Product deuterium isotope effect for orotidine 5′-monophosphate decarboxylase: Evidence for the existence of a short-lived carbanion intermediate

Krisztina Toth, Tina L. Amyes, Bryant M. Wood, Kui Chan, John A. Gerlt, John P. Richard

Research output: Contribution to journalArticle

Abstract

A product isotope effect (PIE) of 1.0 was obtained from the ratio of the yields of [6-1H]-uridine 5′-monophosphate (50%) and [6-2H]-uridine 5′-monophosphate (50%) from the decarboxylation of orotidine 5′-monophosphate (OMP) in 50/50 (v/v) H2O/D2O catalyzed by orotidine 5′-monophosphate decarboxylase. This unitary product isotope effect eliminates a proposed mechanism for enzyme-catalyzed decarboxylation in which proton transfer from Lys-93 to C-6 of OMP provides electrophilic push to the loss of CO2 in a concerted reaction. The complete lack of selectivity for the reaction of solvent H and D that is implied by the value of PIE = 1.0 may be enforced by restricted motion of the NL3+ group of the side-chain of Lys-93 that has been proposed to protonate a vinyl carbanion intermediate.

Original languageEnglish (US)
Pages (from-to)12946-12947
Number of pages2
JournalJournal of the American Chemical Society
Volume129
Issue number43
DOIs
StatePublished - Oct 31 2007

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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