Hepatocytes, isolated from fasted rats, were incubated with graded concentrations of lactate and pyruvate, at a mean constant ratio of 10-13:1, to alter systematically the concentrations of gluconeogenic intermediate metabolites and rates of glucose production. By analyzing glucose production rates as a function of corresponding concentrations of extracellular pyruvate, cytosolic oxalacetate, a...

The cyclic AMP-dependent protein kinase (isoenzymes I and II) was measured using a synthetic peptide analog of the porcine hepatic phosphorylation site sequence (Leu-Arg-Arg-Ala-Ser-&eu-Gly). Epinephrine caused a timeand dose-dependent activation of the hepatic cyclic AMP-dependent protein kinase and inactivation of pyruvate kinase. Maximal activation of the protein kinase occurred within 1 min...

OBJECTIVE Pyruvate dehydrogenase complex (PDC) serves as the metabolic switch between glucose and fatty acid utilization. PDC activity is inhibited by PDC kinase (PDK). PDC shares the same substrate, i.e., pyruvate, as glyceroneogenesis, a pathway controlling fatty acid release from white adipose tissue (WAT). Thiazolidinediones activate glyceroneogenesis. We studied the regulation by rosiglita...

Pyruvate kinase plays a critical role in cellular metabolism of glucose by serving as a major regulator of glycolysis. This tetrameric enzyme is allosterically regulated by different effector molecules, mainly phosphosugars. In response to binding of effector molecules and substrates, significant structural changes have been identified in various pyruvate kinase structures. Pyruvate kinase of C...

Pyruvate kinase (ATP: pyruvate phosphotransferase, EC 2.7.1.40) was partially purified from cotton seeds. The enzyme shows normal kinetics toward phosphoenolpyruvate, ADP, and magnesium or manganese. Of nearly 50 metabolites tested, the enzyme is inhibited only by ATP, UTP, citrate, and malate, and activated by AMP, GMP, and fumarate. The inhibition by citrate and ATP is not due to metal chelat...

At least two types of pyruvate kinase (ATPpyruvate phosphotransferase, EC 2.7.1.40) have been identified in rat liver, which were named type L (liver) and type M (muscle) on the basis of their immunological properties (Tanaka, Harano, Morimura & Mori, 1965). The L-type enzyme is allosterically activated by fructose 1,6-diphosphate (Taylor & Bailey, 1967) and is subject to hormonal and dietary c...

The kinetic properties of purified yeast pyruvate kinase were investigated. The enzyme showed cooperative kinetics toward the essential activating monovalent cations K+ and NH4+, Mg2+, and phosphoenolpyruvate. Fructose 1,6diphosphate, which yielded homotropic cooperative kinetics and did not affect maximal velocity, transformed the sigmoidal kinetics of Kf and NH4+, Mgz+, and phosphoenolpyruvat...

The specific activity of Coprinus lagopus pyruvate kinase is high under conditions of glycolysis but low under conditions of gluconeogenesis. Only a single form of the enzyme was detectable, the properties of which resemble in a number of respects those of the allosteric forms of pyruvate kinase. These properties include co-operative interactions with phosphoenolpyruvate (PEP), ATP and fructose...