Some observations on the enzyme, hydrogenase.

Hydrogenase is a member of a small class of enzymes that interact reversibly with diatomic gases (Hz, 02, Nz, CO, and NO). These gases, with the esception of Nt, serve either as substrate or inhibitor of the enzyme, hydrogenase. Our knowledge of the nature of the enzyme is incomplete since it has been derived from studies on bacterial suspensions or partially purified estracts. The isolation of the enzyme in pure form has been hampered because in most organisms it appears to be in particulate form and shows some variation in its properties from one strain of bacteria to another (1). Soluble hydrogenases have been prepared from several organisms. The highest concentration of hydrogenase in whole cells is found in Desuljtibrio cksuljuricans (1,2). Various procedures for purifying the enzyme in this organism have been described by different investigators (1, 3-5). The activities of the purest fractions found by these investigators ranged from &A* of 2.5 X lo6 to 11.4 x lo6 ~1 of Hz activated per mg of N per hour. Other investigators have obtained soluble hydrogenase preparations of similar activity from Clostridium pasteuranium (6) and Clostridium butylicum (7). Our experience with these methods as applied to D. desuljuricans is that none of them is reproducible. Apparently, the enzyme is partly in a soluble form and partly in particulate form. Most methods described will concentrate the soluble form; they fail if the enzyme is in particulate form. We will describe here a method for solubilizing and concentrating the hydrogenase of D. desuljuricans and some properties of the preparations we obtain.