PROPERTIES OF CELL-FREE HYDROGENASES OF ESCHERICHIA COLI AND RHODOSPIRILLUM RUBRUM

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Abstract
Cell-free hydrogenases were prepared by various methods and the enzyme partially purified. A survey of properties indi-cated that the enzymes from both sources were essentially similar. Attempts to demonstrate a dissociable cofactor re-quirement for the reduction of methylene blue by H2 gave negative results. Evidence suggesting participation of iron porphyrin enzymes in hydrogenase activity was obtained by visual spectroscopic observations on concentrated solns. of the enzyme from E. coli and on intact cells; these observations disclosed an absorption band at 560 mu which was accentuated by incubation with H2 and discharged by aeration. Factors involved in assay of hydrogenase and in the lability of the enzyme with respect to O2 were studied; oxidation of essential sulfhydryl groups on the enzyme did not appear to explain the inactivation by air. The results were discussed in relation to the mechanisms of various metabolic reactions involving H2.