Phosphoenolpyruvate carboxykinase PEPCK

Phosphoenolpyruvate carboxykinase (PEPCK) deficiency is distinctly rare and even more devastating clinically than deficiencies of glucose-6-phosphatase or fructose-1,6-bisphosphatase. PEPCK activity is almost equally distributed between a cytosolic form and a mitochondrial form. These two forms have similar molecular weights but differ by their kinetic and immunochemical properties. The cytosolic activity is responsive to fasting and various hormonal stimuli. Hypoglycemia is severe and intractable in the absence of PEPCK [12]. A young child with cytosolic PEPCK deficiency had severe cerebral atrophy, optic atrophy and fatty infiltration of liver and kidney. 

Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes a critical reaction in gluconeogenesis, which under many conditions is the rate-limiting step in the pathway. A cAlVfP response element (CRE) and a glucocorticoid response element (GRE) are each located upstream from the transcription start site. 

Phosphorylation of gene regulatory proteins such as CREB to control gene expression, usually over several hours. The typical result is to add more enzyme to the cell. CREB induces the phosphoenolpyruvate carboxykinase (PEPCK) gene. 

Phosphoenolpyruvate carboxykinase (PEPCK) in the cytoplasm is induced by glucagon and cortisol. It converts OAA to phosphoenolpyruvate (PEP) in a reaction that requires GTP. PEP continues in the pathway to fructose 1,6-bisphosphate. 

Phosphoenolpyruvate (PEP) 510, 510s, 685s key metabolic intermediate 705, 706 as stabilized enol 697 Phosphoenolpyruvate carboxykinase 549 Phosphoenolpyruvate carboxykinase (PEPCK) 706... 

Most cestodes which have been investigated, however, conform to the second category, type 2, which is characterised by a C02-fixation step. Carbohydrate is degraded to the level of PEP by glycolysis, the steps involved being similar to those in mammalian tissue. At this point, the enzymes pyruvate kinase and phosphoenolpyruvate carboxykinase (PEPCK) compete for available substrate and a branch-point occurs (Fig. 5.4). The relative activities of these two enzymes determine the fate of the PEP and the subsequent types and amounts of end-products formed (see below). 

Hadziosmanovic, A. Kravica, S. (1982). [The activity of phosphoenolpyruvate carboxykinase (PEPCK.) and pyruvate kinase (PK) in some parasitic helminths.] In Russian. Veterinarski Arkiv, 52 55-63. [HA/52/1493]... 

Pyruvate carboxylase is followed by the Phosphoenolpyruvate carboxykinase (PEPCK) reaction. In this reaction oxaloacetate is decarboxylated with a simultaneous phosphorylation by GTP to give GDP ... 

Park, E. A., Song, S., Olive, M., and Roesler, W. J. (1997). CCAAT-enhancer-binding protein a (C/EBPa) is required for the thyroid hormone but not the retinoic acid induction of phosphoenolpyruvate carboxykinase (PEPCK) gene transcription. Biochem. J. 322,343-349. 

In addition to providing amino acids and glycerol as carbon sources, glucocorticoids promote gluconeogenesis by inducing synthesis of the enzyme phosphoenolpyruvate carboxykinase (PEPCK). 

Insulin inhibits transcription of the enzyme phosphoenolpyruvate carboxykinase (PEPCK). PEPCK is a key enzyme in gluconeogenesis and transcription is the primary means of regulating it. By inhibiting PEPCK transcription, insulin can depress glucose production tremendously. (Conversely, the hormone glucagon, which increases blood glucose levels, stimulates PEPCK transcription.)... 

Phosphoenolpyruvate carboxykinase (PEPCK) - This enzyme has no known allosteric regulators. The enzyme is controlled by hormonal regulation of its synthesis. The hormone, glucagon, activates transcription of the structural gene for the enzyme. Insulin, on the other hand, inhibits transcription of the gene. 

Pyruvate kinase (note on isozymes) 1. Pyruvate Carboxylase 2. Phosphoenolpyruvate carboxykinase (PEPCK)... 

The CO2 that was added to pyruvate to form oxaloacetate is released in the reaction catalyzed by phosphoenolpyruvate carboxykinase (PEPCK), which generates PEP (Fig. 31.7A). For this reaction, GTP provides a source of energy as well as the phosphate group of PEP. Pyruvate carboxylase is found in mitochondria. In various species, PEPCK is located either in the cytosol or in mitochondria, or it is distributed between these two compartments. In humans, the enzyme is distributed about equally in each compartment. 

The number of different lyases reported to interact with or utilize Mn(II) are relatively few. Nevertheless, those that do are important in cell metabolism and regulation. Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes... 

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