Chronic lactate exposure promotes cardiomyocyte cytoskeleton remodelling

We investigated the effect of growing on lactate instead of glucose in human cardiomyocyte assessing their viability, cell cycle activity, oxidative stress and metabolism by a proteomic and metabolomic approach. In previous studies performed on elite players, we found that adaptation to exercise is characterized by a chronic high plasma level of lactate. Lactate is considered not only an energy source but also a signalling molecule and is referred as "lactormone"; heart is one of the major recipients of exogenous lactate. With this in mind, we used a cardiac cell line AC16 to characterize the lactate metabolic profile and investigate the metabolic flexibility of the heart. Interestingly, our data indicated that cardiomyocytes grown on lactate (72 h) show change in several proteins and metabolites linked to cell hypertrophy and cytoskeleton remodelling. The obtained results could help to understand the effect of this metabolite on heart of high-performance athletes.

Preliminary results indicate that regular training induces high protection against oxidative stress in basketball players compared to soccer

In elite athlete several metabolic changes occur during regular training. These modifications are associated with changes in blood metabolic profile and can lead to adaptive mechanisms aimed at establish a new dynamic equilibrium, which guarantees better performance. The goal of this study was to characterize the plasma metabolic profile and redox homeostasis, in athletes practicing two different team sports such as soccer and basketball in order to identify potential metabolic pathways underlying the differences in training programs. A cohort of 30 male, 20 professional players (10 soccer and 10 basketballs) and 10 sedentary males as control were enrolled in the study. Plasma redox balance, metabolites and adiponectin were determined. The results show low levels of oxidative species (25.5%), with both high antioxidant capacity (17.6%) and adiponectin level (64.4%) in plasma from basketball players, in comparison to soccer players. Metabolic analysis indicates in basketball players a significant high plasma level of amino acids Valine and Ornithine both involved in redox homeostasis and anti-inflammatory metabolism.

Redox Homeostasis and Metabolic Profile in Young Female Basketball Players during in-Season Training

BACKGROUND

Most studies on oxidative stress markers and antioxidant levels have been conducted in male athletes, although female participation in sport has increased rapidly in the past few decades. In particular, it could be important to assess oxidative stress markers in relation to the training load because the anaerobic path becomes predominant in high-intensity actions.

METHODS

Ten female professional basketball players, performing five 2 h-lasting training sessions per week, and 10 sedentary control women were investigated. Capillary blood and saliva samples were collected in the morning before the training session. The antioxidant capacity and the levels of reactive oxygen metabolites on plasma were determined measuring Reactive Oxygen Metabolite and Biological Antioxidant Potential (d-ROMs and the BAP Test). Salivary cortisol was detected by using commercial enzyme-linked immunosorbent assay kit.

RESULTS

The antioxidant capacity (BAP value) was significantly higher in elite basketball players (21.2%; p < 0.05). Conversely, cortisol (51%; p < 0.009) and the levels of oxidative species (d-ROM, 21.9%; p < 0.05) showed a significant decrease in elite athletes.

Anti-inflammatory properties of the marine plant Posidonia oceanica (L.) Delile

ETHNOPHARMACOLOGICAL RELEVANCE

Posidonia oceanica (L.) Delile is an endemic seagrass of the Mediterranean Sea whose use has been documented as a traditional herbal remedy for diabetes and hypertension. Our recently described Posidonia oceanica leaves extract is a phytocomplex endowed with interesting bioactivities, including the inibitory property on human cancer cell migration.

AIM OF THE STUDY

The aim of this study was to investigate the anti-inflammatory effects of P. oceanica extract underlying its mechanism of action.

MATERIALS AND METHODS

We explored the anti-inflammatory effects of P. oceanica extract on RAW264.7 murine macrophages activated by LPS. We investigated the reactive oxygen species (ROS) and nitric oxide (NO) production and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Then, we examined P. oceanica extract role on the regulation of NF-κB signaling pathway.

RESULTS

P. oceanica phytocomplex exhibited a strong ability to inhibit oxidative stress by affecting the production of both ROS and NO and to reduce iNOS and COX-2 levels. In addition, it was evidenced its anti-inflammatory role via inhibiting NF-κB signaling pathway through modulation of ERK1/2 and Akt intracellular cascades.

CONCLUSIONS

Our results recognize an anti-inflammatory role of P. oceanica phytocomplex particularly emphasizing its cell safe mechanism of action. In conclusion, the marine plant P. oceanica may be of great interest for scientific research as a source of promising molecules for designing alternative strategies to the conventional treatment of inflammatory diseases.

Oxidative stress in exercise training: the involvement of inflammation and peripheral signals

The evidence about the health benefits of regular physical activity is well established. Exercise intensity is a significant variable and structured high-intensity interval training (HIIT) has been demonstrated to improve both whole-body and skeletal muscle metabolic health in different populations. Conversely, fatigue accumulation, if not resolved, leads to overwork, chronic fatigue syndrome (CFS), overtraining syndrome up to alterations of endocrine function, immune, systemic inflammation, and organic diseases with health threat. In response to temporary increases in stress during training, some athletes are unable to maintain sufficient caloric intake, thus suffering a negative energy balance that causes further stress. The regulation of the energy balance is controlled by the central nervous system through an elaborate interaction of the signalling that involves different tissues such as leptin, adiponectin and ghrelin whose provide important feedback to the hypothalamus to regulate the energy balance. Although exercise-induced reactive oxygen species are required for normal force production in muscle, high levels of ROS appear to promote contractile dysfunction. However, a high level of oxidative stress in may induce a rise in inflammatory markers and a disregulation in expression of adiponectin, leptin and grelin.

Targeting LMW-PTP to sensitize melanoma cancer cells toward chemo- and radiotherapy

Tumor resistance to apoptosis is one the main causes of anticancer treatment failure. Previous studies showed that LMW‐PTP overexpression enhances resistance of cancer cells to traditional anticancer drugs. Today, the role of LMW‐PTP in inducing resistance to apoptosis in melanoma cells remains to be elucidated. Experimental setting include MTT assay, Annexin V/Pi method, and colony assay to assess whether silencing of LMW‐PTP improves the sensitivity of A375 to dacarbazine, 5‐FU, and radiotherapy. Pharmacological targeting of LMW‐PTP was obtained using Morin, a LMW‐PTP inhibitor. The ability of Morin to improve the effectiveness of anticancer drugs and radiotherapy was also studied. Moreover, PC3 cells were used as an alternative cellular model to confirm the data obtained with melanoma cells. We found that LMW‐PTP silencing improves the effectiveness of dacarbazine, 5‐FU, and radiotherapy. Identical results were obtained in vivo when Morin was used to target LMW‐PTP. We demonstrated that Morin synergizes with dacarbazine, improving its cytotoxic activity. However, we showed that the combined treatment, Morin‐anticancer drug, does not affect the viability of noncancerous cells. Knockdown of LMW‐PTP sensitizes also PC3 cells to docetaxel and radiotherapy. In conclusion, we showed that LMW‐PTP targeting improves effectiveness of anticancer drugs used for treatment of melanoma. Moreover, our results suggest that Morin could be used as adjuvant to improve the outcome of patients affected by metastatic melanoma.

The expression of low molecular weight protein tyrosine phosphatase is up-regulated in 1,2-dimethylhydrazine-induced colon tumours in rats

Recent studies have assessed the role of low molecular weight protein tyrosine phosphatase (LMW-PTP) in cell transformation and tumour onset and progression, observing a significant increase in the expression of LMW-PTP mRNA and protein in human breast, colon, bladder and kidney tumour samples. Moreover, its enhanced expression is generally prognostic of a more aggressive cancer. To better understand the role of this protein during colon carcinogenesis and to study whether its overexpression is also observed in earlier phases of carcinogenesis, we studied its expression in colon tumours, induced in rats by treatment with 1,2-dimethylhydrazine (DMH), an animal model that resemble the sequential formation of histopathological lesions of spontaneous carcinogenesis in humans. The results show a significant increase in LMW-PTP expression in adenocarcinomas, suggesting that this phenomenon is associated with the onset of malignancy. Moreover a significant overexpression of LMW-PTP transcript is associated with tumours originating in the proximal (right) part of the colon, confirming an observation already reported for human colon cancer.

Up-regulated expression of low molecular weight protein tyrosine phosphatases in different human cancers

Protein tyrosine phosphorylation, mediated by the balanced action of tyrosine kinases and phosphatases, contributes to the regulation of the growth, migration, and invasion of normal and malignant cells. Among tyrosine phosphatases, low molecular weight protein tyrosine phosphatases (LMW-PTP) have been recognized as a possible "positive factor" in tumour onset and progression. The aim of this work was to assess whether LMW-PTP are differentially expressed in normal and malignant tissues. Using real-time PCR analysis we evaluated the expression levels of total LMW-PTP mRNA in surgical samples of breast, colon and lung cancers (63, 60, and 58, respectively), and in their paired adjacent not affected tissues. Moreover, the same analysis was carried out on a group of neuroblastomas (25 cases). Significant correlations between LMW-PTP overexpression and the most common clinical-pathological features of cancers exist. In colon cancer and neuroblastoma increased total LMW-PTP mRNA expression correlates with unfavourable outcome. While LMW-PTP mRNA expression increases in tumour samples, the relative contribution of the different isoforms does not change. Our findings indicate that LMW-PTP can be considered an oncogene as it is overexpressed in different tumour types and suggests that LMW-PTP enhanced expression is generally prognostic for a more aggressive cancer.

ACYP1 gene possesses two alternative splicing forms that induce apoptosis

In human cell lines two products of the ACYP1 gene were detected by RT-PCR. In addition to the expected amplicon corresponding to the CT form of acylphosphatase (320 bp) a second unexpected one (400 bp) was characterized as the result of an alternative splicing in which an extra 79 bp long exon is inserted between the two known exons. This new product, indicated as CTsv, was cloned and expressed. We performed the ectopic expression of the two alternative splicing forms. Both CT and CTsv products were able to induce a proapoptotic effect when expressed in HeLa cell line, despite the fact that the CTsv protein did not show any acylphosphatase activity.

Characterization of a novel Drosophila melanogaster acylphosphatase

Analysis of the Drosophila melanogaster EST database led to the characterization of a novel acylphosphatase (AcPDro2). This is coded by the CG18505 (Acyp2) gene and is clearly distinct from a previously described AcPDro coded by the CG16870 (Acyp) gene from D. melanogaster. The two proteins show a 60% homology with both vertebrate isoenzymes. All the residues involved in the catalytic mechanism are conserved. AcPDro2 is a stable enzyme with a correct globular folded structure. Its activity on benzoylphosphate shows higher K(cat) but lower K(m) with respect to AcPDro. It is possible that AcPDro and AcPDro2 genes are not the direct ancestor of MT and CT vertebrate isoenzymes.

Thiolation of low-Mr phosphotyrosine protein phosphatase by thiol-disulfides

Thiol-disulfides cause a time- and a concentration-dependent inactivation of the low-M(r) phosphotyrosine protein phosphatase (PTP). We demonstrated that six of eight enzyme cysteines have similar reactivity against 5,5'-dithiobis(nitrobenzoic acid): Their thiolation is accompanied by enzyme inactivation. The inactivation of the enzyme by glutathione disulfide also is accompanied by the thiolation of six cysteine residues. Inorganic phosphate, a competitive enzyme inhibitor, protects the enzyme from inactivation, indicating that the inactivation results from thiolation of the essential active-site cysteine of the enzyme. The inactivation is reversed by dithiothreitol. Although all PTPs have three-dimensional active-site structures very similar to each other and also have identical reaction mechanisms, the thiol group contained in the active site of low-M(r) PTP seems to have lower reactivity than that of other PTPs in the protein thiolation reaction.

Acylphosphatase expression during macrophage differentiation and activation of U-937 cell line

The two acylphosphatase isoenzymes (muscle type and common type) are differently involved in cell differentiation processes. In this paper we investigate the expression of the two isoenzymes during macrophage differentiation and activation. The U-937 human promonocytic cell line is a model for cell differentiation induced by the tumor promoter phorbol myristic acetate (PMA). Here we show that only the expression of the muscle type acylphosphatase increases during U-937 differentiation and macrophage activation, confirming that the two isoenzymes are differently regulated. Moreover, we determined, in the same conditions, the level of specific mRNA. Results show that after an initial two-fold decrease during PMA stimulation, the muscle type acylphosphatase mRNA levels remain constant also after the treatment with lipopolysaccharide and gamma-interferon, treatments that lead to macrophage activation. It is possible that post-transcription regulation is responsible for the regulation of muscle type acylphosphatase in the cell during differentiation and macrophage activation.

The inactivation mechanism of low molecular weight phosphotyrosine-protein phosphatase by H2O2

Low molecular weight phosphotyrosine-protein phosphatase (LMW-PTP) shares no general sequence homology with other PTPs, although it has an active site sequence motif CXXXXXR and a reaction mechanism identical to those of all PTPs. The main function of this enzyme is the down-regulation of platelet-derived growth factor and insulin receptors. Both human LMW-PTP isoenzymes are inactivated by H2O2. The enzymes are protected from inactivation by Pi, a competitive inhibitor, suggesting that the H2O2 reaction is directed to active site. Analysis of free thiols performed on the inactivated enzymes demonstrates that only two out of the eight LMW-PTP cysteines are modified. Time-course high performance liquid chromatography-electrospray mass spectrometry, together with specific radiolabeling and tryptic fingerprint analyses, enables us to demonstrate that H2O2 causes the oxidation of Cys-12 and Cys-17 to form a disulfide bond. Because both residues are localized into the active site region, this modification inactivates the enzyme. Fluorescence spectroscopy experiments suggest that the fold of the enzyme is modified during oxidation by H2O2. Because a physiological concentration of H2O2 produces enzyme inactivation and considering that the activity is restored by reduction with low molecular weight thiols, we suggest that oxidative stress conditions and other processes producing hydrogen peroxide regulate the LMW-PTP in the cell.

Different in vitro and in vivo activity of low Mr phosphotyrosine protein phosphatase on epidermal growth factor receptor

Low Mr phosphotyrosine protein phosphatase is a cytosolic enzyme which dephosphorylates platelet-derived growth factor and insulin receptor in vivo, thus reducing cellular mitogenic response to such growth factors. Following cell stimulation with platelet-derived growth factor the phosphatase undergoes a redistribution from the citosol to the Triton X-100-insoluble fraction where its activity upon the growth factor receptor is intense. Previous research uncovered evidence that low Mr phosphotyrosine protein phosphatase dephosphorylates the epidermal growth factor receptor in vitro. Here we demonstrate that in vivo the enzyme is not active on the phosphorylated epidermal growth factor receptor and it does not influence the mitogenic response of cells. Since the enzyme distribution is not affected by epidermal growth factor stimulation, involvement of a recruitment mechanism in the definition of low Mr phosphotyrosine protein phosphatase substrate specificity is hypothesized.

Low molecular weight phosphotyrosine protein phosphatase translocation during cell stimulation with platelet-derived growth factor

Low Mr phosphotyrosine protein phosphatase (PTP) is a cytosolic enzyme whose activity upon platelet-derived growth factor (PDGF) and insulin receptors has been demonstrated in vivo. In our study we demonstrate that this enzyme, both naturally expressed and overexpressed in NIH/3T3 fibroblasts, translocates from the cytosol to the Triton X-100 insoluble fraction following stimulation with PDGF. It emerges that the phosphorylation of a defined population of PDGF receptors, which is localized in this fraction and seems to be endowed with peculiar features and functions, is particularly affected by low Mr PTP overexpression.

Cloning, expression and characterisation of a new human low Mr phosphotyrosine protein phosphatase originating by alternative splicing

RT-PCR experiments on RNA from K562 and HepG2 cells and from human placenta led to the isolation of a novel cDNA, a further alternative splicing product of the primary transcript of low Mr phosphotyrosine phosphatase (LMW-PTP), already known to produce isoforms 1 and 2. This new transcript represents 15-20% of the total LMW-PTP mRNA in the cell. This novel cDNA codifies for a protein that we have named SV3 (splicing variant 3): the deduced protein sequence presents the first 49 residues identical to those of isoform 1, followed by 24 unrelated amino acids, due to a frameshift introduced at the novel exon-exon boundary. The SV3 protein, expressed in E. coli is enzymatically inactive, most probably because unfolded, as suggested by far-UV circular dichroism (CD) experiments. SV3 protein appears to possess the characteristics of an unstructured polypeptide chain lacking the packing of side chain residues and the secondary structure level that are typical of globular proteins. This protein could represent an inactive variant of the human LMW-PTP.

Expression, purification and preliminary crystal analysis of the human low Mr phosphotyrosine protein phosphatase isoform 1

The genes of the human low Mr phosphotyrosine protein phosphatase (PTPase) isoforms 1 (IF1) and 2 (IF2) were isolated by screening a human placenta cDNA library, cloned in pGEX and expressed in E. coli as fusion proteins with glutathione S-transferase. The recombinant proteins were purified by a rapid one-step procedure allowing each enzyme to purify with high final yield and specific activity. This result is important for IF1, whose purification from natural sources is difficult, due to precipitation propensity, thus hindering structural studies. The enzymes obtained showed kinetic parameters very similar to those previously determined for the enzymes purified by classical procedures from both human erythrocytes and rat liver. These recombinant enzymes can therefore be used in place of those purified from natural sources for every purpose. IF1 and IF2 crystals were also grown. IF1 crystals were X-ray-grade, diffracted to better than 2.4 A and were suitable for high resolution X-ray structure determination.

The 5'-untranslated region of the human muscle acylphosphatase mRNA has an inhibitory effect on protein expression

The cDNA of the human muscle type acylphosphatase was isolated and characterized. The mRNA presents a very long 5'-untranslated region, covering the first half of the molecule: 175 bases of this part were cloned and prediction of the possible secondary structure showed that a very stable stem-loop structure could be formed in that region. Moreover, an additional AUG triplet was found upstream of the start codon of the protein, defining an open reading frame of 60 codons which overlapped that of acylphosphatase. The possible regulatory effect on translation of this part of the mRNA molecule was studied by means of transient transfection experiments: a 10-fold decrease in the expression of a reporter protein and a dramatic decrease in the corresponding mRNA was observed, due to the presence of the 5'-untranslated region of acylphosphatase mRNA. Mutagenesis of the upstream AUG triplet eliminated mRNA instability, leading to the hypothesis that the product of the upstream open reading frame could play a role in this mechanism.

Expression of acylphosphatase in Saccharomyces cerevisiae enhances ethanol fermentation rate

Previous experiments in vitro have demonstrated the ability of acylphosphatase to increase the rate of glucose fermentation in yeast. To evaluate the possibility of increasing fermentation in vivo also, a chemically synthesized DNA sequence coding for human muscle acylphosphatase was expressed at high level in Saccharomyces cerevisiae. Ethanol production was measured in these engineered strains in comparison with a control. Acylphosphatase expression strongly increased the rate of ethanol production both in aerobic and anaerobic culture. This finding may be potentially important for the development of more efficient industrial fermentation processes.

Differential modulation of expression of the two acylphosphatase isoenzymes by thyroid hormone

The modulation of expression of the skeletal muscle and erythrocyte acylphosphatase isoenzymes by thyroid hormone has been investigated. Our results indicate a differential regulation of the two enzymic isoforms by tri-iodothyronine (T3) in K562 cells in culture: an increase in the specific mRNA during T3-stimulation is shown only for the skeletal muscle isoenzyme. A fast and transient T3 induction of the accumulation of the specific mRNA can be observed, reaching a maximum 8 h after hormone treatment and then rapidly decreasing almost to the steady-state level after 24 h. A nuclear run-on assay was performed to explore the mechanisms of this regulation. These studies indicate that T3 induction of skeletal muscle acylphosphatase mRNA is due, at least in part, to a fast and transient increase in the rate of gene transcription, within 4 h after hormone administration. A very rapid decrease is then observed within a further 2 h. T3-dependent accumulation of the mRNA for the skeletal muscle acylphosphatase requires ongoing protein synthesis, as confirmed by inhibition with cycloheximide or puromycin. These findings indicate that the transcriptional regulation of the gene may be indirect.

Cloning and expression of the cDNA coding for the erythrocyte isoenzyme of human acylphosphatase

Three independent cDNAs coding for the erythrocyte isoform of human acylphosphatase were isolated and characterized. All the clones were incomplete at the 5' end, but Northern blot analysis using the cDNA as a probe showed the presence of an unusually long mRNA 5'-untranslated region. The transcript was present in a variety of human cell lines of different origins, although at different levels. Southern blot analysis on DNA from different individuals revealed a simple hybridization pattern. Large amounts of pure enzyme with kinetic characteristics very similar to those of the native protein were expressed in E. coli.

Chemical synthesis and expression of a gene coding for human muscle acylphosphatase

A DNA sequence coding for human muscle acylphosphatase has been constructed using 16 chemically synthesized oligonucleotides. The 300-bases long DNA sequence has been cloned in the pT7.7 Escherichia coli expression vector and in the pYEpsec1 Saccharomyces cerevisiae expression vector. In both cases a high level of expression of acylphosphatase has been observed. The recombinant proteins have been purified to homogeneity and assayed in comparison with the natural protein, using benzoylphosphate as a substrate and phosphate as a competitive inhibitor. The recombinant enzymes expressed in the two microorganisms maintain the kinetic properties of the natural protein. In addition, NMR analysis shows that the gross fold of the two recombinant enzymes is correct.

Differential role of four cysteines on the activity of a low M(r) phosphotyrosine protein phosphatase

In this paper we describe the construction of five mutants of a bovine liver low M(r) phosphotyrosine protein phosphatase (PTPase) expressed as a fusion protein with the maltose binding protein in E. coli. Almost no changes in the kinetic parameters were observed in the fusion protein with respect to the native PTPase. Using oligonucleotide-directed mutagenesis Cys-17, Cys-62 and Cys-145 were converted to Ser while Cys-12 was converted to both Ser and Ala. The kinetic properties of the mutants, using p-nitrophenyl phosphate as substrate, were compared with those of the normal protein fused with the maltose binding protein of E. coli; both of the Cys-12 mutants showed a complete loss of enzymatic activity while the specific activity of the Cys-17 mutant was greatly decreased (200-fold). The Cys-62 mutant showed a 2.5-fold decrease in specific activity, while the Cys-145 mutant remained almost unchanged. These data confirm the involvement of Cys-12 and Cys-17 in the catalytic site and suggest that Cys-62 and Cys-145 mutations may destabilise the structure of the enzyme.

Erythropoietin rapidly induces tyrosine phosphorylation in the human erythropoietin-dependent cell line, UT-7

UT-7 is a human megakaryoblastic cell line capable of growing in interleukin-3, granulocyte-macrophage colony-stimulating factor, or erythropoietin (Epo) (Cancer Res 51:341, 1991). We used this cell line and a selected Epo-dependent subcell line (UT-7/Epo) to study the early signal transduction events induced by Epo. When UT-7 cells were exposed to Epo, tyrosine phosphorylation of several proteins (with molecular weight equivalent to that of p85, p110, and p145) was observed. Protein phosphorylation occurred in both a dose- and time-dependent manner. p85 showed a marked increase in phosphotyrosine content within 30 seconds; maximal phosphorylation was observed at 1 minute. Subsequently, tyrosine phosphorylation of p110 and p145 was observed, beginning at 1 minute and reaching plateau at 5 minutes. The degree of phosphorylation of these three proteins gradually decreased thereafter. In addition, in UT-7/Epo cells, Epo induced tyrosine phosphorylation of other proteins that were not observed in Epo-induced UT-7 cells. The concentration of Epo required to induce tyrosine phosphorylation was in the same range of concentration required to stimulate cell growth. Epo was also able to activate p21ras as measured by exchange of guanosine diphosphate for guanosine triphosphate. These data show that tyrosine phosphorylation and P21ras activation are early signals in the Epo-induced mitogenic pathway.

Chemical synthesis and expression of a gene coding for bovine liver phosphotyrosine-protein phosphatase

A chemically synthesized polynucleotide sequence coding for bovine liver low molecular weight acid phosphatase (which possesses phosphotyrosine-protein phosphatase activity) has been cloned in a E. coli expression vector. The recombinant protein retains correct affinity for substrate and inhibitors but shows a reduced specific activity.

Horse brain acylphosphatase: purification and characterization

Two structurally different acylphosphatases found in horse brain were purified; they were not immunologically related. The molecular masses were almost identical and the kinetic parameters were rather similar. The data reported indicate that one of the purified brain acylphosphatases and an enzyme, previously isolated from horse muscle, are the same protein. The presence of this acylphosphatase form in the brain has not been reported before. The other acylphosphatase seemed to be the same as the enzyme which had been purified from calf brain and partially characterized by Diederich and Grisolia [(1969) J. Biol. Chem. 244, 2412-2417]. Furthermore, this enzyme seems to be identical to the acylphosphatase recently purified in our laboratory from human erythrocytes.

Guinea pig acylphosphatase: the amino acid sequence

We determined the primary structure of guinea pig skeletal muscle acylphosphatase, using the high degree of homology with several vertebrate acylphosphatases to obtain correct alignment of the complete series of tryptic peptides. Their sequences were obtained mainly by Edman degradation; FAB mass spectrometry was used to identify the acyl group blocking the NH2-terminal residue and to elucidate the structure of the NH2-terminal tryptic peptide. The comparison among acylphosphatase sequences from skeletal muscle of several vertebrate species is presented and discussed.