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Yeast glutathione reductase. Studies of the kinetics and stability of the enzyme as a function of pH and salt concentration.
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JournalBiochim. Biophys. ActaNot FoundDate
1975-Nov-20
Publication Type
Research Support, U.S. Gov't, P.H.S.
Journal Article
Volume
1975-Nov-20 / 410 : 21-31
Author
Moroff G , Brandt KG
DoiPMIDMESH
Acetates
Drug Stability
Enzyme Activation
Glutathione
Glutathione Reductase
Hydrogen-Ion Concentration
Kinetics
Osmolar Concentration
Oxidation-Reduction
Saccharomyces cerevisiae
Temperature
Abstract
1. The pH dependencies of the apparent Michaelis constant for oxidized glutathione and the apparent turnover number of yeast glutathione reductase (EC 1.6.4.2) have been determined at a fixed concentration of 0.1 mM NADPH in the range pH 4.5--8.0. Between pH 5.5 and 7.6, both of these parameters are relatively constant. The principal effect of low pH on the kinetics of the enzyme-catalyzed reaction is the observation of a pH-dependent substrate inhibition by oxidized glutathione at pH less than or equal 7, which is shown to correlate with the binding of oxidized glutathione to the oxidized form of the enzyme. 2. The catalytic activity of yeast glutathione reductase at pH 5.5 is affected by the sodium acetate buffer concentration. The stability of the oxidized and reduced forms of the enzyme at pH 5.5 and 25 degrees C in the absence of bovine serum albumin was studied as a function of sodium acetate concentration. The results show that activation of the catalytic activity of the enzyme at low sodium acetate concentration correlates with an effect of sodium acetate on a reduced form of the enzyme. In contrast, inhibition of the catalytic activity of the enzyme at high sodium acetate concentration correlates with an effect of sodium acetate on the oxidized form of the enzyme.
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Biochim. Biophys. ActaBiochimica et biophysica acta
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