L-lanthionine oxidation by snake venom L-amino acid oxidase.

L-Lanthionine is oxidized by snake venom L-amino acid oxidase with the release of one mole of ammonia per mole of lanthionine. Spectrophotometric, chromatographic, and analytical properties are all consistent with the identification of the mono-keto derivative of lanthionine as the first enzymatic product of the reaction. This then cyclizes into a dihydrothiazine dicarboxylic acid which is further subject to spontaneous changes. Authentic samples of the thiazine derivative have been prepared by interacting L-cysteine with bromopyruvic acid. The properties of the synthetic product are described and compared with those exhibited by the enzymatic product.