Open AccessMetabolism of Isolated Kidney Tubules
Author(s) -
Guder Walter G.,
Wieland Otto H.
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03368.x
Subject(s) - pyruvate dehydrogenase phosphatase , pyruvate decarboxylation , pyruvate dehydrogenase complex , pyruvate dehydrogenase kinase , oxoglutarate dehydrogenase complex , biochemistry , branched chain alpha keto acid dehydrogenase complex , citric acid cycle , dihydroxyacetone , pyruvate carboxylase , dihydrolipoyl transacetylase , dehydrogenase , lactate dehydrogenase , malate dehydrogenase , biology , chemistry , metabolism , enzyme , glycerol
Pyruvate dehydrogenase activity was measured in extracts of isolated kidney cortex tubules, prepared by collagenase treatment. The measured activities were comparable to those described previously for whole kidney homogenates. Incubation of tubules in vitro in the absence of exogenous substrates led to a steady increase in enzyme activity over 30 min. This increase was not significantly changed by the addition of several gluconeogenic substrates including lactate, glutamine, glutamate, glycerol, fructose and malate. 1 mM oleate, 5 mM acetate and 20 mM 2‐oxoglutarate however, prevented this increase completely. In contrast, glucose and dihydroxyacetone accelerated the activation of pyruvate dehydrogenase during incubation in vitro. 20 mM pyruvate very rapidly activated pyruvate dehydrogenase with a following decrease below the activity of control experiments without substrate. 1 mM oleate and 20 mM 2‐oxoglutarate counteracted the increase in pyruvate dehydrogenase activity caused by glucose and dihydroxyacetone and had no effect in the presence of 20 mM pyruvate. Determination of the inactive part of pyruvate dehydrogenase after addition of purified pyruvate dehydrogenase phosphatase revealed that all changes observed were probably caused by enzymatic interconversion of pyruvate dehydrogenase. The results are compared with previously published observations on the regulation of pyruvate dehydrogenase in vivo and confirm the role of fatty acids in the regulation of kidney cortex pyruvate metabolism.