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REGULATION OF PYRUVATE KINASE IN THE RAT CEREBRAL CORTEX 1
Author(s) -
Schwark W. S.,
Singhal R. L.,
Ling G. M.
Publication year - 1971
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.1471-4159.1971.tb00174.x
Subject(s) - pyruvate kinase , enzyme , cerebral cortex , biochemistry , pyruvic acid , enzyme assay , biology , chemistry , endocrinology , medicine , glycolysis
—The distribution of pyruvate kinase (ATP: pyruvate phosphotransferase; EC 2.7.1.40) in several areas of the central nervous system, the ontogenic changes in the cerebro‐cortical enzyme, and its modulation by certain metabolites were investigated in the rat. No significant differences in activity of pyruvate kinase in different regions of the nervous system were detected when activity was expressed per g of tissue. Studies on the ontogeny of pyruvate kinase in cerebral cortex revealed extremely low levels of enzymic activity at birth. A two‐fold increase occurred between 1 and 20 days of postnatal age, with a further two‐fold increase between 20 and 60 days of age. l ‐Phenylalanine, when added directly into the reaction mixture, produced a dose‐dependent inhibition of cerebro‐cortical pyruvate kinase; a similar inhibition of the enzyme activity was observed with copper. The inhibition by l ‐phenylalanine and copper was prevented and reversed by l ‐alanine. Although the cerebro‐cortical enzyme was resistant to thermal inactivation at 37°C, incubation of the enzyme preparation at 55°C for 60 min resulted in approximately 60 per cent inhibition of its activity. Preincubation with l ‐alanine provided partial protection against thermal inactivation of the enzyme. Although l ‐alanine exerted no effect on the non‐competitive inhibition of pyruvate kinase produced by calcium, such inhibition was prevented and reversed by EDTA. The sulphydryl inhibitor, P ‐chloromercuribenzoate, produced a dose‐dependent inhibition of cerebro‐cortical pyruvate kinase, whereas addition of penicillamine resulted in a slight activation of the enzyme. Although inhibition of pyruvate kinase by P ‐chloromercuribenzoate was unaffected by l ‐alanine, penicillamine effectively prevented and reversed the inhibition produced by P ‐chloromercuribenzoate.