title: Similarities between cysteinesulphinate transaminase and aspartate aminotransferase.
abstract: A method for the purification of two cysteinesulphinate transaminases, A and B (EC 2.6.1), is described. These enzymes catalyse the conversion of cysteinesulphinic acid to beta-sulphinyl pyruvate. The final preparations are homogeneous by polyacrylamide gel electrophoresis, sodium dodecyl sulphate-polyacrylamide gel electrophoresis and isoelectrofocusing. The molecular weight of the subunits is 41 000 for cysteinesulphinate transaminase A and 43 400 for B. Both enzymes are unspecific, as L-asparate, L-glutamate and L-cysteic acid serve as substrates in addition to L-cysteinesulphinic acid. Cysteinesulphinate transaminase A has a Km of 9.8 mM for cysteinesulphinic acid and 0.25 mM for aspartic acid, whereas the B enzyme has a Km of 6.5 mM for cysteinesulphinic acid and 1.4 mM for aspartic acid. The Vmax values of the A and B enzymes are respectively 7.1 and 6.2 mmol h-1 mg-1 protein for aspartic acid and 45 and 9.3 mmol h-1 mg-1 protein for cysteinesulphinic acid. Both enzymes exhibit maximum activity at pH 8.6. A high specific activity is found in optimal conditions for these two transaminases, the pI values being 9.06 and 5.70 for cysteinesulphinate transaminase A and B respectively. These results have been compared with those already obtained for purified aspartate aminotransferase. Similarities in the pathways of taurine and gamma-aminobutyric acid (GABA) metabolism are discussed.
mesh_terms: D000375:Aging; D000818:Animals; D001219:Aspartate Aminotransferases / Q000032:analysis*; D001921:Brain / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D007525:Isoelectric Focusing; D007700:Kinetics; D051379:Mice; D009830:Olfactory Bulb / Q000201:enzymology; D051381:Rats; D012160:Retina / Q000201:enzymology; D013379:Substrate Specificity; D013654:Taurine / Q000378:metabolism; D000637:Transaminases / Q000032:analysis*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D013654:Taurine; D005680:gamma-Aminobutyric Acid; D000637:Transaminases; C019973:cysteine sulfinate transaminase; D001219:Aspartate Aminotransferases