Purification, characterization, and primary structure of a monofunctional catalase from Methanosarcina barkeri

Methanosarcina barkeri is a strictly anaerobic, cytochrome-containing, meth ane-forming archaeon. We report here that the microorganism contains a cata lase, which was purified and characterized. The enzyme with an apparent mol ecular mass of 190 kDa was shown to be composed of four identical subunits of apparent molecular mass of 54 kDa. The heme-containing enzyme did not ex hibit peroxidase activity, which indicates that it is a monofunctional cata lase. This is substantiated by the primary structure, which is related to t hat of other monofunctional catalases rather than to that of bifunctional c atalase-peroxidases. The enzyme showed an [S](0.5V) for H2O2 of 25 mM and a n apparent V-max of 200,000 U/mg; it was inhibited by azide ([I](0.5V) = 1 mu M) and cyanide ([I](0.5V) = 5 mu M) and inactivated by 1,2,4-aminotriazo le. The activity was almost independent of the pH (between pH 4 and 10) and the temperature (between 15 degrees C and 55 degrees C). Comparison of the primary structure of monofunctional catalases revealed that the enzyme fro m M. barkeri is most closely related to the monofunctional catalase of Dict yostelium discoideum.