Partial Purification and Characterization of Two Hydrogenases from the Extreme Thermophile Methanococcus jannaschii.
F(420)-nonreactive and F(420)-reactive hydrogenases have been partially purified from Methanococcus jannaschii, an extremely thermophilic methanogen isolated from a submarine hydrothermal vent. The molecular weights of both hydrogenases were determined by native gradient electrophoresis in 5 to 27% polyacrylamide gels. The F(420)-nonreactive hydrogenase produced one major band (475 kilodaltons), whereas the F(420)-reactive hydrogenase produced two major bands (990 and 115 kilodaltons). The F(420)-nonreactive hydrogenase consisted of two subunits (43 and 31 kilodaltons), and the F(420)-reactive hydrogenase contained three subunits (48, 32, and 25 kilodaltons). Each hydrogenase was active at very high temperatures. Methyl viologen-reducing activity of the F(420)-nonreactive hydrogenase was maximal at 80 degrees C but was still detectable at 103 degrees C. The maximum activities of F(420)-reactive hydrogenase for F(420) and methyl viologen were measured at 80 and 90 degrees C, respectively. Low but measureable activity toward methyl viologen was repeatedly observed at 103 degrees C. Moreover, the half-life of the F(420)-nonreactive hydrogenase at 70 degrees C was over 9 h, and that of the F(420)-reactive enzyme was over 3 h.
Shah
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Department of Chemical Engineering, University of California, Berkeley, California 94720.
Clark
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