抄録
Hydrogenase [hydrogen: ferricytochrome c3 oxidoreductase, EC 1. 12. 2. 1] solubilized and purified from the particulate fraction of Desulfovibrio vulgaris Miyazaki F (IAM 12604) contains 8 iron and 8 labile sulfide ions in one molecule which is composed of two unequal subunits (Mr: 60, 000+29, 000). It does not contain nickel atoms. The EPR (electron paramagnetic resonance) spectrum has an isotropic signal at g=2.017 which is independent of the temperature. The peak-to-peak width of the signal is about 20 G. The signal intensity is nearly equivalent to 1 unpaired electron per molecule. No other signals can be detected in the field range between 2, 240 and 4, 240 G (which corresponds to g-values between 2.91 and 1.54). Ferricyanide has only a little effect on the shape and intensity of the EPR signal. The hydrogenase reduced under H2 is EPR silent. The Mössbauer spectrum has no hyperfine splitting at 4 K. The isomer shift and quadrupole splitting at 77 K are 0.38 and 0.87mm/s, respectively. Based on these magnetic measurements, the structure of the active center of hydrogenase was suggested to be [4Fe-4S]3++[4Fe-4S]2+.
