PMID:11747447
| Citation |
Schmidt, DM, Hubbard, BK and Gerlt, JA (2001) Evolution of enzymatic activities in the enolase superfamily: functional assignment of unknown proteins in Bacillus subtilis and Escherichia coli as L-Ala-D/L-Glu epimerases. Biochemistry 40:15707-15 |
|---|---|
| Abstract |
The members of the mechanistically diverse enolase superfamily catalyze different overall reactions by using a common catalytic strategy and structural scaffold. In the muconate lactonizing enzyme (MLE) subgroup of the superfamily, abstraction of a proton adjacent to a carboxylate group initiates reactions, including cycloisomerization (MLE), dehydration [o-succinylbenzoate synthase (OSBS)], and 1,1-proton transfer (catalyzed by an OSBS that also catalyzes a promiscuous N-acylamino acid racemase reaction). The realization that a member of the MLE subgroup could catalyze a 1,1-proton transfer reaction, albeit poorly, led to a search for other enzymes which might catalyze a 1,1-proton transfer as their physiological reaction. YcjG from Escherichia coli and YkfB from Bacillus subtilis, proteins of previously unknown function, were discovered to be L-Ala-D/L-Glu epimerases, although they also catalyze the epimerization of other dipeptides. The values of k(cat)/K(M) for L-Ala-D/L-Glu for both proteins are approximately 10(4) M(-1) s(-1). The genomic context and the substrate specificity of both YcjG and YkfB suggest roles in the metabolism of the murein peptide, of which L-Ala-D-Glu is a component. Homologues possessing L-Ala-D/L-Glu epimerase activity have been identified in at least two other organisms. |
| Links | |
| Keywords |
Alanine Racemase/chemistry; Alanine Racemase/genetics; Amino Acid Isomerases/chemistry; Amino Acid Isomerases/genetics; Amino Acid Sequence; Aminopeptidases/chemistry; Bacillus subtilis/enzymology; Bacillus subtilis/genetics; Dipeptides/chemistry; Escherichia coli/enzymology; Escherichia coli/genetics; Evolution, Molecular; Genes, Bacterial; Genome, Bacterial; Intramolecular Lyases/chemistry; Intramolecular Lyases/genetics; Kinetics; Molecular Sequence Data; Phosphopyruvate Hydratase/chemistry; Phosphopyruvate Hydratase/genetics; Racemases and Epimerases/chemistry; Racemases and Epimerases/genetics; Sequence Homology, Amino Acid; Serine Endopeptidases/chemistry |
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