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Microsomal phosphatidylethanolamine methyltransferase: Inhibition by S‐adenosylhomocysteine
Author(s) -
Hoffman Dennis R.,
Haning Judy A.,
Cornatzer W. E.
Publication year - 1981
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02534900
Subject(s) - lipidology , phosphatidylethanolamine , clinical chemistry , microsome , methyltransferase , chemistry , biochemistry , o methyltransferase , enzyme , phospholipid , methylation , phosphatidylcholine , gene , membrane
Inhibition by S‐adenosylhomocysteine (AdoHcy) of the three reactions of phosphatidylethanolamine methyltransferase which catalyzes the production of phosphatidylcholine from phosphatidyl‐ethanolamine in guinea pig and rat liver microsomes has been evaluated. Five of the six methylation reactions in these two species exhibit greater affinity for inhibitor, AdoHcy, than for substrate, S‐adenosylmethionine (AdoMet). The Ki values for the rate‐limiting reactions were 3.8 μM and 68 μM in rat and guinea pig livers, respectively. An AdoMet:AdoHcy ratio of 12∶1 in developing liver was found to decline to a constant value in the adult of 5∶1. The concentration of AdoHcy in rat and guinea pig liver increases markedly following death of the animal. A concomitant decrease in the AdoMet level was observed in guinea pig liver. A comparison of phosphatidylethanolamine methyl‐transferase activity with the hepatic concentrations of AdoMet and AdoHcy in mouse, rat, rabbit and guinea pig is presented. Regulation of the methylation pathway is discussed.