PT - JOURNAL ARTICLE AU - G L Larsen AU - J L Stevens TI - Cysteine conjugate beta-lyase in the gastrointestinal bacterium Eubacterium limosum. DP - 1986 Jan 01 TA - Molecular Pharmacology PG - 97--103 VI - 29 IP - 1 4099 - http://molpharm.aspetjournals.org/content/29/1/97.short 4100 - http://molpharm.aspetjournals.org/content/29/1/97.full SO - Mol Pharmacol1986 Jan 01; 29 AB - A cysteine conjugate beta-lyase (beta-lyase) from the gastrointestinal bacterium Eubacterium limosum has been isolated and characterized. This organism has the highest specific activity for cysteine conjugate beta-lyase of the gastrointestinal bacteria studied. The beta-lyase was found to cleave the thioether linkage of S-alkyl- and S-aryl-L-cysteine conjugates. Stoichiometric amounts of 2-mercaptobenzothiazole, pyruvic acid, and ammonia were produced from the beta-lyase cleavage of S-(2-benzothiazolyl)-L-cysteine. The enzyme activity was inhibited by hydroxylamine, iodoacetic acid, or KCN. The enzyme appears to be a 75,000-Da dimer of two 38,000-Da subunits. A natural substrate, cystathionine, was cleaved by this enzyme, indicating that this beta-lyase has beta-cystathionase activity. These data suggest that a beta-cystathionase from E. limosum may be an important enzyme in the metabolism of a wide range of cysteine conjugates of xenobiotics to thiol-containing products.