Phosphoenolpyruvate-carboxykinase 1

Hanson, R. W., and Reshef, L., 1997. Regulation of phosphoenolpyruvate carboxykinase (GTP) gene expression. Annual Review of Biochemistry 66 581-611. 

Step 2 of Figure 29.13 Decarboxylation and Phosphorylation Decarboxylation of oxaloacetate, a jB-keto acid, occurs by the typical retro-aldol mechanism like that in step 3 in the citric acid cycle (Figure 29.12), and phosphorylation of the resultant pyruvate enolate ion by GTP occurs concurrently to give phosphoenol-pyruvate. The reaction is catalyzed by phosphoenolpyruvate carboxykinase. 

Gene activated Lipoprotein lipase fatty acid transporter protein adipocyte fatty acid binding protein acyl-CoA synthetase malic enzyme GLUT-4 glucose transporter phosphoenolpyruvate carboxykinase... 

Phosphoenolpyruvate carboxykinase i t Glucocorticoids, glucagon, epinephrine (cAMP) Insulin Glucagon ... 

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. 

PEPCK phosphoenolpyruvate carboxykinase RGS regulators of G protein signaling... 

Fmctose-6-phosphate to phosphofructokinase (PFK) Phosphoenolpyruvate carboxykinase (PEP CK) [ bypass route] Fructose-1,6 bisphosphatase... 

Following the conversion of pyruvate into oxaloacetate, phosphoenolpyruvate carboxykinase (PEP CK) catalyses a decarboxylation to form PEP (Figure 6.42). This... 

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. 

Figure 6.25 The intracellular location of the gluconeogenic enzymes. The gluconeogenic enzymes are located in the cytosol, except for pyruvate carboxylase which is always present within the mitochondria phosphoenolpyruvate carboxykinase is cytoplasmic in some species including humans. Consequently phosphoenolpyruvate must be transported across the inner mitochondrial enzyme by a transporter molecule in order for gluconeogenesis to take place.

The pyrnvate/phosphoenolpyrnvate cycle, which involves the enzymes pyrnvate kinase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase. 

Phosphoenolpyruvate carboxykinase (PEP-CK), a key enzyme in gluconeogenesis, is regulated by several hormones, all of which affect the transcription of the PEP-CK gene. Cortisol, glucagon, and thyroxin induce PEP-CK, while insulin inhibits its induction (see p. 158). 

Phosphoenolpyruvate carboxykinase (GTP) [EC 4.1.1.32], also known as phosphoenolpyruvate carboxylase and phosphopyruvate carboxylase, catalyzes the reaction of GTP with oxaloacetate to produce GDP, phosphoenolpyruvate, and carbon dioxide. ITP can replace GTP as the phosphorylating substrate. 

The glucocorticoids have important dose-related effects on carbohydrate, protein, and fat metabolism. The same effects are responsible for some of the serious adverse effects associated with their use in therapeutic doses. Glucocorticoids stimulate and are required for gluconeogenesis and glycogen synthesis in the fasting state. They stimulate phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and glycogen synthase and the release of amino acids in the course of muscle catabolism. 

Fig. 4 Speculative metabolic schemes of the main pathways in carbohydrate metabolism in Dasytricha sp. (after Ellis et al. 1991) Abbreviations AcCoA, acetyl-CoA, Hyd, hydro-genase, PEP, phosphoenolpyruvate carboxykinase, PFO, pyruvate ferredoxin oxidoreduc-tase, PYR, pyruvate, X0Xj re(j, unknown electron carrier...

The oxaloacetate is then converted to PEP by phosphoenolpyruvate carboxykinase (Fig. 14-17). This Mg2+-dependent reaction requires GTP as the phosphoryl group donor ... 

Uptake of Ca2+ into cells, or release of this ion from intracellular stores, is a major regulatory mechanism in many if not all cells (see Section E). Mn2+ activates phosphoenolpyruvate carboxykinase (Eq. 13-46) and maybe a regulator of gluconeogenesis.142 Iron controls the synthesis of ferritin and of transferrin receptors137 (Chapter 16). The specific metal ions present in many biological macromolecules are likely to participate in additional regulatory processes. 

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