Steady-state kinetic studies of the inhibitory action of Zn2+ on ribonuclease T1 catalysis.

M. Itaya, Y. Inoue

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Abstract

The kinetic mechanism of specific inhibition by Zn2+ of ribonuclease T1 catalysis was studied by steady-state kinetic analysis of transphosphorylation of dinucleotides, GpCp(3'), GpUp(2') and GpUp(3'), and dinucleoside monophosphates, GpC and GpU. The inhibition was not simply competitive, non-competitive or uncompetitive, but the kinetic data were compatible with a mechanism of 'fully mixed inhibition' in which a fully non-competitive action was associated with a partially competitive action. Apparent equilibrium quotients involved in this model of inhibition were determined for the dinucleotide substrates, and we found that binding of either of Zn2+ and substrate was facilitated when the other was bound. The location of Zn2+ was suggested to be near His-40 and/or His-92 of the ribonuclease T1 molecule.

Original languageEnglish
Pages (from-to)357-362
Number of pages6
JournalThe Biochemical journal
Volume207
Issue number2
DOIs
Publication statusPublished - 1982 Nov 1

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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