Rao K N
Radiation Biology and Biochemistry Division, Bhabha Atomic Research Centre, Bombay, India.
Indian J Biochem Biophys. 1993 Feb;30(1):26-35.
Thymidylate synthase (5, 10-methylenetetrahydrofolate: dUMP C-methyltransferase, EC 2.1.1.45) from crude cell extracts of Lactobacillus leichmannii has been purified 190-fold to homogeneity by chromatography on hydroxylapatite, DEAE-cellulose and Sephadex G-100 columns. It has UV absorption maxima at 280 nm. The crude extracts, however, have RNA associated with the native enzyme. This is in line with our earlier observation on the Streptococcus faecium thymidylate synthase [Narasimha Rao K & Kisliuk R L, (1983) Proc Natl Acad Sci USA, 80, 916-920]. Optimal conditions for dTMP synthase activity are: 275 microM (dl)-L-H4PteGlu, 13 mM HCHO, 13 mM MgCl2, 100 microM dUMP and 75 mM 2-mercaptoethanol at pH 7.4 using Tris-HCl buffer. The enzyme has M(r) of 74 kDa, Stokes radius of 1.24 nm and a sedimentation coefficient value of 0.45 S. The enzyme is a dimer composed of 2 identical subunits each with M(r) of 37 kDa.
从莱氏乳杆菌的粗细胞提取物中获得的胸苷酸合酶（5,10-亚甲基四氢叶酸：dUMP C-甲基转移酶，EC 2.1.1.45），通过在羟基磷灰石、DEAE-纤维素和葡聚糖G-100柱上进行色谱分离，已被纯化190倍至同质状态。它在280 nm处有紫外吸收最大值。然而，粗提取物中有与天然酶相关的RNA。这与我们早期对粪肠球菌胸苷酸合酶的观察结果一致[Narasimha Rao K和Kisliuk R L，（1983年）《美国国家科学院院刊》，80，916 - 920]。dTMP合酶活性的最佳条件是：在pH 7.4下，使用Tris - HCl缓冲液，含有275 microM（dl）-L-H4PteGlu、13 mM甲醛、13 mM氯化镁、100 microM dUMP和75 mM 2-巯基乙醇。该酶的相对分子质量为74 kDa，斯托克斯半径为1.24 nm，沉降系数值为0.45 S。该酶是由2个相同亚基组成的二聚体，每个亚基的相对分子质量为37 kDa。
