S. K. Shapiro
Dec 1, 1956
Citations
0
Influential Citations
28
Citations
Journal
Journal of Bacteriology
Abstract
Bennett (1941) showed that methylmethionine sulfonium salt [(CH8)2S+CH2CH2CHNH2COOH] supports the growth of rats on a methionine-free diet. Subsequently, it was reported that s-methylmethionine serves as a methyl donor in the biosynthesis of creatine in rat liver slices (Handler and Bernheim, 1943), but not in rat liver homogenates (Cohen, 1953). Recently, McRorie et al. (1954b) isolated smethylmethionine in relatively large amounts from a number of plants. The same group of workers (McRorie et al., 1954a) reported that this compound can replace methionine in a number of microorganisms that require methionine for growth. Inasmuch as the sulfonium derivative of methionine was up to three times as effective as methionine in some cases, it was suggested that s-methylmethionine has some other function in addition to its conversion to methionine. Stekol (1955) described experiments with radioactive compounds which showed that the methyl group of s-methylmethionine was readily available for the synthesis of choline or creatine, but not for the formation of methionine in the rat. When s-methylmethionine was the sole source of sulfur amino acids in the diet, the animals grew poorly compared to rats fed methionine. The discrepancy between the results of Bennett (1941) and those of Stekol (1955) was resolved when it was observed that the rat diet used by Bennett contained cystine in addition to s-methylmethionine. When cystine and s-methylmethionine were fed to rats, Stekol observed growth equal to or better than that obtained on the same diet containing methionine. This led to the same conclusion reached by McRorie et al.: namely, that s-methylmethionine not only serves as a precursor