Phospho-Enolpyruvate Carboxykinase

The hormones glucagon, cortisol and insulin regulate the concentrations of some enzymes and hence their activities. These include glucokinase, pyruvate kinase and phospho-enolpyruvate carboxykinase. Most work has been carried out on the carboxykinase enzyme, for which it is known that glucagon and cortisol increase the concentration whereas insulin decreases it. These changes are brought about at the transcriptional level by changing the activity of transcription factors (Chapter 20). Since the hormones... 

In this patient, inhibition of phospho-enolpyruvate carboxykinase would cause... 

Associated with induction of phospho-enolpyruvate carboxykinase (PEPCK)... 

A person who accidentally ingested a compound that completely inhibited phospho-enolpyruvate carboxykinase could still form substantial amounts of blood glucose from... 

E. Both fructose and galactose can be converted to blood glucose in the absence of phospho-enolpyruvate carboxykinase, but this enzyme is required for conversion of lactate to blood glucose. Muscle glycogen is not converted to blood glucose. 

Hoppner, W., Sussmuth, W., O Brien, C., and Seitz, H. J., Cooperative effect of thyroid and glucocorticoid hormones on the induction of hepatic phospho-enolpyruvate carboxykinase in vivo and in cultured hepatocytes, Em.. Biochem., 159(2], 399, 1986. 

Under anaerobic conditions procyclic stages of T. rhodesiense are capable of utilizing glucose and glycerol, provided COj is present (8). Most of the carbon is recovered as succinate (75 and 63%, respectively) and a smaller amount of acetate (25 and 4%, respectively). Anaerobic data for T. brucei are not available. The glycosomal phospho-enolpyruvate carboxykinase (PEPCK) and malate dehydrogenase, virtually absent from bloodstream forms, but fully expressed in the procyclics, are believed to fix COj and produce succinate as an anaerobic end-product (4,10). 

Concerning gluconeogenesis, we have found that when the livers of well-fed rats are perfused in the presence of low concentrations of glucose, the activity of the phospho-enolpyruvate carboxykinase (PEPCK) increases significantly. This increase is not related to the glycogen content, and seems to be the result of de novo synthesis of the enzyme since it is prevented by prior administration of cycloheximide or actinomycin D. 

Iversen T-G, Standal R, Pederson T, Caucheron DH (1994) IS 1032 from Acetobacter xylinunty a new mobile insertion sequence. Plasmid 32 46-54 Jabalquinto AM, Laivenieks M, Zeikus JG, Cardemil E (1999) Characterization of the oxaloacetate decarboxylase and pyruvate kinase-like activities of Saccha-romyces cerevisiae and Anaerobiospirillum succiniciproducens phospho-enolpyruvate carboxykinases. J Prot Chem 18 659-664 Jarvis L (2001) Lactic acid outlook up as polylactide nears market Chem Mark Repor 259(9) 5,14... 

Podkovyrov SM, Zeikus JG (1993) Purification and characterization of phospho-enolpyruvate carboxykinase, a catabolic C02-fixing enzyme, from Anaerobiospirillum succiniciproducem. ] Gen Microbiol 139 223-228 Poehland HD, Schierz V, Schumann R (1993) Optimization of gluconic acid synthesis by removing limitations and inhibitions. Acta Biotechnol 13 257-268... 

Phosphoenolpyruvate carboxykinase converts oxaloacetate to phospho-enolpyruvate, Phosphoenolpyruvate forms fructose 1,6-bisphosphate by reversal of the steps of glycolysis. 

Cooper TG, Tchen TT, Wood HG, Benedict CR. (1968). The carboxylation of phospho-enolpyruvate and pyruvate. I. The active species of COj utilized by phosphoenolpyruvate carboxykinase, carboxytransphosphorylase, and pyruvate carboxylase. J Biol Chem, 243, 3857-3863. 

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