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

D. M.Z. Schmidt, B. K. Hubbard, J. A. Gerlt

Research output: Contribution to journalArticlepeer-review

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 kcat/KM for L-Ala-D/L-Glu for both proteins are ∼104 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.

Original languageEnglish (US)
Pages (from-to)15707-15715
Number of pages9
JournalBiochemistry
Volume40
Issue number51
DOIs
StatePublished - Dec 25 2001

ASJC Scopus subject areas

  • Biochemistry

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