title: Purification and characterization of two distinct isozymes of protein carboxymethylase from bovine brain.
abstract: Protein carboxymethylase (EC 2.1.1.24) from cytosol of bovine brain was found to exist as two apparent isozymes that could be separated by chromatography on DEAE-cellulose at pH 8.0. Rechromatography of the two forms, designated PCM I and PCM II, indicated that they are not interconvertible. Both enzymes have a molecular weight of 24,300 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, PCM I consists mainly of one isoelectric form, pI 6.5, whereas PCM II resolves into two forms of pI 5.6 and 5.7. The relative amounts of PCM I and PCM II show a marked tissue dependence. Brain has approximately twice as much PCM I as II, whereas liver contains only the type II enzyme. The two enzymes were found to have similar substrate specificities when tested with five different methyl-accepting proteins. Synapsin I, a basic protein associated with synaptic vesicles, was found to be an excellent methyl-accepting protein with regard to its Km (1.2 microM), but it exhibited a low stoichiometry of methyl incorporation.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D002540:Cerebral Cortex / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D007527:Isoenzymes / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D008970:Molecular Weight; D011496:Protein Methyltransferases / Q000302:isolation & purification*; D011497:Protein O-Methyltransferase / Q000302:isolation & purification* / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D007527:Isoenzymes; D011496:Protein Methyltransferases; D011497:Protein O-Methyltransferase