Enzymatic reactions of methionine sulfoximine. Conversion to the corresponding alpha-imino and alpha-keto acids and to alpha-ketobutyrate and methane sulfinimide.

摘要: L-Methionine sulfoximine is a substrate of L-amino acid oxidase (Crotalus adamanteus), glutamine transaminase, and gamma-cystathionase. In the reaction catalyzed by oxidase, methionine converted to aplph-imino-gamma-methylsulfoximinylbutyrate, which undergoes rapid gamma elimination yielding methane sulfinimide 2-imino-3-butenoic acid. Methane sulfonamide, sulfinic acid, sulfonic acid; hydrolyzed vinylglyoxylate, polymerizes an insoluble product. When carried out in presence semicarbazide, imine formed initially quantitatively trapped as alpha-keto-gamma-methylsulfoximinylbutyrate semicarbazone, from free alpha-keto may be obtained. mercaptan (RSH), exchange occurs leading formation new substituted position SR-group; thus, alpha-keto-gamma-(beta-hydroxyethiol)butyric (S-(hydroxyethyl)-2-keto-4-mercaptobutyric acid) was obtained when L-methionine oxidized 2-mercaptoethanol, enzymatic transamination this with L-glutamine gave amino L-omega-hydroxyethionine. The gamma-cystathionase yields 1 mol each alpha-ketobutyrate sulfinimide; latter almost exclusively Transamination corresponding (alpha-keto-gamma-methylsulfoximinylbutyrate), stable. Some these reactions occur vivo, thus contribute toxicity sulfoximine.