Reactions of alloxan and dialuric acid with the sulfhydryl group.

It was the purpose of this investigation to study the reaction between alloxan and the sulfhydryl group of cysteine and compounds containing cysteine. Alloxan injected into animals produced diabetes (1). Cysteine or glutathione injected prior to alloxan, but not after alloxan, protected animals from diabetes (2). On the basis of these data it was postulated that alloxan produced diabetes by the inactivation of essential sulfhydryl enzymes. Since the action of alloxan was not affected by cysteine or glutathione given after the injection of alloxan, it seemed probable that inactivation would involve combination with an essential sulfhydryl group rather than oxidation to the disulfide linkage, since the latter would be a reversible change. Some workers (3,4) believed that the main action of alloxan on sulfhydryl groups was oxidation. Therefore, more data on the reaction of alloxan with cysteine and its derivatives were desirable. Since the compounds involved in this study were unstable, it was thought that the best approach would be to study the changes in the ultraviolet absorption spectrum of alloxan as it was mixed with cysteine and its derivatives.