Isotope effect evidence for the zinc hydroxide mechanism of carbonic anhydrase catalysis
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), Vol. 26:6
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBONIC ANHYDRASE
CATALYSIS
HYDROXIDES
BIOCHEMICAL REACTION KINETICS
CARBON DIOXIDE
CATTLE
COBALT
DEUTERIUM
ERYTHROCYTES
ISOTOPE EFFECTS
OXYGEN ISOTOPES
WATER
ZINC
ANIMALS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARBON COMPOUNDS
CARBON OXIDES
CARBON-OXYGEN LYASES
CHALCOGENIDES
DOMESTIC ANIMALS
ELEMENTS
ENZYMES
HYDRO-LYASES
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPES
KINETICS
LIGHT NUCLEI
LYASES
MAMMALS
MATERIALS
METALS
NUCLEI
ODD-ODD NUCLEI
OXIDES
OXYGEN COMPOUNDS
REACTION KINETICS
RUMINANTS
STABLE ISOTOPES
TRANSITION ELEMENTS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques