Investigation of alpha-deuterium kinetic isotope effects on the purine nucleoside phosphorylase reaction by the equilibrium-perturbation technique

Biochem J. 1989 Jan 15;257(2):355-9. doi: 10.1042/bj2570355.

Abstract

1. alpha-Deuterium kinetic isotope effects on the phosphorolysis of inosine catalysed by Escherichia coli purine nucleoside phosphorylase were measured by the equilibrium-perturbation technique, by using the change in absorbance at 250 nm (approx. 20%). 2. Values of 2H(V/K) of 1.13(9) at pH 5.0, 1.10(5) at pH 6.1, 1.09(4) at pH 7.3, 1.08 at pH 8.4 and 1.16(4) at pH 9.4 were obtained. 3. These are compared with literature alpha-deuterium kinetic isotope effects for this and related reactions. 4. The equilibrium constant, defined as [inosine].[H2PO4-]/[hypoxanthine] [alpha-Rib f OPO3H-], is 46 at 25 degrees C. 5. N-3-beta-D-Ribofuranosylhypoxanthine, an impurity in chemically synthesized inosine, is a substrate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chemical Phenomena
  • Chemistry
  • Deuterium / pharmacology*
  • Escherichia coli
  • Hydrogen-Ion Concentration
  • Inosine / metabolism
  • Isomerism
  • Isotopes
  • Kinetics
  • Pentosyltransferases / metabolism*
  • Purine-Nucleoside Phosphorylase / metabolism*
  • Thermodynamics

Substances

  • Isotopes
  • Inosine
  • Deuterium
  • Pentosyltransferases
  • Purine-Nucleoside Phosphorylase