Wilkes J, Cornish R A, Mettrick D F
J Parasitol. 1981 Dec;67(6):832-40.
A method is described for the purification of the enzyme phosphoenolpyruvate carboxykinase (PEPCK) from the cestode Hymenolepis diminuta. When purified to electrophoretic homogeneity, the enzyme had a molecular weight of 70,600 and an isoelectric point of 7.5. Kinetic studies indicated that the pH 5.6 was optimal for the carboxylation reaction and that Mn++ was the preferred divalent cation; there was no activity of the enzyme in the presence of Mg++. Apparent Km values for the carboxylation reaction were determined; those for GDP (20.6 muM) and PEP (38.9 muM) were lower than the values previously reported. GTP, GMP, ITP, IMP, fumarate, succinate and alpha-ketoglutarate were found to be competitive inhibitors and their Ki values determined.
描述了一种从微小膜壳绦虫中纯化磷酸烯醇丙酮酸羧激酶（PEPCK）的方法。纯化至电泳纯时，该酶的分子量为70,600，等电点为7.5。动力学研究表明，pH 5.6是羧化反应的最佳pH值，Mn++是首选的二价阳离子；在Mg++存在下该酶无活性。测定了羧化反应的表观Km值；GDP（20.6 μM）和PEP（38.9 μM）的表观Km值低于先前报道的值。发现GTP、GMP、ITP、IMP、富马酸、琥珀酸和α-酮戊二酸是竞争性抑制剂，并测定了它们的Ki值。
