REVERSIBLE HYDROGENASE OF ANABAENA-VARIABILIS ATCC-29413 - CATALYTIC PROPERTIES AND CHARACTERIZATION OF REDOX CENTERS

The catalytic and spectroscopic properties of the reversible hydrogena se from the cyanobacterium Anabaena variabilis have been examined. The hydrogenase required reductive activation in order to elicit hydrogen -oxidation activity. Carbon monoxide was a weak (K-i = 35 mu M), rever sible and competitive inhibitor. A flavin with the chromatographic pro perties of FMN, and nickel were detected in the purified enzyme. A. va riabilis hydrogenase exhibited electron paramagnetic resonance (EPR) s pectra in its hydrogen-reduced state, indicative of [2Fe-2S] and [4Fe- 4S] clusters. Although no EPR signals due to nickel were detected, the results are consistent with the enzyme being a flavin-containing hydr ogenase of the nickel-iron type.