Investigation of alpha-deuterium kinetic isotope effects on the purine nucleoside phosphorylase reaction by the equilibrium-perturbation technique. |
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| Authors: | P K Lehikoinen M L Sinnott T A Krenitsky |
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| Affiliation: | Department of Organic Chemistry, University of Bristol, U.K. |
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| 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. |
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