Phosphoenolpyruvate carboxylase

Gene symbols are according to those of E. coli. (173). Abbreviations Horn, Homoserine Ant, Anthranilic acid PR, Phosphoribosyl ppc, Phosphoenolpyruvate carboxylase PRDH, prephenate dehydrogenase. 

Groenhof, A.C., Bryant, J.A. Etherington, J.R. (1988). Photosynthetic changes in the inducible CAM plant Sedum telephium L. following the imposition of water stress. II. Changes in the activity of phosphoenolpyruvate carboxylase. Annals of Botany, 62, 187-92. 

Harpster, M.H. Taylor, W.C. (1986). Maize phosphoenolpyruvate carboxylases. Cloning and characterization of mRNAs encoding isozymic forms. Journal of Biological Chemistry, 261, 6132-6. 

Ostrem, J.A., Olson, S.W., Schmitt, J.M. Bohnert, H.J. (1987). Salt stress increases the level of translatable mRNA for phosphoenolpyruvate carboxylase in Mesembryanthemum crystallinum. Plant Physiology, 84,1270-5. 

Nonphotosynthetic COi fixation via phosphoenolpyruvate carboxylase (PEPC) can contribute a substantial proportion of carbon (>30%) for the biosynthesis of carboxylates in roots of P-deficient plants (Fig. 5) (11,82,101,111-113). Thus, PEPC-mediated COi fixation may be interpreted as an anaplerotic carbon... 

This enzyme, similar to all C02 assimilating enzymes, contains biotin for a cofactor. Oxaloacetate is released from the mitochondria into the cytoplasm to enter gluconeogenesis. In the cytoplasm, oxaloacetate converts to phosphoenolpyruvate via a reaction catalyzed by phosphoenolpyruvate carboxylase ... 

Bio-Research Products Inc., was founded in 1975, and specialized in the isolation, purification and characterization of enzymes and proteins. The company is well known for its production of wheat germ phosphoenolpyruvate carboxylase (PEPC). Currently, it is involved in finished goods and raw material production, through a biomedical contract. Bio-Research Products runs custom services on enzymes, proteins production, diagnostic assays, and other goods for industry, governments, or academia. Bio-Research Products, Inc. also markets a number of enzymes and associated products, and carries out custom synthesis projects. 

In addition to the aforementioned allenic steroids, prostaglandins, amino acids and nucleoside analogs, a number of other functionalized allenes have been employed (albeit with limited success) in enzyme inhibition (Scheme 18.56) [154-159]. Thus, the 7-vinylidenecephalosporin 164 and related allenes did not show the expected activity as inhibitors of human leukocyte elastase, but a weak inhibition of porcine pancreas elastase [156], Similarly disappointing were the immunosuppressive activity of the allenic mycophenolic acid derivative 165 [157] and the inhibition of 12-lipoxygenase by the carboxylic acid 166 [158]. In contrast, the carboxyallenyl phosphate 167 turned out to be a potent inhibitor of phosphoenolpyruvate carboxylase and pyruvate kinase [159]. Hydrolysis of this allenic phosphate probably leads to 2-oxobut-3-enoate, which then undergoes an irreversible Michael addition with suitable nucleophilic side chains of the enzyme. 

A problem for gluconeogenesis is that pyruvate carboxylase, which produces oxaloacetate from pyravate, is present in the mitochondria but phosphoenolpyruvate carboxylase, at least in human liver, is present in the cytosol. For reasons given in Chapter 9, oxaloacetate cannot cross the mitochondrial membrane and so a transporter is not present in any cells. Hence, oxaloacetate is converted to phosphoenolpyruvate which is transported across the membrane (Figure 6.25). 

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. 

This enzyme [EC 4.1.1.38] (also known as phosphoenolpyruvate carboxytransphosphorylase, phosphopyruvate carboxylase, and phosphoenolpyruvate carboxylase) catalyzes the reaction of phosphoenolpyruvate with orthophosphate and carbon dioxide to produce oxaloacetate and pyrophosphate (or diphosphate). The enzyme also catalyzes the reaction of phosphoenolpyruvate with orthophosphate to produce pyruvate and pyrophosphate. 

Muscolo, A., Panuccio, M. R., Abenavoli, M. R., Concheri, G, and Nardi, S. (1996). Effect of molecular complexity and acidity of earthworm faeces humic fractions on glutamate dehydrogenase, glutamine synthetase and phosphoenolpyruvate carboxylase in Daucus carota II cells. Biol. Fertil. Soils 22, 83-88. 

Obviously, discrepancies in observed enzyme responses may also result from differences in concentration of the active free metal in the direct environment of the enzyme. Phosphoenolpyruvate carboxylase (EC 4.1.1.31) for instance, which is extremely sensitive to in-vitro zinc application, was also inhibited in intact 7 day old Zea mays seedlings, treated with very high amounts of zinc (Stiborova etai., 1988). In Phaseolus vulgaris grown on a substrate containing toxic amounts of zinc, on the contrary, the same enzyme showed a significant capacity increase as compared to the control (Clijsters et al., 1984). 

In these C4 plants, the enzyme phosphoenolpyruvate carboxylase first converts CO2 to oxaloacetate. 

Dubost, G. and Gendraud, M., Activite phosphoenolpyruvate carboxylase dans les parenchymes de tubercules de Topinambour dormants ou non dormants relation avec le pH intracellulaire, C. R. Acad. Sci. Paris, 305, 619-622, 1987. 

In phosphoenolpyruvate carboxylase, structural analysis indicates the arrangement of the total 40 helices around the active site in the /la-barrel core structure [54], The additional domains create a binding site for aspartate, an allosteric inhibitor of the enzyme. Furthermore, the highly conserved hydrophobic C-terminal extension of the enzyme presumably is critical for oligomerization. 

Kabata-Pendias A (2002) A current issue of biogeochemistry of trace elements. Heavy metals, radionuclides and elements -biophytes in the environment. Semipalatinsk, 34 1 Kabata-Pendias A, Pendias H (1984) Trace elements in soils and plants. CRC Press, Boca Raton, FL Kai Y, Matsumura H, Izui K (2003) Phosphoenolpyruvate carboxylase three-dimensional structure and molecular mechanisms. Arch Biochem Biophys 414 170-179 Kaim W, Schwederski B (1993) Bioanorganische Chemie. Teubner, Stuttgart... 

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