Phosphoeno/pyruvate

Elimination of water from 2-phospho-glycerate produces the phosphate ester of the enol form of pyruvate—phosphoeno/pyruvate (PEP). This reaction also raises the second phosphate residue to a high potential. 

Positions 629-655 (ice plant ppcl) have been implicated as part of the binding site for phosphoeno/pyruvate (reviewed by Andreo et al.,... 

Adams, C.A., Leung, F. Sun, S.S.M. (1986). Molecular properties of phosphoeno/pyruvate carboxylase from C3, C3-C4 intermediate, and C4 Flaveria species. Planta 167, 218-25. 

Andreo, C.S., Gonzales, D.H. Iglesias, A.A. (1987). Higher plant phosphoeno/pyruvate carboxylase. FEBS Letters 213, 1-8. 

Cretin, C., Keryer, E., Tagu, D., Lepiniec, L., Vidal, J. Gadal, P. (1990). Complete cDNA sequence of sorghum phosphoeno/pyruvate carboxylase involved in C4 photosynthesis. Nucleic Acids Research 18, 658. 

Cushman, J.C. Bohnert, H.J. (1989a). Nucleotide sequence of the Ppcl gene from M. crystallinum, encoding the CAM-form of phosphoeno/pyruvate carboxylase. Nucleic Acids Research 16, 6745-6. 

Foster, J.G., Edwards, G.E. Winter, K. (1982). Changes in the levels of phosphoeno/pyruvate carboxylase with induction of CAM in M. crystallinum L. Plant and Cell Physiology 23, 585-94. 

Fujita, N., Miwa, T., Ishijima, S., Izui, K. Katsuki, H. (1984). The primary structure of phosphoeno/pyruvate carboxylase of Escherichia coli. Nucleotide sequence of the ppc gene and deduced amino acid sequence. Journal of Biochemistry 95, 909-16. 

Hudspeth, R.L. Grula, J.W. (1989). Structure and expression of the maize gene encoding the phosphoeno/pyruvate carboxylase isozyme involved in C4 photosynthesis. Plant Molecular Biology 12, 579-89. 

Izui, K., Ishijima, S., Yamaguchi, Y., Katagiri, F., Murata, T., Shi-gesada, K., Sugiyama, T. Katsuki, H. (1986). Cloning and sequence analysis of cDNA encoding active phosphoeno/pyruvate carboxylase of the C4-pathway from maize. Nucleic Acids Research 14, 1615-28. 

Jiao, J. Chollet, R. (1990). Regulatory phosphorylation of serine-15 in maize phosphoeno/pyruvate carboxylase by a C4-leaf protein-serine kinase. Archives of Biochemistry and Biophysics 283, 300-5. 

Jiao, J., Vidal, J., Echevarria, C. Chollet, R. (1991). In vivo regulatory phosphorylation site in C4-leaf phosphoeno/pyruvate carboxylase from maize and sorghum. Plant Physiology 96, 297-301. 

Koizumi, N., Sato, F., Terano, Y. Yamada, Y. (1991). Molecular analysis of phosphoeno/pyruvate carboxylase of a C3 plant, Nicotiana tabacum. Plant Molecular Biology 17, 535-9. 

Latzko, E. Kelly, G.J. (1983). The many-faceted function of phosphoeno/pyruvate carboxylase in C3 plants. Physiologie Vegetale 21, 805-15. 

Matsuoka, M. Hata, S. (1987). Comparative studies of phosphoeno/pyruvate carboxylase from C3 and C4 plants. Plant Physiology 85, 947-51. 

Matsuoka, M. Minami, E. (1989). Complete structure of the gene for phosphoeno/pyruvate carboxylase from maize. European Journal of Biochemistry 181, 593-8. 

Nimmo, G.A., Nimmo, H.G., Hamilton, I.D., Fewson, C.A. Wilkins, M.B. (1986). Purification of the phosphorylated night form and dephosphorylated day form of phosphoeno/pyruvate carboxylase from Bryophyllum fedtschenkoi. Biochemical Journal 239, 213-20. 

O Leary, M.H. (1982). Phosphoeno/pyruvate carboxylase An enzymologists view. Annual Review of Plant Physiology 33, 297-315. 

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

Tarczynski, M.C. Outlaw, W.H. (1990). Partial characterization of guard-cell phosphoeno/pyruvate carboxylase kinetic datum collection in real time from single-cell activities. Archives of Biochemistry and Biophysics 280, 153-8. 

Vidal, J., Nguyen, J., Perrot-Rechenmann, C. Gadal, P. (1986). Phosphoeno/pyruvate carboxylase in soybean root nodules an immunochemical study. Planta 169, 198-201. 

Willmer, C.M. (1983). Phosphoeno/pyruvate carboxylase activity and stomatal operation. Physiologie Vegetale 21, 943-53. 

Gluconeogenesis uses seven of the reactions in glycolysis, but three are replaced by the sum of the pyruvate carboxylase and phosphoeno/pyruvate carboxykinase reactions, the fructose 1,6-biphosphatase reaction, and the glucose 6-phosphatase reaction. Tables 4.7, 4.8, and 4.9 give the thermodynamic properties of these reactions and the net reaction for gluconeogenesis. 

C02(g) to C02tot is smaller at higher pH and larger at lower pH. Also note that GTP and GDP have been replaced with ATP and ADP in the phosphoeno/-pyruvate carboxykinase reaction because because the correct result can be obtained in this way. 

The initial step in the C4 pathway is the carboxylation of phosphoeno/pyruvate (PEP) in the cytoplasm of the mesophyll cells. The reaction is catalysed by PEP carboxylase (Eqn. 4). 

Fig. 2. The C4 cycle of COj fixation in photosynthesis. The pathway shown is that occurring in Type-1 C4 plants such as Zea mays. Abbreviations RuBP, ribulose 1,5-bisphosphate PGA, 3-phosphogly-cerate PEP, phosphoeno/pyruvate OAA, oxaloacetate. The partial triose-P/PGA shuttle is based primarily on evidence demonstrating concentration gradients that would support metabolite flux between the two cell types.

Fig. 3. Carbon flow during Crassulacean acid metabolism (CAM). The simplifled pathway shown is that occurring in malic enzyme type plants. The location of the decarboxylation reaction is believed to be the mitochondria (NAD-malic enzyme type) or the cytosol [16] or chloroplast (NADP-malic enzyme type) [15]. Abbreviations G6P, glucose 6-phosphate F6P, fructose 6-phosphate F16P, fructose 1,6-bisphosphate GAP, glyceraldehyde 3-phosphate PEP, phosphoeno/pyruvate PYR, pyruvate.

Any method for determining the specificity is dependent upon knowledge of gaseous substrate concentrations. Generally, [O2] is maintained constant at either ambient concentration (255 p,M) or at 100% O2 saturation (1.2 mM). Free [CO2] is varied with exogenously-added NaHC03. The total concentration of all species of CO2 can be determined spectrophotometrically by the phosphoeno/pyruvate... 

The earlier flux analyses based on positional enrichment patterns did not succeed in resolving the two C3-carboxylating enzymes phosphoeno/pyruvate carboxylase (PEPCx) and pyruvate carboxylase (PyrCx) because the carbon routes in both reactions to oxaloacetate are identical and because no differences... 

Figure 22. The PTS chemotactic signal-transduction pathway. Bold black arrow, interaction between proteins red arrow, inhibitory interaction. Abbreviations El, Enzyme I Ell, Enzyme II EI R phosphorylated Enzyme I HPr R phosphorylated HPr PER phosphoeno/pyruvate S, RTS substrate S R phosphorylated PTS substrate. See text for details.

Abbreviations ERK, extracellular signal-regulated kinase GPCR, G-protein-coupled receptor MCP, methyl-accepting chemotaxis protein PIP3, phophatidylinositol triphosphate PLCy, phospholipase Cy PTS, phosphoeno/pyruvate-dependent carbohydrate phosphotransferase system. At least in the sea urchin. 

---