Nieto A, Catt K J
Endocrinology. 1983 Aug;113(2):758-62. doi: 10.1210/endo-113-2-758.
Hormonal stimulation of purified rat Leydig cells with hCG caused a 2-fold increase in phospholipid methyltransferase activity within 10 min. This effect of gonadotropin was concentration dependent, with maximal activation of methyltransferase at 10(-12) M hCG, and was reproduced by 8-bromo-cAMP. Hormonal activation of phospholipid methyltransferase caused an increase in the maximum velocity of the enzyme, without changing the Km for S-adenosylmethionine. Analysis of the pattern of radiolabeled phospholipids from Leydig cells showed that the incorporation of methyl groups and the increase in phospholipid methylation stimulated by 8-bromo-cAMP occurred mainly in phosphatidyl-N-monomethylethanolamine. The rapid and highly sensitive increase in phospholipid methylation in hCG-stimulated Leydig cells is consistent with a role of methyltransferase in the hormonal activation mechanism probably at a step subsequent to cAMP production.
用人绒毛膜促性腺激素（hCG）对纯化的大鼠睾丸间质细胞进行激素刺激，可在10分钟内使磷脂甲基转移酶活性增加2倍。促性腺激素的这种作用具有浓度依赖性，在10^(-12) M hCG时甲基转移酶的激活作用最强，且8-溴环磷酸腺苷（8-bromo-cAMP）也能产生同样的效果。激素对磷脂甲基转移酶的激活作用导致该酶的最大反应速度增加，而对S-腺苷甲硫氨酸的米氏常数（Km）没有影响。对睾丸间质细胞中放射性标记磷脂模式的分析表明，8-溴环磷酸腺苷刺激的甲基基团掺入和磷脂甲基化增加主要发生在磷脂酰-N-单甲基乙醇胺中。hCG刺激的睾丸间质细胞中磷脂甲基化的快速且高度敏感的增加，与甲基转移酶在激素激活机制中可能在环磷酸腺苷产生之后的某个步骤中所起的作用相一致。
