Activation of R235A mutant orotidine 5′-monophosphate decarboxylase by the guanidinium cation

Effective molarity of the cationic side chain of Arg-235

Shonoi A. Barnett, Tina L. Amyes, B. McKay Wood, John Alan Gerlt, John P. Richard

Research output: Contribution to journalArticle

Abstract

The R235A mutation at yeast orotidine 5′-monophosphate decarboxylase (OMPDC) results in a 1300-fold increase in Km and a 14-fold decrease in kcat for decarboxylation of orotidine 5′-monophosphate, corresponding to a 5.8 kcal/mol destabilization of the transition state. There is strong activation of this mutant enzyme by added guanidinium cation (Gua +): 1 M Gua+ stabilizes the transition state by ca. 3 kcal/mol. This stabilization is due to the binding of Gua+ to the binary Emut·OMP complex, with a Kd of 50 mM, to form the 9-fold more reactive ternary Emut·OMP·Gua + complex. The "effectivemolarity" of the cationic side chain of Arg-235 at the wild-type enzyme is calculated to be 160 M.

Original languageEnglish (US)
Pages (from-to)824-826
Number of pages3
JournalBiochemistry
Volume49
Issue number5
DOIs
StatePublished - Feb 9 2010

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Carboxy-Lyases
Guanidine
Cations
Chemical activation
Decarboxylation
Enzyme Activation
Enzymes
Yeast
Stabilization
Yeasts
Mutation
orotidylic acid

ASJC Scopus subject areas

  • Biochemistry

Cite this

Activation of R235A mutant orotidine 5′-monophosphate decarboxylase by the guanidinium cation : Effective molarity of the cationic side chain of Arg-235. / Barnett, Shonoi A.; Amyes, Tina L.; Wood, B. McKay; Gerlt, John Alan; Richard, John P.

In: Biochemistry, Vol. 49, No. 5, 09.02.2010, p. 824-826.

Research output: Contribution to journalArticle

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