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


The carbon kinetic isotope effect on the enzymatic dehydration of HCO3- ion is k12/k13 = 1.011 and is independent, within experimental error, of the addition of sucrose, substitution of D2O for H2O, and substitution of enzyme-bound Zn2+ by Co2+. These results are consistent with a ping-pong mechanism in which proton transfer between enzyme and solvent is… (More)


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