Open AccessThe Physiological Role of Pyruvate Carboxylation in Hamster Brown Adipose Tissue
Author(s) -
CAN Barbara,
NEDERGAARD Jan
Publication year - 1979
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1979.tb12909.x
Subject(s) - pyruvate carboxylase , citric acid cycle , pyruvate decarboxylation , biochemistry , carboxylation , chemistry , gluconeogenesis , brown adipose tissue , pyruvate dehydrogenase complex , pyruvate dehydrogenase kinase , phosphoenolpyruvate carboxykinase , respiration , mitochondrion , biology , metabolism , adipose tissue , enzyme , catalysis , botany
1 Pyruvate carboxylase is present in brown adipose tissue mitochondria. 2 In isolated mitochondria, pyruvate, bicarbonate and ATP, the substrates for pyruvate carboxylase, are able to replace added malate in supplying a condensing partner for acetyl‐CoA formed from β‐oxidation of fatty acids. 3 In brown adipocytes, pyruvate and CO 2 increase the rate of norepinephrine‐stimulated respiration synergistically. 4 The norepinephrine‐stimulated respiration in brown adipocytes is diminished when pyruvate transport into the mitochondria is inhibited. 5 Pyruvate carboxylation increases the intramitochondrial level of citric acid cycle intermediates, as shown by titrations of malonate inhibition of respiration. 6 Pyruvate carboxylation can continuously supply the mitochondria with citric acid cycle intermediates, as evidenced by its ability to maintain respiration when oxoglutarate conversion to glutamate is stimulated. 7 Pyruvate carboxylation is necessary for maximal oxygen consumption even when drainage of the citric acid cycle for amino acid synthesis is eliminated. 8 Pyruvate carboxylation explains observed effects of CO 2 on respiration in brown adipocytes, and may also explain the increased glucose uptake by brown adipose tissue during thermogenesis in vivo .