The Journal of Biochemistry
Online ISSN : 1756-2651
Print ISSN : 0021-924X
Enzymatic Studies on the Metabolism of the Tetrahydrofurfuryl Mercaptan Moiety of Thiamine Tetrahydrofurfuryl Disulfide
I. Microsomal S-Transmethylase
Takeshi FUJITAZiro SUZUOKI
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1973 Volume 74 Issue 4 Pages 717-722

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Abstract

Enzyme systems responsible for the novel metabolic pathway of foreign mercaptans leading to the formation of methylsulfonyl metabolites were investigated in rat tissues. The first step was shown to be S-transmethylation. Tetrahydrofurfuryl mercaptan was methylated to its methyl sulfide by liver homogenates in the presence of S-adenosylmethionine. The activity was highest in liver, followed by kidney and small intestine. The hepatic activity was located exclusively in microsomes. The apparent Michaelis constants were 2.5×1O-4M for the acceptor substrate and 1.0×1O-4M for S-adenosylmethionine. The activity was completely inhibited by p-chloromercuribenzoate, p-chloromercuribenzenesulfonate or HgCl2, whereas it was enhanced by GSH, cysteine or ascorbate.

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