Kinetic Isotope Effects of Deuterium Oxide on Several α-Chymotrypsin-catalyzed Reactions

1962 ◽  
Vol 84 (13) ◽  
pp. 2570-2576 ◽  
Author(s):  
Myron L. Bender ◽  
Gordon A. Hamilton
Keyword(s):  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Catalyzed Reactions

Evidence for a rate-determining solvation change in methyl transfer to water. Solvent dependence of water-deuterium oxide kinetic isotope effects

1986 ◽  
Vol 108 (11) ◽  
pp. 2960-2968 ◽  
Author(s):  
Joseph L. Kurz ◽  
Jasun. Lee ◽  
Mark E. Love ◽  
Susan. Rhodes
Keyword(s):  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Water Solvent ◽  
Kinetic Isotope ◽  
Methyl Transfer ◽  
Solvent Dependence

scholarly journals Horseradish peroxidase. XXIX. Reactions in water and deuterium oxide: cyanide binding, compound I formation, and reactions of compounds I and II with ferrocyanide

1978 ◽  
Vol 56 (22) ◽  
pp. 2844-2852 ◽  
Author(s):  
H. Brian Dunford ◽  
W. Donald Hewson ◽  
Håkan Steiner
Keyword(s):  
Hydrogen Peroxide ◽  
Horseradish Peroxidase ◽  
Kinetic Isotope Effect ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Compound I ◽  
Kinetic Isotope ◽  
Cyanide Binding ◽  
Compound Ii

The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKa value of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect, kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa 4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid group with a pKa of 5.2 for compound I and for compound II a pKa of 8.6 and another with a value lower than that encompassed by the pH range of the study. Equilibrium isotope effects were found but no kinetic isotope effects for either the reaction of compound I or of compound II This suggests that there are no rate-limiting proton transfers in the reactions between ferrocyanide and compounds I and II of horseradish peroxidase. The only reducing substrates which exhibit positive kH/kD values possess a labile proton.

The expression of kinetic isotope effects during the time course of enzyme-catalyzed reactions

1989 ◽  
Vol 17 (2) ◽  
pp. 177-193 ◽  
Author(s):  
Ronald G. Duggleby ◽  
Dexter B. Northrop
Keyword(s):  
Time Course ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Catalyzed Reactions ◽  
Enzyme Catalyzed Reactions

Kinetic isotope effects and ?metabolic switching? in cytochrome P450-catalyzed reactions

BioEssays ◽  
1987 ◽  
Vol 7 (5) ◽  
pp. 215-219 ◽  
Author(s):  
Gerald T. Miwa ◽  
Anthony Y. H. Lu
Keyword(s):  
Cytochrome P450 ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Metabolic Switching ◽  
Catalyzed Reactions
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