Cystamine disulfoxide

Tests to determine the nature of the compounds formed from the decarboxylation of cystine that could undergo oxidation led to the observation that cystamine disulfoxide was oxidized with ease, whereas cystamine was completely resistant. From these observations, it was hypothesized that two oxidizing enzymes may be involved in the reaction, one oxidizing cystine to the disulfoxide, and one continuing the oxidation of the cystamine disulfoxide subsequent to the decarboxylation of the cystine disulfoxide. If it is assumed that the cystamine disulfoxide is simultaneously oxidized and cleaved to 2-aminoethanesulfinic acid, the oxidation scheme leads to the intermediate that was established for the biosynthesis of taurine from cysteine by Awapara. ... 

An alternate possibility is a direct oxidation of cysteine to sulfenic and sulfinic acid (16), Eq. (3). Medes and Floyd (17) observed that a particulate preparation of liver homogenate catalyzes the production of CO from cystine and it was suggested that cystine may be oxidized to the disulfoxide which is then decarboxylated to cystamine disulfoxide Eq. (4). The latter could be converted to hypotaurine and then to taurine. The sequence of these hypothetical reactions is as follows ... 

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