Panagia V, Ganguly P K, Okumura K, Dhalla N S
J Mol Cell Cardiol. 1985 Dec;17(12):1151-9. doi: 10.1016/s0022-2828(85)80111-5.
Synthesis of phosphatidylcholine (PC) by S-adenosyl-L-methionine (AdoMet)-dependent methylation of phosphatidylethanolamine (PE) has been recently characterized in rat heart sarcolemma obtained by hypotonic shock-LiBr treatment method. The present study, employing different procedures for the isolation of purified cardiac sarcolemmal membranes in rat, confirms the existence of three catalytic sites which are specifically involved in the sequential methyl transfer reactions from PE to PC. Other subcellular organelles such as sarcoplasmic reticulum (microsomes) and mitochondria showed methyltransferase activity which was absent in myofibrils and in cytosolic fraction. Experiments with several concentrations of AdoMet revealed that the kinetic pattern of methyltransferase activity in both microsomes and mitochondria was comparable to that obtained in sarcolemma. In addition, the characteristics of three catalytic sites as identified by the synthesis of phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine and PC in these subcellular organelles were similar to those of sarcolemma. The results are consistent with the view that methyltransferase activity is localized in different membrane systems of the myocardium.
最近，通过低渗休克-LiBr处理法获得的大鼠心脏肌膜中，已对磷脂酰乙醇胺（PE）经S-腺苷-L-甲硫氨酸（AdoMet）依赖性甲基化合成磷脂酰胆碱（PC）进行了表征。本研究采用不同方法分离大鼠纯化的心脏肌膜，证实存在三个催化位点，它们具体参与从PE到PC的顺序甲基转移反应。其他亚细胞器，如肌浆网（微粒体）和线粒体，显示出甲基转移酶活性，而肌原纤维和胞质部分则没有这种活性。用几种浓度的AdoMet进行的实验表明，微粒体和线粒体中甲基转移酶活性的动力学模式与在肌膜中获得的模式相当。此外，通过在这些亚细胞器中合成磷脂酰-N-单甲基乙醇胺、磷脂酰-N，N-二甲基乙醇胺和PC所确定的三个催化位点的特征与肌膜的相似。这些结果与甲基转移酶活性定位于心肌不同膜系统的观点一致。
