title: Purification and characterization of cysteine conjugate transaminases from rat liver.
abstract: 1. Soluble cysteine-conjugate alpha-ketoglutarate transaminase (CAT-I) was purified about 670-fold from rat liver cytosol using s-(p-bromophenyl)-L-cysteine as amino acid substrate. The enzyme preparation of the final step of purification showed a single band in polyacrylamide gel electrophoresis. CAT-I accounted for 64% of the transaminase activity in cytosol. 2. The mol. wt of the enzyme was about 64,000 as determined by gel filtration. Respective Km values for s-(p-bromophenyl)-L-cysteine and alpha-ketoglutaric acid were 1.0 and 1.3 mM in Tris-acetate buffer (pH 7.0). Aminooxyacetic acid, hydroxylamine, and KCN inhibited the enzyme activity. 3. In addition to CAT-I, two isozymes (CAT-IIA and CAT-IIB) were partially purified from rat liver cytosol. In respect of mol. wt, substrate specificity towards cysteine conjugates, and several other properties, CAT-IIA and CAT-IIB were very similar to CAT-I. However, differences were observed for these enzymes in the rate of reverse reaction (formation reaction of cysteine conjugates and alpha-ketoglutaric acid) and substrate specificity towards L-aspartic acid and L-cysteinesulphinic acid.
authors.affiliation: Nippon Roche Research Centre, Kanagawa Prefecture, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tomisawa
authors.forename: N
authors.initials: N
authors.lastname: Ichimoto
authors.forename: Y
authors.initials: Y
authors.lastname: Takanohashi
authors.forename: S
authors.initials: S
authors.lastname: Ichihara
authors.forename: H
authors.initials: H
authors.lastname: Fukazawa
authors.forename: M
authors.initials: M
authors.lastname: Tateishi
mesh_terms: D000818:Animals; D002845:Chromatography; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D003545:Cysteine / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D017886:Durapatite; D006882:Hydroxyapatites; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D051381:Rats; D013379:Substrate Specificity; D000637:Transaminases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D006882:Hydroxyapatites; D007527:Isoenzymes; D017886:Durapatite; D000637:Transaminases; C058685:cysteine conjugate transaminase; D003545:Cysteine