Anfuso C D, Sipione S, Lupo G, Alberghina M
Institute of Biochemistry, Faculty of Medicine, University of Catania, Italy.
Comp Biochem Physiol B Biochem Mol Biol. 1995 Nov;112(3):493-501. doi: 10.1016/0305-0491(95)00108-5.
While steady-state kinetic parameters (metabolite pools, Km and activation energies) are partially known for the enzymes involved in phosphatidylcholine synthesis and degradation in mammalian brain, they are not available for the nervous system of lower vertebrates or invertebrates. Since the extent of evolutionary development of an enzyme is not known a priori, we evaluated the kinetic and thermodynamic parameters of choline kinase, CTP:phosphocholine cytidylyltransferase, choline phosphotransferase and glycerophosphorylcholine phosphodiesterase in squid (Loligo pealei) optic lobe, dogfish (Mustelus canis) and rat brain. For all these enzyme activities, basic similarities in Km and inhibitor effect were found. The same was true for the activation energies Ea, with the exception of squid choline kinase and dogfish cytidylyltransferase. Treatment of microsomal membranes with phospholipase C sharply inhibited cytidylyltransferase activity in all three animal species. In dogfish brain, glycerophosphorylcholine phosphodiesterase activity was undetectable. Our results are consistent with the notion that the kinetic properties of the enzyme activities leading to the preservation of the phosphatidylcholine membranous pool may have appeared early in metazoan evolution and been fully conserved in mammals.
虽然参与哺乳动物大脑中磷脂酰胆碱合成与降解的酶的稳态动力学参数（代谢物池、米氏常数和活化能）已部分为人所知，但对于低等脊椎动物或无脊椎动物的神经系统而言，这些参数尚不可知。由于一种酶的进化发展程度无法预先得知，我们评估了鱿鱼（莱氏拟乌贼）视叶、角鲨（犬鲨）和大鼠大脑中胆碱激酶、CTP：磷酸胆碱胞苷转移酶、胆碱磷酸转移酶和甘油磷酸胆碱磷酸二酯酶的动力学和热力学参数。对于所有这些酶活性，在米氏常数和抑制剂效应方面发现了基本相似之处。活化能Ea也是如此，除了鱿鱼胆碱激酶和角鲨胞苷转移酶。用磷脂酶C处理微粒体膜会显著抑制所有三种动物物种中的胞苷转移酶活性。在角鲨大脑中，未检测到甘油磷酸胆碱磷酸二酯酶活性。我们的结果与以下观点一致，即导致磷脂酰胆碱膜池得以维持的酶活性的动力学特性可能在多细胞动物进化早期就已出现，并在哺乳动物中得到了完全保留。
