title: Homogeneous enzymatic assay for L-cysteine with betaC-S lyase.
abstract: We have developed a new enzymatic assay for determining L-cysteine concentration. The method involves the use of betaC-S lyase from Streptococcus anginosus, which catalyzes the alpha,beta-elimination of L-cysteine to hydrogen sulfide, pyruvate, and ammonia. The production of pyruvate is measured by D-lactate dehydrogenase and NADH. The decrease in NADH was proportional to the L-cysteine concentration up to 1.0 mM. When serum samples were used, within-day and day-to-day coefficient variations were below 4%. This method is simple, and can easily and reliably be used for accurate determination of L-cysteine concentration in serum or other samples.
authors.affiliation: Department of Biochemistry, Toyobo Co., Ltd., Tokyo, Japan. yoshiaki_nishiya@bio.toyobo.co.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nishiya
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Mamiko
authors.initials: M
authors.lastname: Yoshimura
authors.forename: Haruka
authors.initials: H
authors.lastname: Fukamachi
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Nakano
mesh_terms: D002138:Calibration; D003542:Cystathionine gamma-Lyase / Q000378:metabolism*; D003545:Cysteine / Q000032:analysis* / Q000097:blood / Q000378:metabolism; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009243:NAD / Q000032:analysis / Q000378:metabolism; D019289:Pyruvic Acid / Q000032:analysis / Q000378:metabolism; D015203:Reproducibility of Results; D034366:Streptococcus anginosus / Q000201:enzymology
chemical_list: D009243:NAD; D019289:Pyruvic Acid; D007770:L-Lactate Dehydrogenase; D003542:Cystathionine gamma-Lyase; D003545:Cysteine