Nucleoside Diphosphate-sugar 4-Epimerases I. Uridine Diphosphate Glucose 4-Epimerase of Wheat Germ.
Nucleoside Diphosphate-sugar 4-Epimerases I. Uridine Diphosphate Glucose 4-Epimerase of Wheat Germ.
复制标题
核苷二磷酸-糖4-差向异构酶I.麦芽的尿苷二磷酸葡萄糖4-差向异构酶。
作者：
D. Fan;D. Feingold
采用MnCl(2)处理、（nh4）(2) (2)SO(4)分离、Sephadex柱层析、磷酸钙凝胶吸附和洗脱等方法，从小麦胚芽提取物中纯化出尿苷二磷酸(UDP)-葡萄糖4-epimerase (EC 5.1.3.2)，纯度超过1000倍。酶的最适pH为9.0。udp -d-半乳糖的Km值为0.1 mm， udp -d-葡萄糖的Km值为0.2 mm。NAD是活动所必需的；K(a) = 0.04 mm。NADH是一种与NAD严格竞争的抑制剂；K(i) = 2mum。小麦胚芽中还含有不同于udp -葡萄糖4-外亚基酶的udp -l-阿拉伯糖4-外亚基酶（EC 5.1.3.5）和胸苷二磷酸(TDP)-葡萄糖4-外亚基酶。
Uridine diphosphate (UDP)-glucose 4-epimerase (EC 5.1.3.2) has been purified over 1000-fold from extracts of wheat germ by MnCl(2) treatment, (NH(4))(2)SO(4) fractionation, Sephadex column chromatography, and adsorption onto and elution from calcium phosphate gel. The enzyme has a pH optimum of 9.0. Km values are 0.1 mm for UDP-d-galactose and 0.2 mm for UDP-d-glucose. NAD is required for activity; K(a) = 0.04 mm. NADH is an inhibitor strictly competitive with NAD; K(i) = 2 mum. Wheat germ also contains UDP-l-arabinose 4-epimerase (EC 5.1.3.5) and thymidine diphosphate (TDP)-glucose 4-epimerase which are distinct from UDP-glucose 4-epimerase.