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INDUCTION AND PROPERTIES OF PYRUVATE KINASE OF THE CEREBRAL HEMISPHERE OF RATS OF VARIOUS AGES 1
Author(s) -
Chainy G. B. N.,
Kanungo M. S.
Publication year - 1978
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.1471-4159.1978.tb06546.x
Subject(s) - endocrinology , medicine , pyruvate kinase , testosterone (patch) , castration , enzyme assay , incubation , enzyme , chemistry , biology , metabolism , hormone , glycolysis , biochemistry
— The induction of pyruvate kinase (ATP: pyruvate 2‐ O phosphotransferase, EC 2.7.1.40; PK) by estradiol or testosterone in the cerebral hemisphere of male and female rats of different ages was studied. There is a marked decrease in the activity of the enzyme of normal male and female rats with increasing age. Orchiectomy decreases its activity in young and old rats, but not in adult rats. Ovariectomy decreases its activity significantly in all the ages. Estradiol (50μg/100g body wt.) induces its activity in castrated male and female rats, but its effect is greater in female rats. A higher dose of estradiol (100μg/100g body wt.) has age‐ and sex‐dependent induction. Testosterone (50 and 100μg/100g body wt.) has very little effect on its activity in castrated male and female rats of the three ages. The K m values for PEP and ADP, and the K t values for ATP and l ‐phenylalanine for the partially purified enzyme of the cerebral hemisphere of normal young and old rats are the same. Preincubation of the enzyme with l ‐alanine reverses the l ‐phenylalanine induced inhibition. The concentration of l ‐alanine required for this effect is the same for both ages. The concentration of Mg 2+ required to reverse the inhibitory effect of ATP is the same for young and old rats. Estradiol and testosterone added directly to the incubation mixture do not have any effect on the enzyme activity. These data suggest that the nature of the enzyme molecule does not change with age, but that its induction properties change with age.