Abstract
The oxidation of cysteine with hydrogen peroxide was performed in a nitrogen atmosphere and in the presence and absence of Cu (II) ion. The reaction was followed spectrophotometrically by measuring the decreases of cysteine and hydrogen peroxide. One molar hydrogen peroxide could oxidize exactly two molar cysteine and this stoichiometric relation was satisfied under any condition examined. As pH was raised, the oxidation was advanced monotonously. Though addition of Cu (II) to oxygen-free cysteine solution containing hydrogen peroxide enhanced the oxidation significantly, cysteine was oxidized at a fairly rapid speed even in the absence of Cu (II) ion. From the observation on the anaerobic oxidation with hydrogen peroxide, as well as on the autoxidation, a probable mechanism for the copper ion-catalyzed autoxidation of cysteine was deduced.
