Modulation by the ratio S-adenosylmethionine/S-adenosylhomocysteine of cyclic AMP-dependent phosphorylation of the 50 kDa protein of rat liver phospholipid methyltransferase.
The present results show that the catalytic subunit of cyclic AMP-dependent protein kinase phosphorylates the 50 kDa protein of rat liver phospholipid methyltransferase at one single site on a serine residue. Phosphorylation of this site is stimulated 2- to 3-fold by S-adenosylmethionine. S-adenosylmethionine-dependent protein phosphorylation is time- and dose-dependent and occurs at physiological concentrations. S-adenosylhomocysteine has no effect on protein phosphorylation but inhibits S-adenosylmethionine-dependent protein phosphorylation. S-Adenosylmethionine/S-adenosylhomocysteine ratios varying from 0 to 5 produce a dose-dependent stimulation of the phosphorylation of the 50 kDa protein. In conclusion, these results show, for the first time, that the ratio S-adenosylmethionine/S-adenosylhomocysteine can modulate phosphorylation of a specific protein.
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D005459:Fluorides / Q000494:pharmacology; D006710:Homocysteine / Q000031:analogs & derivatives*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008780:Methyltransferases / Q000378:metabolism*; D008970:Molecular Weight; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D050918:Phosphatidylethanolamine N-Methyltransferase; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D012435:S-Adenosylhomocysteine / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000378:metabolism*
D006710:Homocysteine; D012436:S-Adenosylmethionine; D012435:S-Adenosylhomocysteine; D000242:Cyclic AMP; D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase; D050941:Phosphatidyl-N-Methylethanolamine N-Methyltransferase; D011494:Protein Kinases; D005459:Fluorides