Reaction specificity in pyridoxal phosphate enzymes

Michael D. Toney

Research output: Contribution to journalArticlepeer-review

212 Scopus citations


Pyridoxal phosphate enzymes catalyze a wide variety of reaction types on amines and amino acids, generally by stabilizing carbanionic intermediates. This makes them very useful in cellular metabolism, but it also creates problems in controlling the reaction pathway that a given enzyme follows, i.e., in controlling reaction specificity. Stereoelectronic effects have been proposed to play a major role in determining the bond to Cα that gets broken in the external aldimine intermediate that is common to all PLP enzymes. Here, we discuss our work on dialkylglycine decarboxylase aimed at providing direct evidence for stereoelectronic control of external aldimine reactivity. Once a bond to Cα has been broken to form the carbanionic intermediate, enzymes must also carefully control the fate of this reactive species. Our studies with alanine racemase suggest that the enzyme selectively destabilizes the carbanionic quinonoid intermediate to promote higher racemization specificity by avoiding transamination side reactions.

Original languageEnglish (US)
Pages (from-to)279-287
Number of pages9
JournalArchives of Biochemistry and Biophysics
Issue number1
StatePublished - Jan 1 2005


  • Alanine racemase
  • Dialkylglycine decarboxylase
  • Pyridoxal phosphate
  • Reaction specificity

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Molecular Biology


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