title: Protein-O-methyltransferase in brain synaptosomal fraction under normal, ischemic and hypoxic conditions. Possible role in neuronal function.
abstract: Activity of protein-O-methyltransferase in synaptosomal fractions was obtained. Km values calculated for S-adenosylmethionine as substrate were 1 microM and Vmax = 4.3 pmoles/mg p/min. In the presence of gelatin (exogenous protein acceptor), activity was about 3 times higher. Without gelatin, activity of endogenous protein-O-methyltransferase decreased by about 20% under hypoxic conditions and by about 15% in ischemia. Exogenous activity under both hypoxic and ischemic conditions did not change. These results can possibly be explained by the changes in methyl acceptor proteins. In normal conditions, after inhibition methylcarboxylation by S-adenosyl-L-homocysteine, the decrease of GABA uptake and increase in the uptake of dopamine were observed. Uptake of serotonine and noradrenaline were unchanged.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology; D002545:Brain Ischemia / Q000201:enzymology*; D002534:Hypoxia, Brain / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D018377:Neurotransmitter Agents / Q000378:metabolism; D011496:Protein Methyltransferases / Q000378:metabolism*; D011497:Protein O-Methyltransferase / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012436:S-Adenosylmethionine / Q000378:metabolism; D009435:Synaptic Transmission; D013574:Synaptosomes / Q000201:enzymology*
chemical_list: D018377:Neurotransmitter Agents; D012436:S-Adenosylmethionine; D011496:Protein Methyltransferases; D011497:Protein O-Methyltransferase