THE OXIDATION OF THE SULFUR OF HOMOCYSTINE, METHIONINE, AND S-METHYLCYSTEINE IN THE ANIMAL BODY

Abstract

Since it had been found that homocystine could support growth on a cystine-deficient diet in lieu of cystine (l), the oxidative fate of the sulfur of this compound was of interest to us. Furthermore, the possible relationship of this compound to the intermediary metabolism of methionine made such a study desirable. The surprising observation that the feeding of methionine to rats on a cystine-deficient diet results in a marked stimulation of growth was first made by Jackson and Block (2) and has been verified in other laboratories (3, 1). As pointed out by Butz and du Vigneaud (4), one might expect that homocystine would likewise support growth under these conditions if in the metabolism of methionine demethylation took place. The study of the substitution in the diet of methionine and cystine by homocystine was therefore undertaken with the results mentioned above (I), which we feel are in harmony with the idea just expressed in regard to the intermediary metabolism of methionine. It should be recalled that the lack of the growth-promoting powers of other disulfide acids such as @-dithiodipropionic, dithiodiglycolic, and a-dihydroxy-&dithiodipropionic acids has already been shown by Westerman and Rose (5), and therefore the behavior of the disulfide amino acid, homocystine, is all the more significant. The same view-point of the metabolism of methionine on the basis of evidence of an even more direct nature was independently arrived at by Virtue and Lewis (6, 7). These investigators made the interesting observation that after the feeding of methionine to rats and rabbits a positive test for the disulfide linkage was obtained