Prasad, ChandanEdwards, R.M.2023-04-122023-04-121981This is the published version of an article that is available at https://doi.org/10.1016/s0021-9258(18)42996-1. Recommended citation: Prasad, C., & Edwards, R. M. (1981). Synthesis of phosphatidylcholine from phosphatidylethanolamine by at least two methyltransferases in rat pituitary extracts. Journal of Biological Chemistry, 256(24), 13000–13003. https://doi.org/10.1016/s0021-9258(18)42996-1. This item has been deposited in accordance with publisher copyright and licensing terms and with the author’s permission.https://hdl.handle.net/11274/14817https://doi.org/10.1016/s0021-9258(18)42996-1Article originally published in Journal of Biological Chemistry, 256(24), 13000–13003. English. Published Online 2021. https://doi.org/10.1016/s0021-9258(18)42996-1Rat pituitary extracts contain at least two methyltransferases that methylate phosphatidylethanolamine to phosphatidylcholine using S-adenosylmethionine as the methyl donor. The first enzyme methylates phosphatidylethanolamine to phosphatidyl-N-monomethylethanolamine and has a high Km (40-42 microM) for S-adenosylmethionine, whereas the second enzyme(s) catalyzes two successive methylations of phosphatidyl-N-monomethylethanolamine to phosphatidyl-N,N-dimethylethanolamine and then to phosphatidylcholine and has a low Km (6.7 microM) for S-adenyl-L-methionine. The first enzyme is loosely bound to the membrane fraction; therefore it appears in both particulate (20,000 X g) and supernatant (20,000 X g) fractions, whereas the second enzyme(s) is tightly bound to the membrane and thus appears only in the particulate fraction. Both methyltransferases have two pH optima of 6.5 and 9.5 (9.5 activity greater than 6.5 activity) and they do not require Mg2+.en-USPituitary physiologyPhospholipid methylationMethyltransferase activityArticleCC BY-NC-ND