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Two Isoenzymes of Na + , K + ‐ATPase Have Different Kinetics of K + Dephosphorylation in Normal Cat and Human Brain Cortex
Author(s) -
Guillaume D.,
Grisar T.,
DelgadoEscueta A. V.,
Laschet J.,
BureauHeeren M.
Publication year - 1990
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.1471-4159.1990.tb13292.x
Subject(s) - dephosphorylation , phosphoprotein , phosphorylation , sodium dodecyl sulfate , sodium , chemistry , gel electrophoresis , atpase , cortex (anatomy) , extracellular , polyacrylamide gel electrophoresis , biochemistry , enzyme , microbiology and biotechnology , phosphatase , biology , neuroscience , organic chemistry
Analysis of purified Na + , K + ‐ATPase from cat and human cortex by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis reveals two large catalytic subunits called α(‐) (lower molecular weight) and α(+) (higher molecular weight). Differences in K + dephosphorylation of these two molecular forms have been investigated by measuring the phosphorylation level of each protein after their separation on sodium dodecyl sulfate gels. In the presence of Na + , Mg 2+ , and ATP, both subunits are phosphorylated. Increasing concentrations (from 0 to 3 m M ) of K + induce progressive dephosphorylation of both α‐subunits, although the phosphoprotein content of α(‐) is decreased significantly less than that of α(+). K a values of α(‐) for K + are 40% and 50% greater in cat and human cortex, respectively, than values of α(+), α(‐) and α(+) are thought to be localized in specific cell types of the brain: α(‐) is the exclusive form of nonneuronal cells (astrocytes), whereas α(+) is the only form of axolemma. Our results support the hypothesis that glial and neuronal Na + , K + ‐ATPases are different molecular entities differing at least by their K + sensitivity. Results are discussed in relation to the role of glial cells in the regulation of extracellular K + in brain.