On the catalysis of the oxidation of cysteine and thioglycollic acid by iron and copper

Abstract

The rate of oxidation of cysteine at pH 7.3 is proportional to the amount of Fe present up to a concentration of Fe of 0.05 mgm. per cc. The rate is proportional to the amount of Cu up to a certain concentration, which is not markedly affected by change in temp., O tension, pH, cysteine concentration, or by the presence of phosphate buffer or increased liquid-glass interface. The velocity of oxidation in presence of Fe or Cu is increased by increasing the O tension. Phosphate buffer decreases the velocity of O uptake in the presence of Cu or Fe. Thioglycollic acid in solution at pH 7.3 shows a behavior similar to that of cysteine, except in the following cases: (1) the velocity of O2 uptake in the presence of Fe is very low up to a certain concentration of Fe and thereafter increases rapidly in proportion to the amount of extra Fe added; and (2) higher concentration of thioglycollic acid decreases the rate of O uptake in the presence of Fe.