EFFECT OF ANIONS AND REDOX STATE ON THE ACTIVITY OF MANGANESE CONTAINING CATALASE FROM THERMUS-THERMOPHILUS

Catalase isolated from thermophilic bacterium Thermus thermophilus (Mn-catalase) is composed of six subunits, each containing binuclear manganese clusters at their active site. The enzyme is active when the metal is in the completely reduced (Mn2+Mn2+) state in the pH range 7-10, and loses activity on oxidation. ESR data suggest that the metal turns thereby into the (Mn2+Mn4+) state. The Mn-catalase activity is inhibited by chloride, nitrate, nitrite, azide, and other singly charged anions, except cyanide. The inhibitory effect of anions increases as the pH value is reduced. The inhibition by hydroxylamine takes place through a lag-phase and is weakly dependent on pH value. The reaction mechanism is discussed in relation with current concepts of catalase reactions of heme-proteins and low-molecular binuclear manganese complexes. © 1990.