pH Dependence and solvent deuterium oxide kinetic isotope effects on Bacillus cereus .beta.-lactamase I catalyzed reactions

Biochemistry ◽  
1984 ◽  
Vol 23 (6) ◽  
pp. 1282-1287 ◽  
Author(s):  
Larry W. Hardy ◽  
J. F. Kirsch
Keyword(s):  
Bacillus Cereus ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Ph Dependence ◽  
Kinetic Isotope Effects ◽  
Beta Lactamase ◽  
Kinetic Isotope ◽  
Catalyzed Reactions

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

Horseradish Peroxidase. XVII. Reactions of Compounds I and II with p-Aminobenzoic Acid in Deuterium Oxide

1975 ◽  
Vol 53 (11) ◽  
pp. 1563-1569 ◽  
Author(s):  
C. D. Hubbard ◽  
H. B. Dunford ◽  
W. D. Hewson
Keyword(s):  
Horseradish Peroxidase ◽  
Dissociation Constants ◽  
Deuterium Oxide ◽  
Isotope Effects ◽  
Ph Dependence ◽  
Order Rate Constant ◽  
Enzyme Concentration ◽  
Acid Dissociation ◽  
Aminobenzoic Acid ◽  
Kinetic Isotope

The kinetics of reactions of horseradish peroxidase compounds I and II (HRP-I and HRP-II, respectively) with p-aminobenzoic acid have been studied in ordinary water and in deuterium oxide solution over a pH (pD) range 3–10, at 25° and at an ionic strength of 0.11. Under the conditions of the experiments the rate of reaction is first order both in substrate concentration and in enzyme concentration in both solvents. An analysis of the pH dependence of the second order rate constant in H2O confirms the presence of two acid dissociation groups on the enzyme with pKa' of 8.6 and ∼0 for HRP-II, whereas for HRP-I the data suggest a pKa of 5.1 on the enzyme and reveal, as previously shown, the influence of the ionization of the substituted ammonium group of the substrate. In deuterium oxide the pD profiles are similar to those in water but significant shifts for both kinetic and acid dissociation constants are observed for both compounds.The numerical values of the isotope effects taken together with previous results in general confirm that with labile substrates the group of pKa 8.6 in H2O on HRP-II is involved in general acid catalysis. p-Aminobenzoic acid is intermediate between labile and somewhat unreactive substrates and behaves similarly to the ferrocyanide ion in that both acid dissociation groups (pKa's 8.6 and ∼0) are influential in the catalysis of substrate oxidation by HRP-II. The kinetic isotope effect for the HRP-I reaction with p-aminobenzoic acid at high pH (pD) is consistent with a rate determining proton transfer but the group of pKa 5.1 in H2O remains unidentified.

The pH dependence of xanthine oxidase catalysis in basic solution

1980 ◽  
Vol 58 (5) ◽  
pp. 394-398 ◽  
Author(s):  
John W. Bunting ◽  
Keith R. Laderoute ◽  
Donald J. Norris
Keyword(s):  
Xanthine Oxidase ◽  
Isotope Effects ◽  
Ph Dependence ◽  
Kinetic Isotope Effects ◽  
Similar Rate ◽  
Basic Solution ◽  
Kinetic Isotope ◽  
Steady State Kinetics ◽  
Pyridinium Cations ◽  
Kinetics Of

The steady-state kinetics of the oxidation of the following six heteroaromatic substrates by xanthine oxidase have been investigated over the range pH 9.0–11.1 at 25 °C, ionic strength 0.1: 1-methylquinolinium, 6-methoxy-1-methylquinolinium, 1-methylnicotinamide, 3-acetyl-1-methylpyridinium, and 1-(4-methoxyphenyl)pyridinium cations and 1-methylnicotinate zwitterion. For the first four of these species, kc and Km were evaluated as a function of pH while only kc/Km was accessible in the latter two cases. Where available, kc is pH independent, whereas plots of log (kc/Km) vs. pH are linear with slopes in the range 0.54–1.17.The rates of enzymic oxidation of the 1-methylquinolinium cation and its 2-deuterio derivative were investigated and kinetic isotope effects were calculated at pH 9.8 and 10.6: kcH/kcD = 1.7 and KmH/KmD = 0.4 at each pH. Detailed comparisons of the oxidation of heteroaromatic cations and xanthine-derived substrates indicate that similar rate-determining steps control the enzymic oxidations of these two classes of substrate.

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

Reactions of Muonium with simple biochemical solutes in water and micelles

1991 ◽  
Vol 69 (8) ◽  
pp. 1252-1258 ◽  
Author(s):  
Mary V. Barnabas ◽  
David C. Walker
Keyword(s):  
Reaction Mechanism ◽  
Organic Compounds ◽  
Rate Constants ◽  
Enhancement Factor ◽  
Isotope Effects ◽  
Ph Dependence ◽  
Kinetic Isotope Effects ◽  
Natural State ◽  
Sugar Phosphate ◽  
Kinetic Isotope

Rate constants are reported for the reaction of muonium atoms in water with some 36 organic compounds, many of interest in biology. These kM values range from < l05 to 7 × 1010 M−1 s−1, according to the type of reaction involved, with the sugar–phosphate backbones of nucleic acids being at the low end and their bases at the high end. They are compared with corresponding published H-atom data (kH), where possible, and show kinetic-isotope-effects ranging over five orders of magnitude. Since all kH data were obtained at pH = 1, while kM values refer to pH ~ 7 of the natural state, the pH-dependence of kM was examined in representative cases. The changes found result from protonation of the solute rather than a changed reactivity of Mu on being converted to MuH+. On localizing the solutes in the hydrophobic phase of dilute micelles, the reactivity of Mu was again measured (kM(mic)). The resulting "enhancement" factor was considered in terms of: the reaction mechanism, its dependence on microenvironment (solvation), and the concentrating effect of mutual confinement to small sections of a biphasal system. Key words: kinetic isotope effects, muonium, biochemicals, micelles.

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.

Mycobacterium tuberculosisMycothione Reductase:  pH Dependence of the Kinetic Parameters and Kinetic Isotope Effects†

Biochemistry ◽  
2001 ◽  
Vol 40 (17) ◽  
pp. 5119-5126 ◽  
Author(s):  
Mehul P. Patel ◽  
John S. Blanchard
Keyword(s):  
Kinetic Parameters ◽  
Isotope Effects ◽  
Ph Dependence ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope
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