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Purification and Characterization of Two Distinct Isozymes of Protein Carboxymethylase from Bovine Brain
Author(s) -
Aswad Dana W.,
Deight Elizabeth A.
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb08147.x
Subject(s) - isoelectric focusing , isozyme , enzyme , biochemistry , polyacrylamide gel electrophoresis , gel electrophoresis , chemistry , pi , isoelectric point , sodium dodecyl sulfate , cytosol , substrate (aquarium) , chromatography , sodium , biology , organic chemistry , ecology
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.O. 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‐polyacryl‐amide 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 K m (1.2 μ M ), but it exhibited a low stoichiome‐try of methyl incorporation.