Leaving-group effects on the ribonuclease T1-catalyzed transphosphorylation of specific substrates

Mitsuhiro Itaya, Yasuo Inoue

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Abstract

A series of alkyl esters of guanosine 3′ -phosphate has been synthesized, and the Michaelis-Menten parameters for the RNase T1- catalyzed transphosphorylation of these substrates have been determined at 25°. Little variation in the parameter Kmi was observed for all substrates; an approximate linear relationship exists between the logarithms of the parameter kcat/Kmi, which is a measure of the rate constant for transphosphorylation of the free RNase T1by free substrate, and the Taft’s substituent constants, s*. A positive p* value obtained and the reactivity sequence arguments taken from the literature indicate an SN2(P) mechanism for RNase T1-transphosphorylation involving direct nucleophilic attack at phosphorus concerted with general acid catalysis of the formation of a pentacovalent intermediate or transition state.

Original languageEnglish
Pages (from-to)s397-s402
JournalNucleic Acids Research
Volume1
DOIs
Publication statusPublished - 1978
Externally publishedYes

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ASJC Scopus subject areas

  • Genetics

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