Properties of the cobaltochelatase and the ferrochelatase

The formation of cobaltomesoporphyrin and ferromesoporphyrin in the presence of appropriate, chelatases has been studied. The Km value for mesoporphyrin differs for the two activities, although the optimum pH value is 8.1 for both. At high cobalt concentrations a slight non-enzymatic reaction occurs which is not seen with ferrous salts. Both activities are inhibited by EDTA and by sulphhydryl reagents, whereas disulphide reagents inhibit the cobaltochelatase only.