Kinetics of hydrogen isotope exchange reaction catalyzed by Thiocapsa roseopersicina hydrogenase in hydrogen-water system

The kinetics of the hydrogen-water isotope exchange reaction in the H2-HTO, HO-H2O and D2-H2O systems catalyzed by hydrogenase from the purple sulfur bacterium Thiocapsa roseopersicina was studied. The reaction follows the first order kinetics as measured by the isotope technique. The initial rate of the isotope exchange reactions is proportional to the enzyme concentration and is independent of hydrogen concentration. The isotope exchange reaction has a pH maximum. The activation energy is 9+-1 kcal/mol at T=293-323 K. The specific catalytic activity of T. roseopersicina hydrogenase in the hydrogen-water isotope exchange reaction is eqaul to 16+-1 μmol HT x min-1 x mg-1 protein at T=303 K (pH 7.0, PH2=1 atm)