Isotope effect evidence for the zinc hydroxide mechanism of carbonic anhydrase catalyst

Journal Article · Tue Mar 24 04:00:00 EST 1987 · Biochemistry; (United States)

OSTI ID:6220794

Paneth, P; O'Leary, M H

The carbon kinetic isotope effect on the enzymatic dehydration of HCO/sub 3//sup -/ ion is k/sup 12//k/sup 13/ = 1.011 and is independent, within experimental error, of the addition of sucrose, substitution of D/sub 2/O for H/sub 2/O, and substitution of enzyme-bound Zn/sup 2 +/ by Co/sup 2 +/. These results are consistent with a ping-pong mechanism in which proton transfer between enzyme and solvent is separated from HCO/sub 3//sup -/ dehydration. For the dehydration half-reaction, diffusional processes are severalfold faster than dehydration, and the rate-determining step is the dehydration itself. The intrinsic isotope effect is approximately 1.011, indicating that hydration of CO/sub 2/ occurs by reaction of zinc-bound OH/sup -/, rather than zinc-bound H/sub 2/O.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 6220794
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:6; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARBON-OXYGEN LYASES
CARBONIC ANHYDRASE
CATALYSIS
CATTLE
CHEMICAL REACTIONS
DECOMPOSITION
DOMESTIC ANIMALS
ENZYMATIC HYDROLYSIS
ENZYMES
ERYTHROCYTES
EVEN-EVEN NUCLEI
HEAVY WATER
HYDRO-LYASES
HYDROGEN COMPOUNDS
HYDROLYSIS
HYDROXIDES
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
LYASES
LYSIS
MAMMALS
MATERIALS
NUCLEI
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
REACTION KINETICS
RUMINANTS
SOLVOLYSIS
STABLE ISOTOPES
VERTEBRATES
WATER
ZINC COMPOUNDS
ZINC HYDROXIDES