Trapping of ractive intermediates in enzymology. Exogenous flaviin reduction during catalytic turnover of substrate by gluyoxalase I

Kenneth T. Douglas, A. Joy Quilter, Seiji Shinkai, Kaori Ueda

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Although but weak inhibitors of glyoxalase I under steady-state conditions, flavins are reduced by yeast glyoxalase I (lactoyl-glutathione lyase, EC 4.4.1.5) plus its substrate (the hemithioilacetal from glutathione and phenylglyoxal) during catalytic turnover. Studies with 10-ethylisoalloxazine showed that this flavin reduction was peculiar not merely to glyoxalase I's substrate, but was characteristics of the complete system, enzyme plus substrate undergoing catalytic turnover. Flavins are poor hydride-ion acceptors and the reduction observed most likely represents an oxidative trap of a transient carbanion formed in the glyoxalase I mechanism of action. Hydrophobic flavins were more efficient traps than the hydrophilic ones, and values of the Km for the phenylglyoxal: glutathione hemithiolacetal adduct measured by the flavin-reactions and by normal steady-state-kinetics were closely similar. This argues that trapping has occurred of an enediolate ion (an enzyme-generated carbanion) still bound to glyoxalase I.

Original languageEnglish
Pages (from-to)119-126
Number of pages8
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume829
Issue number1
DOIs
Publication statusPublished - May 20 1985
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology

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