Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.1.2.13 (aldolase)
3,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biosynthesis of carnitine proceeds from trimethyllysine (TML) by beta-hydroxylation by a liver or kidney mitochondrial enzyme, which requires oxygen, alpha-ketoglutarate, ferrous iron, and ascorbate. This dioxygenase is rapidly inactivated by preincubation with Fe2+, but not Fe3+. The evidence suggests that superoxide anion is involved in the hydroxylation. beta-Hydroxytrimethyllysine undergoes aldol cleavage to glycine and trimethylaminobutyraldehyde under the influence of serine hydroxymethyltransferase and possibly a specific aldolase. The next step, the aldehyde oxidation, is catalyzed by a specific NAD-dependent aldehyde dehydrogenase from liver cytosol. The product, trimethylaminobutyrate, is then hydroxylated by a cytosolic dioxygenase to carnitine. This enzyme, which has the same cofactor requirements as TML hydroxylase, is found in the liver of all species examined, but is absent from the kidney of some species.
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PMID:Mammalian enzymes of trimethyllysine conversion to trimethylaminobutyrate. 681 45

2-Amino-3-ketobutyrate ligase catalyzes the reversible, pyridoxal 5'-phosphate-dependent condensation of glycine with acetyl CoA forming the unstable intermediate, 2-amino-3-ketobutyrate. Several independent lines of evidence indicate that the pure protein obtained in the purification of this ligase from Escherichia coli also has L-threonine aldolase activity. The evidence includes: (a), a constant ratio of specific activities (aldolase/ligase) at all stages of purifying 2-amino-3-ketobutyrate ligase to homogeneity; (b), the same rate of loss of aldolase and ligase activities during controlled heat inactivation of the pure protein at 60 degrees C in the absence, as well as in the presence of acetyl CoA, a protective substrate; (c), ratios of the two enzymatic activities that are not significantly different during slow inactivation by iodoacetamide, with and without L-threonine added; (d), coincident rates of loss and essentially identical rates of recovery of aldolase activity and ligase activity during resolution of the holoenzyme with hydroxylamine followed by reconstitution with pyridoxal 5'-phosphate. No aldolase activity is observed with D-threonine as substrate and L-allothreonine is about 25% as effective as L-threonine. Whereas ligase activity has a sharp pH optimum at 7.5, the aldolase activity of this pure protein is maximal at pH 9.0. Comparative apparent Km values for glycine (ligase) and L-threonine (aldolase) are 10 mM and 0.9 mM, respectively, whereas corresponding respective Vmax values were found to be 2.5 mumol of CoA released/min per mg vs. 0.014 mumol of acetaldehyde formed (NADH oxidized)/min per mg.
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PMID:Identity and some properties of the L-threonine aldolase activity manifested by pure 2-amino-3-ketobutyrate ligase of Escherichia coli. 834 29

The GLY1 gene of Saccharomyces cerevisiae is required for the biosynthesis of glycine for cell growth [McNeil, J. B., McIntosh, E. V., Taylor, B. V., Zhang, F-R., Tang, S. & Bognar, A. L. (1994) J. Biol. Chem. 269, 9155-9165], but its gene product has not been identified. We have found that the GLY1 protein is similar in primary structure to L-allo-threonine aldolase of Aeromonas jandiae DK-39, which stereospecifically catalyzes the interconversion of L-allo-threonine and glycine. The GLY1 gene was amplified by PCR, with a designed ribosome-binding site, cloned into pUC118, and expressed in Escherichia coli cells. The enzyme was purified to homogeneity, as judged by polyacrylamide gel electrophoresis. The enzyme has a molecular mass of about 170 kDa and consists of four subunits identical in molecular mass. The enzyme contains 2 mol pyridoxal 5'-phosphate/4 mol of subunit as a cofactor, and its absorption spectrum exhibits maxima at 280 nm and 420 nm. The enzyme catalyzes the cleavage of not only L-allo-threonine to glycine but also L-threonine. We have termed the enzyme a low-specific L-threonine aldolase to distinguish it from L-allo-threonine aldolase.
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PMID:The GLY1 gene of Saccharomyces cerevisiae encodes a low-specific L-threonine aldolase that catalyzes cleavage of L-allo-threonine and L-threonine to glycine--expression of the gene in Escherichia coli and purification and characterization of the enzyme. 915 55

L-allo-Threonine aldolase (L-allo-threonine acetaldehyde-lyase), which exhibited specificity for L-allo-threonine but not for L-threonine, was purified from a cell-free extract of Aeromonas jandaei DK-39. The purified enzyme catalyzed the aldol cleavage reaction of L-allo-threonine (K(m) = 1.45 mM, Vmax = 45.2 mumol min-1 mg-1). The activity of the enzyme was inhibited by carbonyl reagents, which suggests that pyridoxal-5'-phosphate participates in the enzymatic reaction. The enzyme does not act on either L-serine or L-threonine, and thus it can be distinguished from serine hydroxy-methyltransferase (L-serine:tetrahydrofolate 5,10-hydroxy-methyltransferase, EC 2.1.2.1) or L-threonine aldolase (EC 4.1.2.5).
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PMID:Purification and characterization of L-allo-threonine aldolase from Aeromonas jandaei DK-39. 922 60

D-Threonine aldolase is an enzyme that catalyzes the cleavage of D-threonine into glycine and acetaldehyde. Its activity was found in several genera of bacteria such as Arthrobacter, Alcaligenes, Xanthomonas, and Pseudomonas, but not in yeasts or fungi. The enzyme was purified to homogeneity from one strain, Arthrobacter sp. DK-38. The enzyme appeared to consist of a single polypeptide chain with an apparent molecular mass of 51 kDa. This enzyme, as well as L-threonine aldolase, requires pyridoxal 5'-phosphate (pyridoxal-P) as a coenzyme. Unlike other pyridoxal-P enzymes, D-threonine aldolase also requires a divalent cation such as Co2+, Ni2+, Mn2+, or Mg2+ for its catalytic activity. The enzyme completely lost its activity in the absence of either pyridoxal-P or a divalent cation. A divalent cation was also essential for the thermal stability of the enzyme. The metal-free enzyme tends to become thermally unstable, resulting in the irreversible loss of its catalytic activity. The enzyme is strictly D-specific for the alpha-position, whereas it cannot distinguish between threo and erythro forms at the beta-position. Thus, D-threonine and D-allothreonine act as substrates of the enzyme, but their kinetic parameters are different; the Km and Vmax values are 3.81 mM and 38.8 micromol x min(-1) x mg(-1) toward D-threonine, and 14.0 mM and 102 micromol x min(-1) x mg(-1) toward D-allothreonine. respectively. The aldolase reaction is reversible, and the enzyme is therefore able to produce nearly equimolar amounts of D-threonine and D-allothreonine through C-C bond formation between glycine and acetaldehyde. The enzyme also acts, in the same manner, on several other D-beta-hydroxy-alpha-amino acids, including D-beta-phenylserine, D-beta-hydroxy-alpha-aminovaleric acid, D-beta-3,4-dihydroxyphenylserine, and D-beta-3,4-methylenedioxyphenylserine.
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PMID:Isolation and characterization of D-threonine aldolase, a pyridoxal-5'-phosphate-dependent enzyme from Arthrobacter sp. DK-38. 934 93

A low-specificity L-threonine aldolase (L-TA) gene from Pseudomonas sp. strain NCIMB 10558 was cloned and sequenced. The gene contains an open reading frame consisting of 1,041 nucleotides corresponding to 346 amino acid residues. The gene was overexpressed in Escherichia coli cells, and the recombinant enzyme was purified and characterized. The enzyme, requiring pyridoxal 5'-phosphate as a coenzyme, is strictly L specific at the alpha position, whereas it cannot distinguish between threo and erythro forms at the beta position. In addition to threonine, the enzyme also acts on various other L-beta-hydroxy-alpha-amino acids, including L-beta-3,4-dihydroxyphenylserine, L-beta-3,4-methylenedioxyphenylserine, and L-beta-phenylserine. The predicted amino acid sequence displayed less than 20% identity with those of low-specificity L-TA from Saccharomyces cerevisiae, L-allo-threonine aldolase from Aeromonas jandaei, and four relevant hypothetical proteins from other microorganisms. However, lysine 207 of low-specificity L-TA from Pseudomonas sp. strain NCIMB 10558 was found to be completely conserved in these proteins. Site-directed mutagenesis experiments showed that substitution of Lys207 with Ala or Arg resulted in a significant loss of enzyme activity, with the corresponding disappearance of the absorption maximum at 420 nm. Thus, Lys207 of the L-TA probably functions as an essential catalytic residue, forming an internal Schiff base with the pyridoxal 5'-phosphate of the enzyme to catalyze the reversible aldol reaction.
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PMID:Gene cloning, nucleotide sequencing, and purification and characterization of the low-specificity L-threonine aldolase from Pseudomonas sp. strain NCIMB 10558. 946 92

Enzymes proceed the reaction with high regio- and stereoselectivity under mild conditions, i.e. in an aqueous medium at room temperature. However, enzymatic reactions that catalyze carbon-carbon bond formation have not been utilized in organic synthesis until recently. We had an interest in an aldolase-catalyzed reaction which proceed carbon-carbon bond formation referred to aldol condensation, by which many bioactive compounds have been rationally synthesized. On the other hand, recent biological studies on cell recognition (cell adhesion) have disclosed the important roles of oligosaccharides on cell surfaces, especially which include glucuronic acid, 3-deoxy-D-manno-oct-2-ulosonic acid (KDO), and sialic acid in the structures e.g., sialyl Lewis X and endotoxins, in differentiation, induction, viral and bacterial infections, and immune response. As well as acidic oligosaccharides, basic ones have been utilized as practical medicines in the clinical level, like acarbose that acts as an amylase inhibitor. Based on these background, we embarked the synthesis of carbohydrate related compounds which can control the interaction between carbohydrates and carbohydrate recognition protein by the use of several aldolases. Azasugars, potent inhibitors toward glycosidases, were synthesized using fructose-1,6-diphosphate (FDP)-aldolase and other dihdroxyacetonephosphate (DHAP)-dependent aldolases in the key step. Sialyl Lewis X mimetic, peptidic mimetic of RNA having anti-Vero toxin activity, mycestericin D, and aza-idulonic acid were prepared by taking advantage of L-threonine aldolase catalyzed reaction, which afford beta-hydroxy-alpha-L-amino acids. A precursor of KDO, featured acidic sugar of endotoxins was provided by the reaction catalyzed with kynureninase, which generates beta-anion of L-alanine in its active site during the metabolic reaction from kynurenine to anthranilic acid.
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PMID:[Synthesis of carbohydrate related compounds by using aldolase catalyzed reaction]. 1065 81

Vitamin B(6)-dependent enzymes may be grouped into five evolutionarily unrelated families, each having a different fold. Within fold type I enzymes, L-threonine aldolase (L-TA) and fungal alanine racemase (AlaRac) belong to a subgroup of structurally and mechanistically closely related proteins, which specialised during evolution to perform different functions. In a previous study, a comparison of the catalytic properties and active site structures of these enzymes suggested that they have a catalytic apparatus with the same basic features. Recently, recombinant D-threonine aldolases (D-TAs) from two bacterial organisms have been characterised, their predicted amino acid sequences showing no significant similarities to any of the known B(6) enzymes. In the present work, a comparative structural analysis suggests that D-TA has an alpha/beta barrel fold and therefore is a fold type III B(6) enzyme, as eukaryotic ornithine decarboxylase (ODC) and bacterial AlaRac. The presence of both TA and AlaRac in two distinct evolutionary unrelated families represents a novel and interesting example of convergent evolution. The independent emergence of the same catalytic properties in families characterised by completely different folds may have not been determined by chance, but by the similar structural features required to catalyse pyridoxal phosphate-dependent aldolase and racemase reactions.
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PMID:Threonine aldolase and alanine racemase: novel examples of convergent evolution in the superfamily of vitamin B6-dependent enzymes. 1268 35

The glyA gene encoding a serine hydroxymethyl transferase (SHMT) with threonine aldolase activity was isolated from Streptococcus thermophilus YKA-184 chromosomal DNA. This aldolase is a pyridoxal 5'-phosphate-dependent enzyme that stereospecifically catalyzes the interconversion of L-threonine to glycine and acetaldehyde. The enzyme was overexpressed in Escherichia coli M15 as a recombinant protein of 45 kDa with a His6-tag at its N-terminus. The recombinant enzyme was purified to homogeneity by a single chromatographic step using Ni-nitrilotriacetic acid affinity, obtaining a high activity-recovery yield (83%). Lyophilized and precipitated enzymes were stable at least for 10 weeks when stored at -20 degrees C and 4 degrees C. It was observed that the Km for L-allo-threonine was 38-fold higher than that for L-threonine, suggesting this enzyme can be classified as a specific L-allo-threonine aldolase. The optimum pH range of threonine aldolase activity for the recombinant SHMT was pH 6-7. When tested for aldol addition reactions with non-natural aldehydes, such as benzyloxyacetaldehyde and (R)-N-Cbz-alaninal, two possible beta-hydroxy-alpha-amino acid diastereoisomers were produced, but with moderate stereospecificity. The enzyme showed potential as a biocatalyst for the stereoselective synthesis of beta-hydroxy-alpha-amino acids.
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PMID:Recombinant production of serine hydroxymethyl transferase from Streptococcus thermophilus and its preliminary evaluation as a biocatalyst. 1572 49

Carnitine is an essential metabolite that enables intracellular transport of fatty acids and acetyl units. Here we show that the yeast Candida albicans can synthesize carnitine de novo, and we identify the 4 genes of the pathway. Null mutants of orf19.4316 (trimethyllysine dioxygenase), orf19.6306 (trimethylaminobutyraldehyde dehydrogenase), and orf19.7131 (butyrobetaine dioxygenase) lacked their respective enzymatic activities and were unable to utilize fatty acids, acetate, or ethanol as a sole carbon source, in accordance with the strict requirement for carnitine-mediated transport under these growth conditions. The second enzyme of carnitine biosynthesis, hydroxytrimethyllysine aldolase, is encoded by orf19.6305, a member of the threonine aldolase (TA) family in C. albicans. A strain lacking orf19.6305 showed strongly reduced growth on fatty acids and was unable to utilize either acetate or ethanol, but TA activity was unaffected. Growth of the null mutants on nonfermentable carbon sources is restored only by carnitine biosynthesis intermediates after the predicted enzymatic block in the pathway, which provides independent evidence for a specific defect in carnitine biosynthesis for each of the mutants. In conclusion, we have genetically characterized a complete carnitine biosynthesis pathway in C. albicans and show that a TA family member is mainly involved in the aldolytic cleavage of hydroxytrimethyllysine in vivo.
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PMID:Identification and characterization of a complete carnitine biosynthesis pathway in Candida albicans. 1928 5


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