Pyruvate kinase

About: Pyruvate kinase is a research topic. Over the lifetime, 5683 publications have been published within this topic receiving 180020 citations. The topic is also known as: ATP:pyruvate 2-O-phosphotransferase & phosphoenolpyruvate kinase.

Effect of copper on liver key enzymes of anaerobic glucose metabolism from freshwater tropical fish Prochilodus lineatus.

Abstract: We investigated the effect of copper on liver key enzymes of the anaerobic glucose metabolism (hexokinase, HK; phosphofructokinase, PFK; pyruvate kinase, PK; lactate dehydrogenase, LDH) as well as of the pentose pathway (glycose-6-phosphate dehydrogenase, G6PDH) from the fish Prochilodus lineatus. The fish were acclimated at either 20 degrees C or 30 degrees C at pH 7.0, transferred to water at pH 4.5 or 8.0, and exposed to 96 h-CL(50) copper concentrations. Copper accumulation in liver was higher in fish acclimated at 20 degrees C and maintained in water pH 8.0. Three-way analysis of variance revealed a significant effect of temperature on all enzymes, a significant effect of pH on all enzymes except for PK, and a significant effect of copper on only PFK, and LDH in pH 4.5 at 20 degrees C and, at 30 degrees C, on PFK and PK at pH 4.5 and 8.0, HK at pH 4.5 and G6PDH at pH 8.0. There were significant interactions between treatments for many enzymes. These changes suggest that the activity of enzymes in question is modified by a change in ambient water. At least at 30 degrees C, the overall reduction in the glycolytic enzyme activities of copper-exposed fish seems to reduce energy availability via glucose metabolism, thereby contributing to enhance copper toxic effects.

Glutamine synthetase from mammalian tissues.

Abstract: Publisher Summary This chapter provides an overview of the glutamine synthetase from mammalian tissues. The glutamine synthesis reaction is freely reversible. When the enzyme is incubated with 10 m M concentrations each of L-glutamate, ammonium ions, and ATP in the presence of Mg 2+ at pH 7.0 and 37 ° , equilibrium is attained when about 90% of the L-glutamate is converted to L-glutamine. Substitution of hydroxylamine for ammonia in this system leads to a reaction that goes to greater than 99% of completion. The glutamine synthetases of mammalian origin closely resemble each other with respect to amino acid composition, subunit structure, and molecular weight. They differ substantially in these respects from bacterial glutamine synthetases, some of which exist in adenylylated forms. Glutamine synthetase activity may be followed by measuring the rate of formation of inorganic phosphate, ADP, or glutamine. ADP may be determined by coupling the glutamine synthetase reaction with those catalyzed by pyruvate kinase and lactate dehydrogenase. By use of reaction mixtures containing labeled glutamate, the disappearance of glutamate and the formation of glutamine may be determined. A commonly used procedure for determining glutamine synthetase activity involves replacement of ammonia by hydroxylamine. In this reaction, γ-glutamylhydroxamate is formed, which gives a characteristic color reaction on addition of ferric chloride.