Intermediate metabolism of aerobic spores. V. The purification and properties of L-alanine dehydrogenase

Two different alanine dehydrogenases from Geobacillus kaustophilus: Their biochemical characteristics and differential expression in vegetative cells and spores

Two putative alanine dehydrogenase (AlaDH) genes (GK2752 and GK3448) were found in the genome of a thermophilic spore-forming bacterium, Geobacillus kaustophilus. The amino acid sequences deduced from the two genes showed mutually high homology (71%), and the phylogenetic tree based on the amino acid sequences of the two putative AlaDHs and the homologous proteins showed that the two putative AlaDH genes (GK2752 and GK3448) belong to different groups. Both of the recombinant gene products exhibited high NAD+-dependent AlaDH activity and were purified to homogeneity and characterized in detail. Both enzymes showed high stability against low and high pHs and high temperatures (70 °C). Kinetic analyses showed that the activities of both enzymes proceeded according to the same sequentially ordered Bi-Ter mechanism. X-ray crystallographic analysis showed the two AlaDHs to have similar homohexameric structures. Notably, GK3448-AlaDH was detected in vegetative cells of G. kaustophilus but not spores, while GK2752-AlaDH was present only in the spores. This is the first report showing the presence of two AlaDHs separately expressed in vegetative cells and spores.

The Two-Component System ArlRS and Alterations in Metabolism Enable Staphylococcus aureus to Resist Calprotectin-Induced Manganese Starvation

During infection the host imposes manganese and zinc starvation on invading pathogens. Despite this, Staphylococcus aureus and other successful pathogens remain capable of causing devastating disease. However, how these invaders adapt to host-imposed metal starvation and overcome nutritional immunity remains unknown. We report that ArlRS, a global staphylococcal virulence regulator, enhances the ability of S. aureus to grow in the presence of the manganese-and zinc-binding innate immune effector calprotectin. Utilization of calprotectin variants with altered metal binding properties revealed that strains lacking ArlRS are specifically more sensitive to manganese starvation. Loss of ArlRS did not alter the expression of manganese importers or prevent S. aureus from acquiring metals. It did, however, alter staphylococcal metabolism and impair the ability of S. aureus to grow on amino acids. Further studies suggested that relative to consuming glucose, the preferred carbon source of S. aureus, utilizing amino acids reduced the cellular demand for manganese. When forced to use glucose as the sole carbon source S. aureus became more sensitive to calprotectin compared to when amino acids are provided. Infection experiments utilizing wild type and calprotectin-deficient mice, which have defects in manganese sequestration, revealed that ArlRS is important for disease when manganese availability is restricted but not when this essential nutrient is freely available. In total, these results indicate that altering cellular metabolism contributes to the ability of pathogens to resist manganese starvation and that ArlRS enables S. aureus to overcome nutritional immunity by facilitating this adaptation.

The ubiquitous pathogen Staphylococcus aureus is a serious threat to human health due to the continued spread of antibiotic resistance. This spread has made it challenging to treat staphylococcal infections and led to the call for new approaches to treat this devastating pathogen. One approach is to disrupt the ability of S. aureus to adapt to nutrient availability during infection. During infection, the host imposes manganese and zinc starvation on invading pathogens. However, the mechanisms utilized by Staphylococcus aureus to overcome this host defense are unknown. We report that ArlRS, a global staphylococcal virulence regulator, is important for resisting manganese starvation during infection. Loss of ArlRS does not prevent S. aureus from acquiring metals but instead renders the bacterium incapable of adapting to limited manganese availability. ArlRS mutants also have metabolic defects and a reduced ability to grow on amino acids. When using glucose as a carbon source S. aureus is more sensitive to manganese starvation and increases the expression of manganese transporters relative to when amino acids are provided suggesting a higher demand for manganese. These observations indicate that ArlRS contributes to resisting nutritional immunity by altering metabolism to reduce the staphylococcal demand for manganese.

L-Alanine dehydrogenase: a mechanism controlling the specificity of amino acid-induced germination of Bacillus cereus spores

O'Connor, R. J. (University of Wisconsin, Madison), and Harlyn O. Halvorson. L-Alanine dehydrogenase: A mechanism controlling the specificity of amino acid-induced germination of Bacillus cereus spores. J. Bacteriol. 82:706-713. 1961.-A study has been undertaken of the properties and specificity of germination of spores of Bacillus cereus strain T. In the absence of additional carbon sources, only l-alanine, l-alpha-NH(2)-n-butyric acid, and l-cysteine were effective germinating agents. The physical properties of germination, induced by l-alanine and l-alpha-NH(2)-n-butyric acid following extended heat shock, were in close agreement with those of l-alanine dehydrogenase. The specificity of the germination system, as well as amino acid deamination in vivo, support the view that l-alanine dehydrogenase activity is essential for germination and that the enzyme serves as the initial binding site for l-alanine in heat-shocked spores.

PURIFICATION AND PROPERTIES OF L-ALANINE DEHYDROGENASE FROM VEGETATIVE CELLS OF BACILLUS CEREUS

McCormick, Neil G. (University of Wisconsin, Madison), and Harlyn O. Halvorson. Purification and properties of l-alanine dehydrogenase from vegetative cells of Bacillus cereus. J. Bacteriol. 87:68-74. 1964.-The l-alanine dehydrogenase from vegetative cells of Bacillus cereus strain T has been purified approximately 200-fold. The enzyme has a molecular weight of 248,000 and a turnover number of 80,000 moles of substrate per min per mole of enzyme. The Michaelis constants for the substrates and the equilibrium constant for the reaction catalyzed by this enzyme are in close agreement with reported values for other l-alanine dehydrogenases. The kinetic properties of the enzyme purified from vegetative cells are identical to those of the enzyme isolated from spores of the same organism, but differ with respect to relative heat stability. Whereas spores contain a heat-resistant enzyme, vegetative cells contain, in addition, a heat-sensitive enzyme. No evidence was found to support the hypothesis that a molecular conversion type of phenomenon plays a role in the appearance of spore enzyme.

Alanine dehydrogenases from two Bacillus species with distinct thermostabilities: molecular cloning, DNA and protein sequence determination, and structural comparison with other NAD(P)(+)-dependent dehydrogenases

The gene encoding alanine dehydrogenase (EC 1.4.1.1) from a mesophile, Bacillus sphaericus, was cloned, and its complete DNA sequence was determined. In addition, the same gene from a moderate thermophile, B. stearothermophilus, was analyzed in a similar manner. Large parts of the two translated amino acid sequences were confirmed by automated Edman degradation of tryptic peptide fragments. Each alanine dehydrogenase gene consists of a 1116-bp open reading frame and encodes 372 amino acid residues corresponding to the subunit (Mr = 39,500-40,000) of the hexameric enzyme. The similarity of amino acid sequence between the two alanine dehydrogenases with distinct thermostabilities is very high (greater than 70%). The nonidentical residues are clustered in a few regions with relatively short length, which may correlate with the difference in thermal stability of the enzymes. Homology search of the primary structures of both alanine dehydrogenases with those of other pyridine nucleotide-dependent oxidoreductases revealed significant sequence similarity in the regions containing the coenzyme binding domain. Interestingly, several catalytically important residues in lactate and malate dehydrogenases are conserved in the primary structure of alanine dehydrogenases at matched positions with similar mutual distances.

Alanine dehydrogenase from Streptomyces fradiae. Purification and properties

Alanine dehydrogenase was purified to homogeneity from a cell-free extract of Streptomyces fradiae, which produces tylosin. The enzyme was purified 1180-fold to give a 21% yield, using a combination of hydrophobic chromatography and ion-exchange fast protein liquid chromatography. The relative molecular mass of the native enzyme was determined to be 210,000 or 205,000 by equilibrium ultracentrifugation or gel filtration, respectively. The enzyme is composed of four subunits, each of Mr 51,000. Using analytical isoelectric focusing the isoelectric point of alanine dehydrogenase was found to be 6.1. The Km were 10.0 mM for L-alanine and 0.18 mM for NAD+. Km values for reductive amination were 0.23 mM for pyruvate, 11.6 mM for NH4+ and 0.05 mM for NADH. Oxidative deamination of L-alanine proceeds through a sequential-ordered binary-ternary mechanism in which NAD+ binds first to the enzyme, followed by alanine, and products are released in the order ammonia, pyruvate and NADH.

Alanine dehydrogenase of the beta-lactam antibiotic producer Streptomyces clavuligerus

L-Alanine dehydrogenase was found in extracts of the antibiotic producer Streptomyces clavuligerus. The enzyme was induced by ammonia, and the level of induction was dependent on the extracellular concentraction. L-Alanine was the only amino acid able to induce alanine dehydrogenase. The enzyme was characterized from a 38-fold purified preparation. Pyruvate (Km = 1.1 mM), ammonia (Km = 20 mM) and NADH (Km = 0.14 mM) were required for the reductive amination, and L-alanine (Km = 9.1 mM) and NAD (Km = 0.5 mM) for the oxidative deaminating reaction. The aminating reaction was inhibited by alanine, serine and NADPH. Alanine inhibited uncompetitively with respect to NADH (Ki = 1.6 mM) and noncompetitively with respect to ammonia (Ki = 2.0 mM) and pyruvate (Ki = 3.0 mM). In the aminating reaction 3-hydroxypyruvate, glyoxylate and 2-oxobutyrate could partially (6--7%) substitute pyruvate. Alanine dehydrogenase from S. clavuligerus differed with respect to its molecular weight (92000) and its kinetic properties from those described for other microorganisms.

Purification and properties of alanine dehydrogenase from Bacillus sphaericus

1. The bacterial distribution of alanine dehydrogenase (L-alanine:NAD+ oxidoreductase, deaminating, EC 1.4.1.1) was investigated, and high activity was found in Bacillus species. The enzyme has been purified to homogeneity and crystallized from B. sphaericus (IFO 3525), in which the highest activity occurs. 2. The enzyme has a molecular weight of about 230 000, and is composed of six identical subunits (Mr 38 000). 3. The enzyme acts almost specifically on L-alanine, but shows low amino-acceptor specificity; pyruvate and 2-oxobutyrate are the most preferable substrates, and 2-oxovalerate is also animated. The enzyme requires NAD+ as a cofactor, which cannot be replaced by NADP+. 4. The enzyme is stable over a wide pH range (pH 6.0--10.0), and shows maximum reactivity at approximately pH 10.5 and 9.0 for the deamination and amination reactions, respectively. 5. Alanine dehydrogenase is inhibited significantly by HgCl2, p-chloromercuribenzoate and other metals, but none of purine and pyrimidine bases, nucleosides, nucleotides, flavine compounds and pyridoxal 5'-phosphate influence the activity. 6. The reductive amination proceeds through a sequential ordered ternary-binary mechanism. NADH binds first to the enzyme followed by ammonia and pyruvate, and the products are released in the order of L-ALANINE AND NAD+. The Michaelis constants are as follows: NADH (10 microM), ammonia (28.2 mM), pyruvate (1.7 mM), L-alanine (18.9 mM) and NAD+ (0.23 mM). 7. The pro-R hydrogen at C-4 of the reduced nicotinamide ring of NADH is exclusively transferred to pyruvate; the enzyme is A-stereospecific.

Partial purification and properties of Halobacterium cutirubrum L-alanine dehydrogenase

1. Halobacterium cutirubrum L-alanine dehydrogenase was purified approx. 100-fold. 2. It has a mol. wt. of 72 500, about one-third that of two well-studied alanine dehydrogenases from non-halophiles. 3. The activity of the enzyme increases with temperature up to 70 degrees C, but the protein itself is not thermostable. 4. In the reductive amination reaction, the enzyme is fully active in the presence of high concentrations of K+, Na+ or NH4+ and partially active with Cs+ or Li+, but for oxidative deamination it has an absolute requirement for K+.

Alanine dehydrogenase of the N2-fixing blue-green alga, Anabaena cylindrica

The L-alanine dehydrogenase (ADH) of Anabaena cylindrica has been purified 700-fold. It has a molecular weight of approximately 270,000, has 6 sub-units, each of molecular weight approximately 43,000, and shows activity both in the aminating and deaminating directions. The enzyme is NADH/NAD+ specific and oxaloacetate can partially substitute for pyruvate. The Kampp for NAD+ is 14 muM and 60 muM at low and high NAD concentrations respectively.

Stereochemistry of the hydrogen transfer to NAD catalyzed by (S)alanine dehydrogenase from Bacillus subtilis

The stereochemistry of the hydrogen transfer to NAD catalyzed by (S)alanine dehydrogenase [ (S)alanine: NAD oxidoreductase (EC 1.4.1.1) ] from B. subtilis was investigated. The label at C-2 of (S) [2,3--3H] alanine was enzymatically transferred to NAD, and the [4--3H]NADH produced isolated and the stereochemistry at C-4 investigated. It was found that the label was exclusively located at the (R) position which indicates that (S)alanine dehydrogenase is an A-type enzyme. This result was confirmed in an alternate way by reducing enzymatically [4--3H]NAD with non labeled (S)alanine and (S)alanine dehydrogenase and investigating the stereochemistry of the ]4--3H]NADH produced. As expected, the label was now exclusively located at the (S) position. This proves that (S)alanine dehydrogenase isolated from B. subtilis should be classified as an A-enzyme with regard to the stereochemistry of the hydrogen transfer to NAD.

Regulation of alanine dehydrogenase in Bacillus (licheniformis)

Cell extracts of Bacillus licheniformis were found to contain nicotinamide adenine dinucleotide (NAD)-dependent l-alanine dehydrogenase (ADH) (l-alanine: NAD oxidoreductase, EC 1.4.1.1). High specific activities (3.5 to 6.0 IU/mg of protein) were found in extracts of cells throughout growth cycles only when l-alanine served as the primary source of carbon or carbon and nitrogen. Specific activities were minimal (0.02 to 0.04 IU/mg of protein) during growth on glucose, but increased at least sevenfold during the first 5 h of postlogarithmic-phase metabolism. Addition of 10 mM glucose to cultures during logarithmic-phase growth on l-alanine resulted in a rapid decrease in enzyme activity. Addition of 20 mM l-alanine to cells near the completion of log-phase growth on glucose resulted in a 20-fold increase in ADH specific activity during less than one cell generation. Extracts of postlogarithmic-phase cells cultured on glucose, malate, l-glutamate, or Casamino Acids contained intermediate levels of ADH activity. The enzyme was partially purified from crude extracts of B. licheniformis, and apparent kinetic constants were estimated. A role for ADH in the catabolism of l-alanine to pyruvate during vegetative growth on l-alanine and during sporulation of cells cultured on glucose is proposed on the basis of these experimental results.

L-amino acid dehydrogenases in Bacillus subtilis spores

The presence of two kinds of l-amino acid dehydrogenase in resting spores of Bacillus subtilis was indicated. One of them was l-alanine dehydrogenase, which used only l-alanine as a substrate, and the other was nonspecific dehydrogenase, which used l-valine, l-isoleucine, l-leucine, and l-alanine (slightly) as substrates. Several properties of these dehydrogenases were compared.

Properties of fructose 1,6-diphosphate aldolases from spores and vegetative cells of Bacillus cereus

Fructose 1,6-diphosphate aldolase from cells of Bacillus cereus appears to be typical Class II aldolase as judged by its functional and physical properties. Spore and vegetative cell aldolase had similar enzymatic, immunochemical, and heat resistance properties in the absence of calcium, but they differed in their thermal stabilities in the presence of calcium, their Stokes' radii, their mobility in acrylamide gel electrophoresis, and their molecular weights. The pH optimum for both enzymes was 8.5, and their K(m) with respect to substrate was 2 x 10(-3)m. Highly purified spore and vegetative cell aldolases were both heat labile with half-lives of 4 min at 53 C and pH 6.4. In the presence of 3 x 10(-2)m solution of calcium ions, the stability of the spore protein increased 12-fold but the vegetative form became more heat labile. The enhanced stability of the spore aldolase was not diminished by dialysis or gel filtration but was lost after chromatography on diethylaminoethyl cellulose at pH 7.4. Aldolase from vegetative cells exists in an equilibrium mixture of two molecular weights, 115,000 and 79,000 in the approximate ratio of 1:4, respectively. The molecular weight of spore aldolase is 44,000. Spore aldolase was more mobile during electrophoresis than its vegetative cell counterpart because of its smaller size.

Purification and properties of L-alanine dehydrogenase from Desulfovibrio desulfuricans

The l-alanine dehydrogenase from cell-free extracts of Desulfovibrio desulfuricans was purified approximately 56-fold. The Michaelis constants for the substrates of the amination reaction and the pH optima for the reactions catalyzed by this enzyme closely agree with those reported for other l-alanine dehydrogenases. Pyruvate was found to inhibit the amination reaction. The enzyme was absolutely specific for l-alanine and nicotinamide adenine dinucleotide. Its sensitivity to para-chloromecuribenzoate suggests that sulfhydryl groups may be necessary for enzymatic activity. These extracts also contained a nicotinamide adenine dinucleotide phosphate-specific glutamic dehydrogenase which was separated from the l-alanine dehydrogenase during purification.

Timing of enzyme synthesis during outgrowth of spores of Bacillus cereus. I. Ordered enzyme synthesis

During outgrowth of spores of Bacillus cereus T, the pattern of enzymes synthesized varied with respect to time. The periods of synthesis of alpha-glucosidase, l-alanine dehydrogenase, and histidase were ordered; each began at a specific time and synthesis continued for only a brief period. An examination of the timing of induced alpha-glucosidase and induced histidase was made to determine whether specific regions of the genome were continually available for transcription and regulation during this period. Several observations indicated that inducers could function during outgrowth, but for only a limited time interval. The period of induced enzyme synthesis occurred over the same interval as that observed for uninduced and catabolically repressed cultures. When inducer was added partway through the period of gene expression, the level of enzyme induction was diminished. Addition of inducer at a time after the period of gene expression had no significant effect. Since messenger ribonucleic acid formed during outgrowth had a half-life of only a few minutes, it was concluded that ordered enzyme synthesis was a result of ordered transcription of the corresponding portion of the genome. An examination of the timing of induced alpha-glucosidase and histidase synthesized in the presence of actinomycin D supported this conclusion.