serine is replaced by a leucine. In the S163L mutant of human LDH-M4 pyruvate inhibition is, indeed, abolished and the enzyme retains high activity. However, the major contribution to this effect comes from a weakening of the interaction of pyruvate with the enzyme-coenzyme complex.

Molecular genetic studies of muscle lactate dehydrogenase deficiency in white patients

We identified two new mutations in 2 white patients with muscle lactate dehydrogenase deficiency. Both patients had exercise intolerance, cramps, and recurrent myoglobinuria. One patient was homozygous for a 2-bp deletion in exon 5, resulting in a frameshift with premature termination of translation. The second patient was homozygous for a G-->A substitution at the 3' end of exon 2, leading to exon skipping and splicing of exon 1 to exon 3; the aberrantly spliced messenger RNA contains a frameshift, resulting in premature termination of translation. The present report provides evidence of molecular genetic heterogeneity in white patients with muscle lactate dehydrogenase deficiency.

Evolutionary relationships of lactate dehydrogenases (LDHs) from mammals, birds, an amphibian, fish, barley, and bacteria: LDH cDNA sequences from Xenopus, pig, and rat

The nucleotide sequences of the cDNAs encoding LDH (EC 1.1.1.27) subunits LDH-A (muscle), LDH-B (liver), and LDH-C (oocyte) from Xenopus laevis, LDH-A (muscle) and LDH-B (heart) from pig, and LDH-B (heart) and LDH-C (testis) from rat were determined. These seven newly deduced amino acid sequences and 22 other published LDH sequences, and three unpublished fish LDH-A sequences kindly provided by G. N. Somero and D. A. Powers, were used to construct the most parsimonious phylogenetic tree of these 32 LDH subunits from mammals, birds, an amphibian, fish, barley, and bacteria. There have been at least six LDH gene duplications among the vertebrates. The Xenopus LDH-A, LDH-B, and LDH-C subunits are most closely related to each other and then are more closely related to vertebrate LDH-B than LDH-A. Three fish LDH-As, as well as a single LDH of lamprey, also seem to be more related to vertebrate LDH-B than to land vertebrate LDH-A. The mammalian LDH-C (testis) subunit appears to have diverged very early, prior to the divergence of vertebrate LDH-A and LDH-B subunits, as reported previously.

Expression of mitochondrial genes and DNA-repair-related nuclear genes is altered in xeroderma pigmentosum fibroblasts

Differential hybridization was used to detect repair defects in xeroderma pigmentosum (XP) that are not amenable to current analyses. cDNA libraries were constructed from cytoplasmic RNA of normal and XP fibroblast strains (complementation groups A and D) and analyzed for differential gene expression. More than 40,000 lambda gt10 cDNA clones were differentially screened with in vitro transcripts made from cDNA in the pBluescript vector. Six differential clones were detected in the libraries of the XP group A and D strains which caused stronger or weaker signals when probed with transcripts from XP strains than with those from the normal strains. Two clones coded for mitochondrial genes: mitochondrial 16 S rRNA and ATPase 6L. Overexpression of mitochondrial genes in XP may indicate that functions of the ATP-generating system are impaired since such functions are intensified whenever they become insufficient, for example as a consequence of DNA damage. It is tempting to assume that abnormal mitochondria are one of the causes for the neurological malfunctions in XP. Furthermore, densitometric analysis of Northern blots revealed that mRNA of lactate dehydrogenase, chain M, was less abundant in four XP group A strains (extent of reduction: 70%) and in two XP group D strains (extent of reduction: 58%). Enzyme activity was also diminished. In addition, mRNA of the gene for glyceraldehyde-3-phosphate dehydrogenase was less expressed in the same XP group A and D fibroblast strains investigated (reduction in both complementation groups: 50%). Both glycolytic enzymes have nuclear functions apart from their role in sugar metabolism. Lactate dehydrogenase, chain M, is identical to a helix-destabilizing protein; it is closely associated with chromatin and unfolded DNA, suggesting a role in DNA synthesis and transcription. The 37-kDa subunit of glyceraldehyde-3-phosphate dehydrogenase is involved in transcription and was shown to be identical to uracil-DNA glycosylase, a base-excision repair enzyme. We presume that the nuclear functions of these glycolytic enzymes may be thwarted in the XP strains investigated and may account for malfunctions in XP, particularly for neurological disturbances.

An examination of the generation-time effect on molecular evolution

By using DNA sequences of 17 mammalian genes, the generation-time effect is estimated separately for synonymous substitutions and nonsynonymous substitutions. Star phylogenies composed of rodentia, artiodactyla, and primates are examined. The generation-time effect is found to be more conspicuous for synonymous substitutions than for non-synonymous substitutions, by using the methods of (i) Nei and Gojobori, (ii) Li, and (iii) Ina. The proportion of accepted amino acid substitutions in evolution is estimated to be about twice as large in the primate lineage as in the rodent lineage. This result is in accord with the nearly neutral theory of molecular evolution.

Recognition and separation of isoenzymes by metal chelates. Immobilized metal ion affinity partitioning of lactate dehydrogenase isoenzymes

Poly(ethylene glycol) (PEG)-bound chelated metal ions partition preferentially into the top, PEG-rich, phase of a PEG-salt or PEG-dextran aqueous two-phase system. Extraction by this soluble affinity ligand of proteins is due to a selective interaction of the chelated metal ion with accessible histidine residues on the protein surface. Using Cu-iminodiacetate-PEG (Cu-IDA-PEG) the surface of lactate dehydrogenase (LDH) isoenzymes from different species was probed for the presence of metal chelate binding sites. It was demonstrated that the homotetramers (LDH-1)(H4) from rabbit, bovine and pig displayed weak binding to chelated copper whereas the M4-type isoenzymes (LDH-5) bound strongly to this ligand. The binding of the different heterotetramers increases as the number of M-type subunits increases. In contrast, the human isoenzymes are bound to chelated copper in a reversed sequence. The comparison of the affinity partitioning effect of Cu-IDA-PEG in PEG-salt and PEG-dextran systems revealed that the discriminatory effect of copper is promoted by high salt concentrations. Resolution of isoenzymes by multiple extraction using counter-current distribution provides valuable data on the partitioning of enzymes relative to that of the bulk proteins. The efficacy of metal chelate affinity partitioning for the purification of LDH from tissue samples by batchwise extraction was also demonstrated.

Expression of Plasmodium falciparum lactate dehydrogenase in Escherichia coli

A Plasmodium falciparum gene is described which encodes lactate dehydrogenase activity (P. falciparum LDH). The P. falciparum LDH gene contains no introns and is present in a single copy on chromosome 13. P. falciparum LDH was expressed in all asexual blood stages as a 1.6-kb mRNA. The predicted 316 amino acid protein coding region of P. falciparum LDH was inserted into the prokaryotic expression vector pKK223-3 and a 33-kDa protein having LDH activity was synthesized in Escherichia coli. P. falciparum LDH primary structure displays high amino acid similarity (50-57%) to vertebrate and bacterial LDH, but lacks the amino terminal extension observed in all vertebrate LDH. The majority of amino acid residues implicated in substrate and coenzyme binding and catalysis of other LDH are well conserved in P. falciparum LDH. However, several notable differences in amino acid composition were observed. P. falciparum LDH contained several distinctive single amino acid insertions and deletions compared to other LDH enzymes, and most remarkably, it contained a novel insertion of 5 amino acids within the conserved mobile loop region near arginine residue 109, a residue which is known to make contact with pyruvate in the ternary complex of other LDH. These results suggest that novel features of P. falciparum LDH primary structure may be correlated with previously characterized and distinctive kinetic, biochemical, immunochemical, and electrophoretic properties of P. falciparum LDH.

Sequence analysis of teleost retina-specific lactate dehydrogenase C: evolutionary implications for the vertebrate lactate dehydrogenase gene family

At least two gene duplication events have led to the three lactate dehydrogenase (LDH; EC 1.1.1.27) isozymes (LDH-A, LDH-B, and LDH-C) of chordates. The prevailing model for the evolution of the LDH loci involves duplication of a primordial LDH locus near the origin of vertebrates, giving rise to Ldh-A and Ldh-B. A third locus, designated Ldh-C, is expressed in the spermatocytes of mammals and a single family of birds and in the eye or liver tissues of teleost fishes. Ldh-C might have arisen independently in these taxa as duplications of either Ldh-A or Ldh-B. Several authors have challenged this traditional hypothesis on the basis of amino acid sequence and immunological similarity of the three LDH isozymes. They suggest that the primordial LDH gene was duplicated to form Ldh-C and a locus that later gave rise to Ldh-A and Ldh-B. We have differentiated between these hypotheses by determining the cDNA sequence of the retina-specific LDH-C from a teleost, Fundulus heteroclitus. On the basis of amino acid sequence similarity, we conclude that the LDH-C isozymes in fish and mammals are not orthologous but derive from independent gene duplications. Furthermore, our phylogenetic analyses support previous hypotheses that teleost Ldh-C is derived from a duplication of the Ldh-B locus.

Cloning and sequence analysis of the gene encoding L-lactate dehydrogenase from Lactococcus lactis: evolutionary relationships between 21 different LDH enzymes

Lactate dehydrogenase (LDH; EC1.1.1.27) is a key enzyme in the fermentation of milk by lactic acid bacteria used in the dairy industry. An 800-bp DNA fragment containing part of the gene (ldh) encoding LDH was amplified from Lactococcus lactis in a polymerase chain reaction using primers designed from the partial amino acid sequence of a lactococcal LDH. This fragment was radioactively labelled and used to probe a phage lambda library of Lc. lactis genomic DNA. Fragments containing ldh were subcloned from lambda to pUC13 and pUC18 and a 1.2-kb region was sequenced. The deduced aa sequence reveals that the lactococcal LDH is highly homologous to the LDHs of other organisms. The active site and several other domains of unknown function are highly conserved between all LDH enzymes (prokaryotic and eukaryotic). An evolutionary study of LDH sequences clearly divides the prokaryotic from the eukaryotic enzymes except for the Bifidobacterium longum LDH which anomalously groups with the eukaryotic enzymes. The LDHs from Gram-positive bacteria form a separate group from the enzymes from the Gram-negative organisms. The lactococcal LDH is phylogenetically closest to the streptococcal LDH.

Regulation of the expression of lactate dehydrogenase isozymes in human lymphocytes

Mitogen activation of human peripheral lymphocytes leads to a switch in the isozymes of LDH; resting cells contain low activities of only the B4 and B3A forms, whereas activated cells contain high activities of the A4 and A3B forms. B4 LDH is not altered in activated cells. In this study we show that the appearance of the A subunits occurs concomitantly with a several fold increase in the steady state levels of LDH-A mRNA. Responses in LDH-A mRNA are observed within 12 hrs of activation, and are, thus, associated with the G0/G1 transition or with early G1 (Marjanovic et al. Exp. Cell Res. (1991) 193: 425-431). Maximal expression of LDH-A mRNA requires both phorbol ester and concanavalin A, implying a complex regulatory pathway involving cascade systems activated through both the antigen receptor (TR) and protein kinase C.

Human centrosomal epitope is shared specifically with human lactate dehydrogenase-B isozyme

A rabbit serum (0013) used to identify pericentriolar proteins from isolated centrosomes (Gosti-Testu, F., Marty, M.C., Berges, J., Maunoury, R. and Bornens, M. (1986) EMBO J. 5, 2545-2550) was shown also to react through the same epitope with several non-centrosomal proteins including a major 36 kDa cytosolic antigen. This protein was identified to be human lactate dehydrogenase and the co-distribution of 0013 epitope on the centrosomal protein and on lactate dehydrogenase (LDH) was shown to be specific for human cells (Gosti, F., Marty, M.C., Courvalin, J.C., Maunoury, R. and Bornens, M. (1987) Proc. Natl. Acad. Sci. USA 84, 1000-1004). Human hepatic cells constitute, so far, the only exception to this co-distribution rule. By using this cell type which expresses only the LDH-A4 isozyme, we demonstrate that 0013 epitope is specific for the human LDH-B subunit, making serum 0013 the strongest anti-LDH-B available so far. The evolutionary and physiological significance of this situation is discussed.

Evolutionary implications of the cDNA sequence of the single lactate dehydrogenase of a lamprey

All vertebrates other than lampreys exhibit multiple loci encoding lactate dehydrogenase +ADL-LDH; (S)-lactate:NAD+ oxidoreductase, EC 1.1.1.27+BD. Of these loci, Ldh-A is expressed predominantly in muscle, Ldh-B is expressed predominantly in heart, and Ldh-C (where present) exhibits different tissue-restricted patterns of expression depending on the taxon. To examine the relationship of the single LDH of lampreys to other vertebrate LDHs, we have determined the cDNA sequence of the LDH of the sea lamprey Petromyzon marinus and compared it to previously published sequences from bacteria, plants, and vertebrates. The lamprey sequence exhibits a mixture of features of both LDH-A and LDH-B at the amino acid level that may account for its intermediate kinetic properties. Both distance and maximum parsimony analyses strongly reject a relationship of lamprey LDH with mammalian LDH-C but do not significantly distinguish among remaining alternative phylogenetic hypotheses. Evolutionary parsimony analyses suggest that the lamprey LDH is related to Ldh-A and that the single locus condition has arisen as a result of the loss of Ldh-B (prior to the appearance of Ldh-C). The collection of LDH sequences for further studies of the evolution of the vertebrate LDH gene family will be facilitated by the PCR approach that we have used to obtain the lamprey sequence.

Analysis of protein loop closure. Two types of hinges produce one motion in lactate dehydrogenase

As shown in previous crystallographic investigations, upon binding lactate and NAD, lactate dehydrogenase undergoes a large conformational change that results in a surface loop moving roughly 10 A to cover the active site. In addition, there are appreciable movements (approximately 2 A) of five helices and three other loops. We demonstrate by a new fitting procedure that the loop moves on two hinges separated by a relatively rigid type II turn. The first hinge has few steric constraints on it, and its motion can be well accounted for by large changes in two torsion angles, i.e. as in a classic hinge motion. In contrast, the second hinge, which is part of a helix connected to the end of the loop, has many more constraints on it and distributes its deformation over more torsion angles. This novel motion involves the helix stretching and splitting into alpha-helical and 3(10)-helical components and substantial side-chain repacking in the sense of "cogs hopping between grooves" at its interface with the end of a neighboring helix. The loop is stabilized by five transverse (across loop) hydrogen bonds. These are preserved, through the conformational change and through 17 lactate dehydrogenase sequences, more than the longitudinal hydrogen bonds down the sides of the loop. Through a network of contacts, many of them conserved hydrophobic residues, the motion of the loop is propagated outward to structures that have no direct contact with the ligands. These moving structures are on the surface of the protein, and the whole protein can be subdivided into concentric shells of increasing mobility.

Molecular cloning and characterization of a novel glycoprotein, gp34, that is specifically induced by the human T-cell leukemia virus type I transactivator p40tax

We have cloned and sequenced a cDNA encoding gp34, a novel glycoprotein expressed in cells bearing human T-cell leukemia virus type I (HTLV-I). HTLV-I has a trans-acting transcriptional activator, p40tax, that is thought to be implicated in leukemogenesis through the activation of cellular enhancers. With a subline (JPX-9) of the human T-cell line Jurkat, in which p40tax is inducible, gp34 was shown to be of cellular origin and to be transcriptionally activated by p40tax. It was also demonstrated that two species of mRNA are generated from one copy of the gp34 gene and that these mRNAs encode the identical gp34 product and differ in the 3' untranslated region. Analysis of the deduced amino acid sequence of gp34 showed that it lacks typical signal peptides; however, it has a hydrophobic stretch for membrane anchoring and four possible N-linked glycosylation sites at the carboxy-terminal portion, indicating that it belongs to the family of membrane proteins whose carboxy-terminal portion protrudes out of the cell. The gp34 gene displayed relatively delayed induction compared with other genes activated by p40tax. Taken together with the observation of the dependence of gp34 expression on HTLV-I p40tax, unlike other p40tax-dependent genes such as those for the interleukin-2 receptor alpha chain and c-fos, which are expressed or induced under physiological conditions, we predict that the mechanism involved in the induction of gp34 expression by p40tax is distinct from and more intricate than those for the previously characterized genes.

Molecular cloning and characterization of a novel glycoprotein, gp34, that is specifically induced by the human T-cell leukemia virus type I transactivator p40tax

We have cloned and sequenced a cDNA encoding gp34, a novel glycoprotein expressed in cells bearing human T-cell leukemia virus type I (HTLV-I). HTLV-I has a trans-acting transcriptional activator, p40tax, that is thought to be implicated in leukemogenesis through the activation of cellular enhancers. With a subline (JPX-9) of the human T-cell line Jurkat, in which p40tax is inducible, gp34 was shown to be of cellular origin and to be transcriptionally activated by p40tax. It was also demonstrated that two species of mRNA are generated from one copy of the gp34 gene and that these mRNAs encode the identical gp34 product and differ in the 3' untranslated region. Analysis of the deduced amino acid sequence of gp34 showed that it lacks typical signal peptides; however, it has a hydrophobic stretch for membrane anchoring and four possible N-linked glycosylation sites at the carboxy-terminal portion, indicating that it belongs to the family of membrane proteins whose carboxy-terminal portion protrudes out of the cell. The gp34 gene displayed relatively delayed induction compared with other genes activated by p40tax. Taken together with the observation of the dependence of gp34 expression on HTLV-I p40tax, unlike other p40tax-dependent genes such as those for the interleukin-2 receptor alpha chain and c-fos, which are expressed or induced under physiological conditions, we predict that the mechanism involved in the induction of gp34 expression by p40tax is distinct from and more intricate than those for the previously characterized genes.

Comprehensive two-dimensional gel protein databases offer a global approach to the analysis of human cells: the transformed amnion cells (AMA) master database and its link to genome DNA sequence data

A total of 3430 polypeptides (2592 cellular; 838 secreted) from transformed human amnion cells (AMA) labeled with [35S]methionine were separated and recorded using computer-aided two-dimensional (2-D) gel electrophoresis. A master 2-D gel database of cellular protein information that includes both qualitative and quantitative annotations has been established. The protein numbers in this database differ from those reported in an earlier version (Celis et al. Leukemia 1988, 2,561-602) as a result of changes in the scanning hardware. The reported information includes: percentage of total radioactivity recovered from the gels (based on quantitations of polypeptides labeled with a mixture of 16 14C-amino acids), protein name (including credit to investigators that aided identification), antibody against protein, cellular localization, (nuclear, 40S hnRNP, 20S snRNP U5, proteasomes, endoplasmic reticulum, mitochondria, Golgi, ribosomes, intermediate filaments, microfilaments and microtubules), levels in fetal human tissues, partial protein sequences (containing information on 48 human proteins microsequenced so far), cell cycle-regulated proteins, proteins sensitive to interferons alpha, beta, and gamma, heat shock proteins, annexins and phosphorylated proteins. The results presented should be considered as the initial phase of a joint effort between our laboratories to undertake a general and systematic analysis of human proteins. Using this integrated approach it will be possible to identify phenotype-specific proteins, to microsequence them and store the information in the database, to identify the corresponding genes, to search for homology with previously characterized proteins and to study the function of groups of proteins (pathways, organelles, etc.) that exhibit interesting regulatory properties. In particular, the 2-D gel protein database may become increasingly important in view of the concerted effort to map and sequence the entire human genome.

Expression of the copy DNA for human A4 and B4 L-lactate dehydrogenases in Escherichia coli

The human LDH-A and LDH-B cDNAs, containing the coding regions for the L-lactate dehydrogenase A4 (M) and B4 (H) polypeptides respectively have been cloned into Escherichia coli to place the cDNAs under the control of hybrid E. coli/Bacillus stearothermophilus transcriptional and translational signals. Human A4- and B4-isoenzymes are produced in E. coli cells harbouring the expression plasmids pHLDHA22 and pHLDHB10 at levels of 6.5 and 1.5% of the soluble protein of the cell, respectively. The tac promoter of these vectors was not induced by isopropyl beta-D-thiogalactopyranoside. The A4 and B4 human isoenzymes synthesized in E. coli were purified to homogeneity and show the same properties as isoenzymes isolated from human tissue. The amino acid sequences of 12 N-terminal residues of the human isoenzymes synthesized in E. coli were determined to be identical to those deduced from the DNA sequence of the cloned cDNAs except that the N-terminal methionine was absent from both. However, in contrast to LDH made in human cells, acetylation of the N-terminal alanine does not take place in E. coli cells.

Human lactate dehydrogenase-B processed pseudogene: nucleotide sequence analysis and assignment to the X-chromosome

Two human genomic clones containing the lactate dehydrogenase-B processed pseudogene were isolated from two patients deficient in lactate dehydrogenase-B isozyme. The sequences of 3,287 nucleotides, including the pseudogenes and its flanking regions, from both clones were found to be identical except for three differences in the pseudogenes. The sequences of 1,286 nucleotides from these two pseudogenes exhibited 93% homology with the cDNA sequence of the lactate dehydrogenase-B functional gene, and the pseudogene contained 75/76 base substitutions, 11/12 single-base deletions, and 5 single-base insertions. This pseudogene was mapped to the x-chromosome by dot-blot analysis using a probe for the pseudogene or its 5' flanking sequence.

Recent progress in the molecular genetic analysis of erythroenzymopathy

During the relatively recent period in which normal genes for most red cell enzymes have been isolated, the techniques of molecular biology have been applied to the studies of erythroenzymopathy. Single nucleotide substitutions have been identified in aldolase, triosephosphate isomerase, glucose 6-phosphate dehydrogenase, and adenylate kinase variants by the cloning and nucleotide sequence of the patients' genes. Up to now, all of the enzyme-deficient variants which have been investigated have been caused by point mutations. An exception is a hemolytic anemia secondary to increased adenosine deaminase (ADA) activity. Red cell ADA activity increases on the order of a hundred-fold in affected individuals. The basic abnormality appears to result from overproduction of structurally normal enzyme due to abnormal transcriptional or translational efficiency.

Two-dimensional gel electrophoresis, protein electroblotting and microsequencing: a direct link between proteins and genes

We have used two-dimensional gel electrophoresis as a general "preparative" method to purify proteins for microsequencing analysis. In the first experiments, proteins derived from a total extract of Nicotiana tabacum leaf tissue were directly blotted from the gel onto poly(4-vinyl-N-methylpyridinium iodide)-coated glass fiber sheets. The major spots were excised and subjected to NH2-terminal sequence analysis, which made it possible to identify five of the eight selected proteins, while two more were recognized by generated internal sequences. In a second set of experiments, proteins of human origin were separated on multiple two-dimensional gels and the Coomassie Brilliant Blue-stained spots were excised from the gels. The combined spots were re-eluted and concentrated in a new gel and blotted on Immobilon. They were fragmented by in situ proteolysis and the generated peptides were separated by reverse phase-high performance liquid chromatography and sequenced. At the average, the internal sequences that were obtained covered 35 residues per protein and allowed unambiguous identification of 13 of the 23 proteins analyzed so far. The sequence information obtained of the unidentified proteins is sufficient for further cloning. These results demonstrate that systematic sequence analysis of the major proteins seen in two-dimensional gels is within the reach of current technologies. This offers a unique opportunity to link information contained in protein databases with known or forthcoming DNA sequence data.

The cDNA and protein sequences of mouse lactate dehydrogenase B. Molecular evolution of vertebrate lactate dehydrogenase genes A (muscle), B (heart) and C (testis)

Mouse lactate dehydrogenase-B cDNAs were isolated from cDNA libraries of macrophage (ICR strain) and thymus (F1 hybrid of C57BL/6 and CBA strains), and their nucleotide sequences determined. The lactate dehydrogenase-B cDNA insert of thymus clone mB188 consists of the protein-coding sequence (1002 nucleotides), the 5' (46 nucleotides) and 3' (190 nucleotides) non-coding regions, and poly(A) tail (19 nucleotides), while macrophage clone mB168 contains a partial lactate dehydrogenase cDNA insert from codon no. 55 to the poly(A) tail. Seven silent nucleotide substitutions at codon no. 142, 143, 186, 187, 241, 285 and 292, as well as a single nucleotide change in the 3' non-coding region, were found between these different strains of mice. The predicted sequence of 333 amino acids, excluding initiation methionine, was confirmed by sequencing and/or compositional analyses of a total of 103 (31%) amino acids from tryptic peptides of mouse lactate dehydrogenase-B protein. The nucleotide sequence of the mouse coding region for lactate dehydrogenase B shows 86% identity with that of the human isoenzyme, and only eight of the 139 nucleotide differences resulted in amino acid substitutions at residues 10, 13, 14, 17, 52, 132, 236 and 317. The rates of nucleotide substitutions at synonymous and nonsynonymous sites in the mammalian lactate dehydrogenase genes are calculated. The rates of synonymous substitutions for lactate dehydrogenase genes A (muscle) and B (heart) are considerably higher than the average rate computed from human and rodent genes. The rates of nonsynonymous substitutions for lactate dehydrogenase genes A (muscle) and B (heart), particularly the latter, are highly conservative. The rates of synonymous and nonsynonymous substitutions for the lactate dehydrogenase-C gene are about the same as the average rates for mammalian genes. A phylogenetic tree of vertebrate lactate dehydrogenase protein sequences is constructed. In agreement with the previous results, this analysis further indicates that lactate dehydrogenase-C gene branched off earlier than did lactate dehydrogenase-A and lactate dehydrogenase-B genes.

A missense mutation found in human lactate dehydrogenase-B (H) variant gene

A human lactate dehydrogenase-B mutant gene was isolated from a genomic DNA library constructed from a patient with unstable LDH-B (heart) subunit. The nucleotide sequences of seven protein-coding exons were determined and a single nucleotide substitution of G by A at Arg codon CGC in exon 4 was found. This mutation results in an amino-acid replacement of a conserved arginine by histidine at the residue "173," which is involved in an anion-binding site at the P-axis of LDH subunits.

Molecular characterization of genetic mutation in human lactate dehydrogenase-A (M) deficiency

Human lactate dehydrogenase-A mutant gene was isolated from the genomic DNA library of a patient deficient in LDH-A (Muscle) subunit. The nucleotide sequences of seven protein-coding exons were determined and a deletion of 20 base-pairs in exon 6 was found. This mutation results in a frame-shift translation and premature termination. The predicted incomplete LDH-A (M) subunit containing only 259 instead of 331 amino acids appears to be degraded rapidly, since no protein was detected immunologically (Maekawa et al., Am J Hum Genet 39:232-238, 1986). In addition, three synonymous (silent) substitutions, A to C, T to C, and G to A, were observed at codons 115, 160 and 172, respectively, in this LDH-A mutant gene.

Properties and primary structure of the L-malate dehydrogenase from the extremely thermophilic archaebacterium Methanothermus fervidus

L-Malate dehydrogenase from the extremely thermophilic mathanogen Methanothermus fervidus was isolated and its phenotypic properties were characterized. The primary structure of the protein was deducted from the coding gene. The enzyme is a homomeric dimer with a molecular mass of 70 kDa, possesses low specificity for NAD+ or NADP+ and catalyzes preferentially the reduction of oxalacetate. The temperature dependence of the activity as depicted in the Arrhenius and van't Hoff plots shows discontinuities near 52 degrees C, as was found for glyceraldehyde-3-phosphate dehydrogenase from the same organism. With respect to the primary structure, the archaebacterial L-malate dehydrogenase deviates strikingly from the eubacterial and eukaryotic enzymes. The sequence similarity is even lower than that between the L-malate dehydrogenases and L-lactate dehydrogenases of eubacteria and eukaryotes. The phylogenetic meaning of this relationship is discussed.

Deletions in processed pseudogenes accumulate faster in rodents than in humans

The relative rates of point nucleotide substitution and accumulation of gap events (deletions and insertions) were calculated for 22 human and 30 rodent processed pseudogenes. Deletion events not only outnumbered insertions (the ratio being 7:1 and 3:1 for human and rodent pseudogenes, respectively), but also the total length of deletions was greater than that of insertions. Compared with their functional homologs, human processed pseudogenes were found to be shorter by about 1.2%, and rodent pseudogenes by about 2.3%. DNA loss from processed pseudogenes through deletion is estimated to be at least seven times faster in rodents than in humans. In comparison with the rate of point substitutions, the abridgment of pseudogenes during evolutionary times is a slow process that probably does not retard the rate of growth of the genome due to the proliferation of processed pseudogenes.

Nucleic acid composition, codon usage, and the rate of synonymous substitution in protein-coding genes

Based on the rates of synonymous substitution in 42 protein-coding gene pairs from rat and human, a correlation is shown to exist between the frequency of the nucleotides in all positions of the codon and the synonymous substitution rate. The correlation coefficients were positive for A and T and negative for C and G. This means that AT-rich genes accumulate more synonymous substitutions than GC-rich genes. Biased patterns of mutation could not account for this phenomenon. Thus, the variation in synonymous substitution rates and the resulting unequal codon usage must be the consequence of selection against A and T in synonymous positions. Most of the variation in rates of synonymous substitution can be explained by the nucleotide composition in synonymous positions. Codon-anticodon interactions, dinucleotide frequencies, and contextual factors influence neither the rates of synonymous substitution nor codon usage. Interestingly, the nucleotide in the second position of codons (always a nonsynonymous position) was found to affect the rate of synonymous substitution. This finding links the rate of nonsynonymous substitution with the synonymous rate. Consequently, highly conservative proteins are expected to be encoded by genes that evolve slowly in terms of synonymous substitutions, and are consequently highly biased in their codon usage.

Human testicular lactate dehydrogenase-C gene is interrupted by six introns at positions homologous to those of LDH-A (muscle) and LDH-B (heart) genes

Human genomic clones containing parts of testis-specific lactate dehydrogenase-C gene of approximately 40 kilobases in length were isolated and characterized. The protein-coding sequence of human LDH-C gene is interrupted by six introns at positions homologous to those of mammalian LDH-A (muscle) and LDH-B (heart) genes, and exhibits 21%, 24% and 34% nucleotide differences with those of mouse LDH-C, human LDH-A and LDH-B genes, respectively.

Structure of the human lactate dehydrogenase B gene

Human genomic clones containing parts of the lactate dehydrogenase B (LDH-B) gene (approx. 25 kb in length) were isolated and characterized. The protein-coding sequence of human LDH-B gene is interrupted by six introns at codons nos. 42-43, 82, 140, 198, 237 and 278-279, and the positions of these introns are homologous to those of LDH-A genes from man and mouse. The 5' non-coding region of human LDH-B gene is interrupted by an intron six nucleotide residues upstream of the ATG translation-initiation site, whereas those of human and mouse LDH-A genes are interrupted at 24 nucleotide residues 5' to the ATG initiation codon. As is the case of LDH-A genes from man and mouse, there is no intron in the 3' non-coding region of human LDH-B gene.

Cancer-associated lactate dehydrogenase is a tyrosylphosphorylated form of human LDH-A, skeletal muscle isoenzyme

Cancer-associated lactate dehydrogenase is a tyrosylphosphorylated form of human skeletal muscle isoenzyme, since the partial amino acid sequences of human liver LDH-K/A protein were found to be identical with the known primary structure of human LDH-A isoenzyme and the LDH-A isoenzymes from human placenta and bovine muscle were shown to be tyrosylphosphorylated. This tyrosylphosphorylated LDH-K/A protein was also found to be complexed with 21 kD, 30 kD, and 56 kD proteins.

The cDNA and protein sequences of human lactate dehydrogenase B

Human lactate dehydrogenase B (LDH-B) cDNA was isolated and sequenced. The LDH-B cDNA insert consists of the protein-coding sequence (999 bp), the 5' (54 bp) and 3' (203 bp) non-coding regions, and the poly(A) tail (50 bp). The predicted sequence of 333 amino acid residues was confirmed by amino acid composition and/or sequence analyses of a total of 185 (56%) residues from tryptic peptides of human LDH-B protein. The nucleotide and amino acid sequences of the human LDH-B coding region show 68% and 75% homologies respectively with those of the human LDH-A. The peptide map and amino acid composition data have been deposited as Supplementary Publication SUP 50139 (7 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies are available on prepayment [see Biochem. J. (1987) 241, 5].

Inhibition of the reactivation of acid-dissociated lactate dehydrogenase isoenzymes by their aminoterminal CNBr fragments

The catalytic activity of lactate dehydrogenase isoenzymes (LDH) depends on their tetrameric structure. Stabilization of this quaternary structure is achieved by interaction of the N-terminal part of one subunit with the C-terminal region of the other subunit. The N-terminal peptides from pig M-LDH and H-LDH which are responsible for this stabilization were obtained by CNBr-fragmentation and purification on reversed-phase HPLC. The effect of these peptides on the formation of the quaternary structure of LDH-isoenzymes was investigated by monitoring the reconstitution of the catalytic activity after acid-dissociation. Low concentrations of the N-terminal peptides led to an increased, and high concentrations to a decreased yield of reconstituted LDH activity. The effects of these two peptides were isoenzyme specific. The 32 residue peptide derived from M-LDH showed the highest effect when tested with M-LDH as target enzyme but only a poor effect with H-LDH. On the other side the 33 residue peptide generated from H-LDH showed a moderate effect with both isoenzymes. The effects of the N-terminal LDH peptides are antagonized by the coenzymes NAD+ and NADH. The most significant influence was observed with NAD+ in the M-LDH peptide-M-LDH enzyme system. Comparison of the properties of the reactivation antagonists isolated from human origin with the N-terminal CNBr-peptides of LDH revealed identity in all essential properties, suggesting that the former peptides are generated by degradation of LDH.

Molecular isolation and sequence determination of the cDNA for the mouse sperm-specific lactate dehydrogenase-X gene

Several cDNA clones for the mouse lactate dehydrogenase-X (LDH-X), a sperm-specific glycolytic enzyme, were isolated from mouse testicular cDNA libraries constructed in the bacteriophage vectors, lambda gt11 and gt10. The largest cDNA clone contains an insert of 1135 base pairs in length and an open reading frame that encodes a 332 amino acid polypeptide with a molecular weight of 35.89 kD. The deduced amino acid sequence of this protein is in close agreement with the published sequence of mouse LDH-X obtained by direct protein sequencing. Northern analysis of RNA isolated from different tissues detected a single size mRNA of 1.5 kilobases in mouse testis but not in brain or liver. The Ldh-x structural gene was estimated to be about 12 kb in size as demonstrated by Southern hybridization analysis of mouse genomic DNA using the full-length cDNA as a probe.

Molecular cloning and nucleotide sequence of the cDNA for sperm-specific lactate dehydrogenase-C from mouse

Mouse sperm-specific lactate dehydrogenase-C (LDH-C) cDNA was cloned and sequenced from lambda gt11 expression library. The LDH-C cDNA insert of 1236 bp consists of the protein-coding sequence (999 bp), the 5' (54 bp) and 3' (113 bp) non-coding regions, and the poly(A) tail (70 bp). The Northern blot analysis of poly(A)-containing RNAs from mouse testes and liver indicates that the LDH-C gene is expressed in testes but not in liver, and that its mRNA is approx. 1400 nucleotides in length. The nucleotide and amino acid sequences of the mouse LDH-C cDNA show 73% and 72% homologies, respectively, with those of the mouse LDH-A. The Southern blot analysis of genomic DNAs from mouse liver and human placenta indicates the presence of multiple LDH-C gene-related sequences.

Nucleotide sequence and characteristics of the gene for L-lactate dehydrogenase of Thermus caldophilus GK24 and the deduced amino-acid sequence of the enzyme

The gene for L-lactate dehydrogenase (LDH) (EC 1.1.1.27) of Thermus caldophilus GK24 was cloned in Escherichia coli using synthetic oligonucleotides as hybridization probes. The nucleotide sequence of the cloned DNA was determined. The primary structure of the LDH was deduced from the nucleotide sequence. The deduced amino acid sequence agreed with the NH2-terminal and COOH-terminal sequences previously reported and the determined amino acid sequences of the peptides obtained from trypsin-digested T. caldophilus LDH. The LDH comprised 310 amino acid residues and its molecular mass was determined to be 32,808. On alignment of the whole amino acid sequences, the T. caldophilus LDH showed about 40% identity with the Bacillus stearothermophilus, Lactobacillus casei and dogfish muscle LDHs. The T. caldophilus LDH gene was expressed with the E. coli lac promoter in E. coli, which resulted in the production of the thermophilic LDH. The gene for the T. caldophilus LDH showed more than 40% identity with those for the human and mouse muscle LDHs on alignment of the whole nucleotide sequences. The G + C content of the coding region for the T. caldophilus LDH was 74.1%, which was higher than that of the chromosomal DNA (67.2%). The G + C contents in the first, second and third positions of the codons used were 77.7%, 48.1% and 95.5% respectively. The high G + C content in the third base caused extremely non-random codon usage in the LDH gene. About half (48.7%) the codons in the LDH gene started with G, and hence there were relatively high contents of Val, Ala, Glu and Gly in the LDH. The contents of Pro, Arg, Ala and Gly, which have high G + C contents in their codons, were also high. Rare codons with U or A as the third base were sometimes used to avoid the TCGA sequence, the recognition site for the restriction endonuclease, TaqI. Two TCGA sequences were found only in the sequence of CTCGAG (XhoI site) in the sequenced region of the T. caldophilus DNA. There were three segments with similar sequences in the two 5' non-coding regions, probably the promoter and ribosome-binding regions, of the genes for the T. caldophilus LDH and the Thermus thermophilus 3-isopropylmalate dehydrogenase.

A postmeiotically expressed clone encodes lactate dehydrogenase isozyme X

We have analysed by the DNA sequencing one of the cDNA clones, pPM459, to mRNA abundant in spermatids of mice. This clone contained 535 base pair nucleotides with a coding region for 139 amino acids and a 3' untranslated region including a single polyadenylation signal. Screening of the protein database revealed that the deduced amino acid sequence highly matched the carboxyl terminal residues 192-330 of mouse lactate dehydrogenase isozyme X (LDH-X). Taken together with our previous report which showed transcription of the message hybridizing to pPM459 after meiosis, it was demonstrated that LDH-X mRNA synthesis continued during the postmeiotic phase in spermatogenesis.

Nucleotide sequence of the putative regulatory region of mouse lactate dehydrogenase-A gene

The nucleotide sequence of approx. 3 kilobases including the regulatory region, a non-coding exon and the first protein-coding exon from mouse lactate dehydrogenase-A (LDH-A) gene has been determined. The putative initiation sites of transcription and translation were deduced by comparing the nucleotide sequence of mouse LDH-A gene with those of a mouse LDH-A processed pseudogene and the LDH-A full-length cDNAs from rat and human. The tentative TATA and CAAT boxes, and the hexanucleotides CCGCCC have been identified. The sequence of AAATCTTGCTCAA of mouse LDH-A gene has also been found to show striking homology to the cyclic AMP-responsive sequences of eukaryotic genes regulated by cyclic AMP. It has been reported previously that the protein-coding sequence of mouse LDH-A gene is interrupted by six introns and the 3' untranslated sequence of 485 nucleotides is not interrupted [Li, Tiano, Fukasawa, Yagi, Shimiza, Sharief, Nakashima & Pan (1985) Eur. J. Biochem. 149, 215-225]. An additional intron of 1653 base-pairs was found in the 5' untranslated sequence of 101 nucleotides at 24 nucleotides upstream to the translation start site. Thus, mouse LDH-A gene containing seven introns spans approx. 11 kilobases and its length of mature mRNA is 1582 nucleotides, excluding the poly(A) tail.

13C-NMR and transient kinetic studies on lactate dehydrogenase [Cys(13CN)165]. Direct measurement of a rate-limiting rearrangement in protein structure

Chemical modification of cysteine-165 in pig heart lactate dehydrogenase to produce lactate dehydrogenase [Cys(13CN)165] introduces an covalently bound, enriched 13C probe at a position adjacent to the active cen. The signal from the thiocyanate probe is clearly visible at 47 ppm relative to dioxane. On formation of binary complexes with NAD+ and NADH, no signal change is detected. Formation of the ternary complexes E-NADH-oxamate and E-NAD+-oxalate results in an upfield shift of the signal of 1.2 ppm. These results interpreted as demonstrating that binding of the substrate analogue induces a conformational change a position adjacent to the active centre. Exchange experiments in which the enzyme is poised in dynamic equilibrium between binary and ternary complexes show that the rate at which the probe senses a change environment is the same as the kinetically observed unimolecular event which limits the enzyme-catalyst reduction of pyruvate. The two processes show the same dependence on temperature, solvent composition and pH. These results indicate that the rate-limiting isomerisation corresponds to a rearrangement of the protein in the region of cysteine-165.