Human erythrocyte glutathione reductase: Chemical mechanism and structure of the transition state for hydride transfer

Journal Article · Tue Sep 03 04:00:00 EDT 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00099a031· OSTI ID:5822232

Sweet, W L; Blanchard, J S ^[1]

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1. Albert Einstein Coll. of Medicine, Bronx, NY (United States)

Kinetic parameters and primary deuterium kinetic isotope effects for NADH and five pyridine nucleotide substrates have been determined at pH 8.1 for human erythrocyte glutathione reductase. The results suggest that as His-467{prime} is deprotonated, the rate of the isotopically insensitive oxidative half-reaction is specifically decreased and becomes rate-limiting. For all substrates, equivalent V and V/K primary deuterium kinetic isotope effects are observed at pH values below 8.1. The primary deuterium kinetic isotope effect on V, but not V/K, is sensitive to solvent isotopic composition. The primary tritium kinetic isotope effects agree well with the corresponding value calculated from the primary deuterium kinetic isotope effects observed in these steady-state experiments are the intrinsic primary deuterium kinetic isotope effect is dependent on the redox potential of the pyridine nucleotide substrate used. Together, these data indicate that the transition state for hydride transfer is very early for NADH and becomes later for thioNADH and 3APADH, as predicted by Hammond's postulate. These data suggest that quantum mechanical tunneling is not significant in the hydride transfer reaction. A chemical mechanism for the reductive half-reaction of human erythrocyte glutathione reductase is proposed on the basis of these data.

• OSTI ID: 5822232
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:35; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
DEUTERIUM COMPOUNDS
DRUGS
ENZYMES
ERYTHROCYTES
GLUTATHIONE
HYDRIDES
HYDROGEN COMPOUNDS
ISOTOPE EFFECTS
KINETICS
MATERIALS
MOLECULAR STRUCTURE
NUCLEOTIDE DEHYDROGENASES
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PEPTIDES
POLYPEPTIDES
PROTEINS
RADIOPROTECTIVE SUBSTANCES
REACTION KINETICS
REDOX POTENTIAL