THIOL INDUCED HEMOGLOBIN OXIDATION

Addition of cysteine in the mM range to purified oxyhemoglobin, red bl ood cell lysate or red blood cell suspensions leads to oxidation of th e hemoprotein. The rate and extent of the process depend on the initia l hemoglobin and cysteine concentrations, and the reaction is limited by the total destruction of the sulfhydryl groups. Similar results are obtained employing glutathione, but the rate of the process is consid erably slower. Oxidation of the purified hemoprotein is faster than in the red blood cell lysate. This difference is mainly due to the inhib itory effect of catalase present in the lysate. Addition of sodium azi de increases the rate of oxyhemoglobin oxidation in the lysate, while addition of catalase reduces the rate of oxidation of the purified hem oprotein. The results are interpreted in terms of a mechanism comprisi ng the oxidation of the oxyhemoglobin by the -SH group, with concomita nt formation of superoxide anion and hydrogen peroxide. These species further contribute to the oxyhemoglobin oxidation. A chain oxidation o f the thiol, catalyzed by the hemoprotein, explains the extensive cyst eine destruction.