Deuterium Fractionation during Molecular Hydrogen Formation in a Marine Pseudomonad

Formic hydrogenlyase, but not foriric dehydrogenase or hydrogenase (hydrogen utilization), was partially inhibited by 33% D/sub 2/O or completely deuterated sodium formate. Thus hypothesis that one, but not two, of the atoms in the evolved hydrogen was in immediate equilibrium with the medium is supported. Mass spectrometric analyses of the hydrogen produced by growing cells showed a deuterium content of about 30 ppm (depleted by a factor of 4.4 to 5.1; theoretical factor = 3.87). The same was true whether glucose or formate was the substrate. The intracellular water and cellular hydrogen were not significantly depleted in deuterium. It is concluded that the fractionation takes place during formate utilization. (auth)