COPPER-CATALYZED AUTOXIDATION OF CYSTEINE. THE AMOUNT OF HYDROGEN PEROXIDE PRODUCED UNDER VARIOUS CONDITIONS AND THE STOICHIOMETRY OF THE REACTION.

Article abstract of DOI:10.1246/bcsj.56.2065

Hydrogen peroxide is shown to be produced as an intermediate from oxygen in the copper-catalyzed autoxidation of cysteine. The amounts of cysteine oxidized and of hydrogen peroxide formed varied depending on the reaction conditions employed. The peroxide upon forming was spontaneously utilized for the oxidation of cysteine. As a result, the ratio of the concentration of hydrogen peroxide formed to cysteine oxidized is variable depending on the conditions. But, in dilute solutions, where the oxidation by the peroxide was slow, a stoichiometric relation of 2:1 was obtained between cysteine consumed and hdyrogen peroxide produced. The rate of autoxidation is dependent on the concentration of oxygen dissolved. The double reciprocal plot of the rate against the concentration of oxygen gives a straight line, which indicates a possibility of the Michaelis-Menten type mechanism concerning the reoxidation or oxygenation of Cu(I) species.