Enzymatic Studies on the Metabolism of the Tetrahydrofurfuryl Mercaptan Moiety of Thiamine Tetrahydrofurfuryl Disulfide:III. Oxidative Cleavage of the Tetrahydrofuran Moiety

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  • FUJITA Takeshi
    Biological Research Laboratories, Central Researche Division, Takeda Chem. Ind., Ltd.
  • SUZUOKI Ziro
    Biological Research Laboratories, Central Researche Division, Takeda Chem. Ind., Ltd.

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Description

In vitro metabolism of the tetrahydrofuran ring was studied using [35S]methyl tetrahydrofurfuryl sulfone as a substrate with rat liver homogenates. The tetrahydrofuran ring was first hydroxylated by liver microsomes in the presence of NADPH and O2. The reaction product was isolated and identified as methyl 5-hydroxytetrahydrofurfuryl sulfone by instrumental analyses of the infrared, nuclear magnetic resonance, and mass spectra. An NADH-generating system could not support this microsomal hydroxylation, and the involvement of a peroxidative reaction was excluded. Methyl 5-hydroxytetrahydrofurfuryl sulfone thus formed was further oxidized to 4-hydroxy-5-methylsulfonylvaleric acid by incubation with the hepatic cytosol. Microsomes were no longer necessary for the second reaction. These results indicated that the tetrahydrofuran ring was first hydroxylated at the 5-position by microsomes and further cleaved to the straight-chain fatty acid via the intermediate formation of either an aldehyde form or a γ-lactone in the presence of cytosol.

Journal

  • J Biochem (Tokyo)

    J Biochem (Tokyo) 74 (4), 733-738, 1973

    The Japanese Biochemical Society

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