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

---

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

1. Two strains of Pseudomonas were grown with phenol and used to prepare cell extracts that metabolized catechol with the transient formation of 2-hydroxymuconic semialdehyde. 2. One of these preparations catalysed the conversion of 1mol. of catechol into 1mol. each of formate and 4-hydroxy-2-oxovalerate. 3. A method for the determination of 4-hydroxy-2-oxovalerate is described, together with some properties of this compound and its 2,4-dinitrophenylhydrazone. 4. Another partially purified cell extract converted 1mol. of 4-hydroxy-2-oxovalerate, formed enzymically from catechol, into 1mol. each of acetaldehyde and pyruvate. This aldolase had a pH optimum of about 8.8, was stimulated by Mg(2+) ions and appeared to attack only one enantiomer of synthetic 4-hydroxy-2-oxovalerate.
...
PMID:THE BACTERIAL DEGRADATION OF CATECHOL. 1434 96

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.
...
PMID:Recombinant production of serine hydroxymethyl transferase from Streptococcus thermophilus and its preliminary evaluation as a biocatalyst. 1572 49

Aldolases are a specific group of lyases that catalyze the reversible stereoselective addition of a donor compound (nucleophile) onto an acceptor compound (electrophile). Whereas most aldolases are specific for their donor compound in the aldolization reaction, they often tolerate a wide range of aldehydes as acceptor compounds. C-C bonding by aldolases creates stereocenters in the resulting aldol products. This makes aldolases interesting tools for asymmetric syntheses of rare sugars or sugar-derived compounds as iminocyclitols, statins, epothilones, and sialic acids. Besides the well-known fructose 1,6-bisphosphate aldolase, other aldolases of microbial origin have attracted the interest of synthetic bio-organic chemists in recent years. These are either other dihydroxyacetone phosphate aldolases or aldolases depending on pyruvate/phosphoenolpyruvate, glycine, or acetaldehyde as donor substrate. Recently, an aldolase that accepts dihydroxyacetone or hydroxyacetone as a donor was described. A further enlargement of the arsenal of available chemoenzymatic tools can be achieved through screening for novel aldolase activities and directed evolution of existing aldolases to alter their substrate- or stereospecifities. We give an update of work on aldolases, with an emphasis on microbial aldolases.
...
PMID:Microbial aldolases as C-C bonding enzymes--unknown treasures and new developments. 1661 60

Aldolases are emerging as powerful and cost efficient tools for the industrial synthesis of chiral molecules. They catalyze enantioselective carbon-carbon bond formations, generating up to two chiral centers under mild reaction conditions. Despite their versatility, narrow substrate ranges and enzyme inactivation under synthesis conditions represented major obstacles for large-scale applications of aldolases. In this study we applied directed evolution to optimize Escherichia coli 2-deoxy-D-ribose 5-phosphate aldolase (DERA) as biocatalyst for the industrial synthesis of (3R,5S)-6-chloro-2,4,6-trideoxyhexapyranoside. This versatile chiral precursor for vastatin drugs like Lipitor (atorvastatin) is synthesized by DERA in a tandem-aldol reaction from chloroacetaldehyde and two acetaldehyde equivalents. However, E. coli DERA shows low affinity to chloroacetaldehyde and is rapidly inactivated at aldehyde concentrations useful for biocatalysis. Using high-throughput screenings for chloroacetaldehyde resistance and for higher productivity, several improved variants have been identified. By combination of the most beneficial mutations we obtained a tenfold improved variant compared to wild-type DERA with regard to (3R,5S)-6-chloro-2,4,6-trideoxyhexapyranoside synthesis, under industrially relevant conditions.
...
PMID:Directed evolution of an industrial biocatalyst: 2-deoxy-D-ribose 5-phosphate aldolase. 1689 89

Amino acids are not only fundamental protein constituents but also serve as precursors for many essential plant metabolites. Although amino acid biosynthetic pathways in plants have been identified, pathway regulation, catabolism, and downstream metabolite partitioning remain relatively uninvestigated. Conversion of Thr to Gly and acetaldehyde by Thr aldolase (EC 4.1.2.5) was only recently shown to play a role in plant amino acid metabolism. Whereas one Arabidopsis thaliana Thr aldolase (THA1) is expressed primarily in seeds and seedlings, the other (THA2) is expressed in vascular tissue throughout the plant. Metabolite profiling of tha1 mutants identified a >50-fold increase in the seed Thr content, a 50% decrease in seedling Gly content, and few other significant metabolic changes. By contrast, homozygous tha2 mutations cause a lethal albino phenotype. Rescue of tha2 mutants and tha1 tha2 double mutants by overproduction of feedback-insensitive Thr deaminase (OMR1) shows that Gly formation by THA1 and THA2 is not essential in Arabidopsis. Seed-specific expression of feedback-insensitive Thr deaminase in both tha1 and tha2 Thr aldolase mutants greatly increases seed Ile content, suggesting that these two Thr catabolic enzymes compete for a common substrate pool.
...
PMID:Two Arabidopsis threonine aldolases are nonredundant and compete with threonine deaminase for a common substrate pool. 1717 52

A two-step enzymatic synthesis process of 4-hydroxyisoleucine is suggested. In the first step, the aldol condensation of acetaldehyde and alpha-ketobutyrate catalyzed by specific aldolase results in the formation of 4-hydroxy-3-methyl-2-keto-pentanoate (HMKP). In the second step, amination of HMKP by the branched-chain amino acid aminotransferase leads to synthesis of 4-hydroxyisoleucine. An enzyme possessing HMKP aldolase activity (asHPAL) was purified 2500-fold from a crude extract of Arthrobacter simplex strain AKU 626. Sequencing of the asHPAL structural gene showed that the purified enzyme belongs to the HpcH/HpaI aldolase family. The 4-hydroxyisoleucine was synthesized in vitro from acetaldehyde, alpha-ketobutyrate and l-glutamate using a coupled aldolase/branched-chain amino acid aminotransferase bienzymatic reaction.
...
PMID:A novel strategy for enzymatic synthesis of 4-hydroxyisoleucine: identification of an enzyme possessing HMKP (4-hydroxy-3-methyl-2-keto-pentanoate) aldolase activity. 1755 90

The growth of Pyrobaculum aerophilum on yeast extract and nitrate was stimulated by the addition of maltose. Extracts of maltose/yeast extract/nitrate-grown cells contained all enzyme activities of a modified Embden-Meyerhof (EM) pathway, including ATP-dependent glucokinase, phosphoglucose isomerase, ATP-dependent 6-phosphofructokinase, fructose-1,6-phosphate aldolase, triose-phosphate isomerase, GAPOR, phosphoglycerate mutase, enolase and pyruvate kinase. The activity of GAPOR was stimulated about fourfold by maltose, indicating a role in sugar degradation. GAPOR was purified 200-fold to homogeneity and characterized as a 67 kDa monomeric, extremely thermostable protein. The enzyme showed high specificity for glyceraldehyde-3-phosphate and did not use glyceraldehyde, acetaldehyde or formaldehyde as substrates. By matrix-assisted laser desorption/ionization-time of flight analysis of the purified enzyme, ORF PA1029 was identified as a coding gene, gapor, in the sequenced genome of Pyrobaculum aerophilum. The data indicate that the (micro)aerophilic Pyrobaculum aerophilum contains a functional GAPOR as part of a modified EM pathway. Cells of the strictly aerobic crenarchaeon Aeropyrum pernix also contain enzyme activities of a modified EM pathway similar to that of Pyrobaculum aerophilum, except that a GAPN activity replaces GAPOR activity.
...
PMID:Glyceraldehyde-3-phosphate ferredoxin oxidoreductase (GAPOR) and nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN), key enzymes of the respective modified Embden-Meyerhof pathways in the hyperthermophilic crenarchaeota Pyrobaculum aerophilum and Aeropyrum pernix. 1755 73

Arthrobacter simplex AKU 626 was found to synthesize 4-hydroxyisoleucine from acetaldehyde, alpha-ketobutyrate, and L-glutamate in the presence of Escherichia coli harboring the branched chain amino acid transaminase gene (ilvE) from E. coli K12 substrain MG1655. By using resting cells of A. simplex AKU 626 and E. coli BL21(DE3)/pET-15b-ilvE, 3.2 mM 4-hydroxyisoleucine was produced from 250 mM acetaldehyde, 75 mM alpha-ketobutyrate, and 100 mM L-glutamate with a molar yield to alpha-ketobutyrate of 4.3% in 50 mM Tris-HCl buffer (pH 7.5) containing 2 mM MnCl(2) x 4H(2)O at 28 degrees C for 2 h. An aldolase that catalyzes the aldol condensation of acetaldehyde and alpha-ketobutyrate was purified from A. simplex AKU 626. Mn(2+) and pyridoxal 5'-monophosphate were effective in stabilizing the enzyme. The native and subunit molecular masses of the purified aldolase were about 180 and 32 kDa respectively. The N-terminal amino acid sequence of the purified enzyme showed no significant homology to known aldolases.
...
PMID:Synthesis of 4-hydroxyisoleucine by the aldolase-transaminase coupling reaction and basic characterization of the aldolase from Arthrobacter simplex AKU 626. 1761 27

Genes encoding 2-deoxy-d-ribose-5-phosphate aldolase (DERA) homologues from two hyperthermophiles, the archaeon Pyrobaculum aerophilum and the bacterium Thermotoga maritima, were expressed individually in Escherichia coli, after which the structures and activities of the enzymes produced were characterized and compared with those of E. coli DERA. To our surprise, the two hyperthermophilic DERAs showed much greater catalysis of sequential aldol condensation using three acetaldehydes as substrates than the E. coli enzyme, even at a low temperature (25 degrees C), although both enzymes showed much less 2-deoxy-d-ribose-5-phosphate synthetic activity. Both the enzymes were highly resistant to high concentrations of acetaldehyde and retained about 50% of their initial activities after a 20-h exposure to 300 mM acetaldehyde at 25 degrees C, whereas the E. coli DERA was almost completely inactivated after a 2-h exposure under the same conditions. The structure of the P. aerophilum DERA was determined by X-ray crystallography to a resolution of 2.0 A. The main chain coordinate of the P. aerophilum enzyme monomer was quite similar to those of the T. maritima and E. coli enzymes, whose crystal structures have already been solved. However, the quaternary structure of the hyperthermophilic enzymes was totally different from that of the E. coli DERA. The areas of the subunit-subunit interface in the dimer of the hyperthermophilic enzymes are much larger than that of the E. coli enzyme. This promotes the formation of the unique dimeric structure and strengthens the hydrophobic intersubunit interactions. These structural features are considered responsible for the extremely high stability of the hyperthermophilic DERAs.
...
PMID:Sequential aldol condensation catalyzed by hyperthermophilic 2-deoxy-d-ribose-5-phosphate aldolase. 1790 78

The meta-cleavage pathway for catechol is a central pathway for the bacterial dissimilation of a wide variety of aromatic compounds, including phenols, methylphenols, naphthalenes, and biphenyls. The last enzyme of the pathway is a bifunctional aldolase/dehydrogenase that converts 4-hydroxy-2-ketovalerate to pyruvate and acetyl-CoA via acetaldehyde. The structure of the NAD (+)/CoASH-dependent aldehyde dehydrogenase subunit is similar to that of glyceraldehyde-3-phosphate dehydrogenase, with a Rossmann fold-based NAD (+) binding site observed in the NAD (+)-enzyme complex [Manjasetty, B. A., et al. (2003) Proc. Natl. Acad. Sci. U.S.A. 100, 6992-6997]. However, the location of the CoASH binding site was not determined. In this study, hydrogen-deuterium exchange experiments, coupled with peptic digest and mass spectrometry, were used to examine cofactor binding. The pattern of hydrogen-deuterium exchange in the presence of CoASH was almost identical to that observed with NAD (+), consistent with the two cofactors sharing a binding site. This is further supported by the observations that either CoASH or NAD (+) is able to elute the enzyme from an NAD (+) affinity column and that preincubation of the enzyme with NAD (+) protects against inactivation by CoASH. Consistent with these data, models of the CoASH complex generated using AUTODOCK showed that the docked conformation of CoASH can fully occupy the cavity containing the enzyme active site, superimposing with the NAD (+) cofactor observed in the X-ray crystal structure. Although CoASH binding Rossmann folds have been described previously, this is the first reported example of a Rossmann fold that can alternately bind CoASH or NAD (+) cofactors required for enzymatic catalysis.
...
PMID:A shared binding site for NAD+ and coenzyme A in an acetaldehyde dehydrogenase involved in bacterial degradation of aromatic compounds. 1853 68


<< Previous 1 2 3 4 5 6 7 Next >>

---