Hart G J, Battersby A R
Biochem J. 1985 Nov 15;232(1):151-60. doi: 10.1042/bj2320151.
Uroporphyrinogen III synthase (co-synthetase) purified from Euglena gracilis is a monomer of Mr 38 500 by gel-filtration studies and 31 000 by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The pI is apparently in the range 4.8-5.1. No evidence for any cofactors was found, and folate derivatives were shown to be absent; no metal ions appear to be present in the enzyme. The Km for hydroxymethylbilane is in the range 12-40 microM, and the product, uroporphyrinogen III, is an inhibitor. Modification studies suggest that arginine residues are essential for the activity of co-synthetase; lysine residues may also be essential, but histidine, cysteine and tyrosine residues are not.
从纤细裸藻中纯化得到的尿卟啉原III合酶(共合成酶),通过凝胶过滤研究表明其为分子量38500的单体,而通过十二烷基硫酸钠/聚丙烯酰胺凝胶电泳测定为31000。其等电点明显在4.8 - 5.1范围内。未发现任何辅助因子的证据,且显示不存在叶酸衍生物;该酶中似乎不存在金属离子。对羟甲基胆色素的米氏常数在12 - 40微摩尔范围内,且产物尿卟啉原III是一种抑制剂。修饰研究表明精氨酸残基对于共合成酶的活性至关重要;赖氨酸残基可能也必不可少,但组氨酸、半胱氨酸和酪氨酸残基并非如此。