Studies on protein methyltransferase in human cerebrospinal fluid.
Protein methyltransferases, rich in most mammalian brains, were studied in human cerebrospinal fluid (CSF). Among several well-characterized groups of methyltransferases, protein methylase I (S-adenosylmethionine:protein-arginine N-methyltransferase, EC 2.1.1.23) was found in significant amounts in human CSF samples. Both myelin basic protein (MBP) -specific and histone-specific protein methylase I activities were observed, the latter being generally higher in most CSF. S-Adenosyl-L-homocysteine, a potent product inhibitor for the methyltransferase, inhibited approximately 90% of MBP-specific protein methylase I activity at a concentration of 1 mM. The optimum pH of the MBP-specific protein methylase I was found to be around 7.2. Identity of exogenously added MBP as the methylated substrate for CSF enzyme was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An amino acid analysis of the [methyl-3H]protein hydrolysate showed two major radioactive peaks cochromatographing with monomethyl- and dimethyl (symmetric)-arginine. Human CSF contained relatively high endogenous protein methylase I activity (activity measured without added substrate protein): The endogenous substrate can be immunoprecipitated by antibody raised against calf brain MBP. Finally, CSF from several neurological patients were analyzed for protein methylase I, and the results are presented.
Park
J
J
Fels Research Institute, Temple University School of Medicine, Philadelphia, PA 19140.
Greenstein
J I
JI
Paik
W K
WK
Kim
S
S
D006801:Humans; D008745:Methylation; D008970:Molecular Weight; D009103:Multiple Sclerosis / Q000134:cerebrospinal fluid / Q000201:enzymology; D004676:Myelin Basic Protein / Q000302:isolation & purification; D009422:Nervous System Diseases / Q000134:cerebrospinal fluid / Q000201:enzymology; D011496:Protein Methyltransferases / Q000037:antagonists & inhibitors / Q000134:cerebrospinal fluid* / Q000302:isolation & purification; D012016:Reference Values; D012435:S-Adenosylhomocysteine / Q000494:pharmacology; D013379:Substrate Specificity
D004676:Myelin Basic Protein; D012435:S-Adenosylhomocysteine; D011496:Protein Methyltransferases