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

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

DOI:https://doi.org/10.1021/bi00380a036· OSTI ID:6278082

Paneth, P; O'Leary, M H

The carbon kinetic isotope effect on the enzymatic dehydration of HCO/sub 3/- ion is k12/k13 = 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/- 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-, rather than zinc-bound H/sub 2/O.

• Research Organization: Univ. of Wisconsin, Madison
• OSTI ID: 6278082
• 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 COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBON-OXYGEN LYASES
CARBONIC ANHYDRASE
CATALYSIS
CATTLE
CHALCOGENIDES
COBALT
DEUTERIUM
DOMESTIC ANIMALS
ELEMENTS
ENZYMES
ERYTHROCYTES
HYDRO-LYASES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
HYDROXIDES
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
LYASES
MAMMALS
MATERIALS
METALS
NUCLEI
ODD-ODD NUCLEI
OXIDES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
REACTION KINETICS
RUMINANTS
STABLE ISOTOPES
TRANSITION ELEMENTS
VERTEBRATES
WATER
ZINC