Effects of cysteine on the inactivation of bovine liver catalase
Bovine liver catalase was exposed to cysteine, as a natural inactivator metabolite, causing autoxidation-generating H(2)O(2) continuously. The catalase species concentrations and activity measurement were done by spectrophotometry in phosphate buffer 10 mM, pH 6.5, and 27 degrees C. The activity of catalase decreased continuously due to the conversion of active ferricatalase species, E-Fe (III), to an inactive enzyme species, E-Fe (IV). This conversion is related to the slow production of H(2)O(2) generated by autoxidation of cysteine. The free SH-group of cysteine has an essential role in production of H(2)O(2) and hence inactivation of catalase. NADPH can protect catalase against inactivation due to the conversion of inactive form of E-Fe (IV) to ferricatalase species, E-Fe (III).