Solvent exchangeable protons and the activation of molecular oxygen: the galactose oxidase reaction
The reduction of O/sub 2/ to H/sub 2/O/sub 2/ requires two protons as well as two electrons. Thus, activation of dioxygen reasonably may involve either general or specific acid catalysis. Consequently, the reduction of O/sub 2/ to H/sub 2/O/sub 2/ could exhibit a kinetic solvent isotope effect (KSIE). The reaction catalyzed by the mononuclear Cu(II) enzyme, galactose oxidase does exhibit a KSIE (+1.55). The pL-rate profile exhibits an alkaline shift in D/sub 2/O which can be attributed to the differential partitioning of H+ versus D+ between bulk water and a metal-bound H/sub 2/O (delta pKa = +0.19). A variety of spectral evidence places an equatorial, Cu(II)-liganded water molecule at the active site of galactose oxidase. The analysis of the KSIE data is detailed and the potential generality of the function of such metal-bound H/sub 2/O at other type 2 Cu(II) sites is discussed.
- Research Organization:
- State Univ. of New York, Buffalo (USA)
- OSTI ID:
- 6765283
- Journal Information:
- Prog. Clin. Biol. Res.; (United States), Journal Name: Prog. Clin. Biol. Res.; (United States) Vol. 274; ISSN PCBRD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BARYONS
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
CHEMICAL REACTIONS
DEUTERIUM
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
ENZYMES
FERMIONS
HADRONS
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROGEN PEROXIDE
ISOTOPE APPLICATIONS
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LEPTONS
LIGHT NUCLEI
NONMETALS
NUCLEI
NUCLEONS
ODD-ODD NUCLEI
OXIDOREDUCTASES
OXYGEN
OXYGEN COMPOUNDS
PEROXIDES
PROTONS
REACTION KINETICS
REDOX REACTIONS
SOLVENTS
STABLE ISOTOPES
SYNTHESIS
TRACER TECHNIQUES