Staton A L, Mazelis M
Department of Food Science and Technology, University of California, Davis 95616.
Arch Biochem Biophys. 1991 Oct;290(1):46-50. doi: 10.1016/0003-9861(91)90589-b.
S-Substituted cysteines and their derivatives are prominent secondary amino acids in a number of plant families. The substituents are often specific and unique to each family. Cystathionine, however, is an ubiquitous S-substituted cysteine found in all autotrophic plants since it is an intermediate in the biosynthesis of methionine. beta-Cystathionase will produce homocysteine and pyruvate from cystathionine by a beta-elimination reaction. The present report describes the purification of this enzyme to homogeneity from spinach leaves and some of its properties. The enzyme has a molecular weight of 210,000 and consists of four identical subunits of Mr 53,000. It has a pH optimum for activity of 8.6-8.7 and utilizes pyridoxal-5'-phosphate as a cofactor. Its specificity is limited to L-cystathionine, L-djenkolate, and L-cystine as substrates with a relative activity of 100:126:17, respectively. It is not a glycoprotein unlike a number of previously described plant C-S lyases.
S-取代半胱氨酸及其衍生物是许多植物科中重要的仲氨基酸。取代基通常对每个科来说都是特定且独特的。然而，胱硫醚是一种在所有自养植物中都存在的S-取代半胱氨酸，因为它是甲硫氨酸生物合成中的一个中间体。β-胱硫醚酶通过β-消除反应可从胱硫醚生成高半胱氨酸和丙酮酸。本报告描述了从菠菜叶中纯化该酶至均一状态及其一些性质。该酶的分子量为210,000，由四个分子量为53,000的相同亚基组成。其最适pH值为8.6 - 8.7，以磷酸吡哆醛作为辅因子。其特异性仅限于L-胱硫醚、L-豆磺隆和L-胱氨酸作为底物，相对活性分别为100:126:17。与许多先前描述的植物C-S裂解酶不同，它不是糖蛋白。
