title: Investigation of alpha-deuterium kinetic isotope effects on the purine nucleoside phosphorylase reaction by the equilibrium-perturbation technique.
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.
authors.affiliation: Department of Organic Chemistry, University of Bristol, U.K.
authors.forename: P K
authors.initials: PK
authors.lastname: Lehikoinen
authors.forename: M L
authors.initials: ML
authors.lastname: Sinnott
authors.forename: T A
authors.initials: TA
authors.lastname: Krenitsky
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D003903:Deuterium / Q000494:pharmacology*; D004926:Escherichia coli; D006863:Hydrogen-Ion Concentration; D007288:Inosine / Q000378:metabolism; D007536:Isomerism; D007554:Isotopes; D007700:Kinetics; D010430:Pentosyltransferases / Q000378:metabolism*; D011683:Purine-Nucleoside Phosphorylase / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D007554:Isotopes; D007288:Inosine; D003903:Deuterium; D010430:Pentosyltransferases; D011683:Purine-Nucleoside Phosphorylase