FOSFOENOLPIRUVATO CARBOXILASA PDF

FosfoenolPiruvato. AH Universidad del mar. La enzima fosfoenolpiruvato carboxilasa. Fecha de consulta: 13/Noviembre/ Consultado. En este trabajo, investigamos la compleja regulación alostérica de la formas no fosforiladas de las isoenzimas fotosintéticas de la fosfoenolpiruvato carboxilasa. Acetil-CoA = acetil-coenzima A, MDH = malato deshidrogenasa, OAA = oxalacetato, PEP = fosfoenolpiruvato, PEPC = fosfoenolpiruvato carboxilasa piruvato y.

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The same solution was always obtained after repeated submissions of the data to this server. It has been propoosed that one of the functions of the enzyme phosphoenolpyruvate carboxylase PEPCase in the roots of white lupines consists in providing the carbon required to support the significant quantity of citrate that is excreted by P-starved plants. These findings suggest that the binding of Glc6P is not affected by the binding of the inhibitor to this enzyme.

Phosphoenolpyruvate carboxylase assay and kinetic studies.

Activation carboxilasw Gly helps in increasing the flux through the C4 pathway by effectively counteracting the inhibitory effects of malate, and, therefore, it helps in increasing the concentrations of Fosfoenolpiruvat in the bundle sheet cells thus overcoming photorespiration.

Gly has been found to be much more effective than Glc6P in this respect under conditions close to those existing in vivo during the light period [14]. Rates in the absence of PEP were negligible.

Fully expanded leaves were used for the experiments. Also, because regulation of PEPC activity by metabolite effectors is mostly exerted at subsaturating concentrations of substrate [21], in the studies with the allosteric effectors we used a fixed total PEP tPEP concentration of only 0.

Introduction In leaves of C4 plants the initial reaction in the assimilation pathway of atmospheric CO 2 is the essentially irreversible carboxylation of phospho eno lpyruvate PEP by phospho eno lpyruvate carboxylase orthophosphate: Data analysis Kinetic data were analyzed by nonlinear regression calculations using a commercial computing program formulated with the algorithm of Marquardt [35].

The bicarbonate concentration in an assay medium in contact with air at pH 7. Both types of isoenzymes also differ in their affinity for the substrate PEP, the activator Glc6P and the inhibitor malate. Although the S 0.

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Photorespiration surely follows the buildup of malate during the day because of a decrease of the C4 cycle flux, a decrease cqrboxilasa to both PEPC inhibition by the increased malate concentration and depletion of the available CO 2 by a very active Calvin cycle.

Nature, Neutral amino acids concentrations, particularly that of Gly, increase under photorespiration conditions [15].

FosfoenolPiruvato by Ariadne Heredia on Prezi

When near physiological concentrations were used, Glc6P was very ineffective in overcoming malate inhibition [14]. The differences between the two enzymes in the degree of cooperativity in the binding of PEP in the presence of a high malate concentration are caboxilasa full agreement with their differences in malate affinity.

In this loop there are several amino acid residues that are conserved, or farboxilasa conservative substitutions, within each group of monocots or dicots enzymes, but that differ from one group to the other marked with an asterisk in Figure 3.

Amaranth Amaranthus hypochondriacus L. Plants of maize Zea mays L. While Glc6P is unable to revert the inhibition caused by a physiological concentration of malate, Gly can produce an enzyme almost as active than that in the absence of the inhibitor [14].

All other chemicals of analytical grade were from standard suppliers.

carboxilasa

Citrate release and activity of phosphoenolpyruvate carboxylase in roots of white lupin in response to varying phosphorus supply. As a consequence of this, D and K in the maize enzyme model are not as well positioned to bind the activator molecule as they are in the amaranth enzyme model, as indicated by a rigid docking of the Gly molecule in this site not shown fosfoenolpirvuato, which is consistent with the A 0.

Therefore, the two kinds of activators act as metabolic signals that indicate the necessity of increasing the flux through the Fosfoennolpiruvato cycle, in order to keep pace with the flux rate of the Calvin cycle in the case of Glc6P, or to increase the supply of CO 2 to the bundle sheath cells to prevent photorespiration, in the case of Gly. The concentration of phosphorylated sugars increases when the Calvin cycle is active.

Initial velocity data depending upon varied concentration of substrate were fitted to a Hill equation equation 1: In the experiments in which the concentration of the activator was varied at constant concentration of substrates, equation 2 was used: Progressive multiple sequence alignment was carried out with the ClustalX package [38], using penalties based on secondary structure.

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Term Bank – carboxilasa – Spanish English Dictionary

Protein was measured by the method of Bradford [33], using bovine serum albumin as the standard. Accepted June 8, Sequence alignments and homology model building.

The best fits were determined by the relative fit error, error of the constants and absence of significant correlation between the residuals, and other relevant variables like observed velocities, substrate concentration and data number.

The allosteric transition would not occur in the amaranth enzyme, thus accounting for the huge differences between the amaranth and the maize enzymes in their degree of activation achieved at saturation by Gly.

In leaves of C4 plants the initial reaction in the assimilation pathway of atmospheric CO 2 is the essentially irreversible carboxylation of phospho eno lpyruvate PEP by phospho eno lpyruvate carboxylase orthophosphate: When the concentration of inhibitor was varied at constant concentration of substrates, the experimental data were fitted to equation 3: Kinetic data were analyzed by nonlinear regression calculations using a commercial computing program formulated with the algorithm of Marquardt [35].

To demonstrate that citrate excretion by roots is an event more sensitive to P concentration than PEPCase, the activity of the enzyme extracted from roots of white lupines growing in soil as well as its activity and citrate release in plants growing in a nutrient solution were measured. The reaction was started by addition of the enzyme preparation.

Once the levels of malate are high, saturation of the Glc6P allosteric site would give only a marginal advantage. A rigid docking of glycine in this position not shown suggested the feasibility of binding of the activator to these residues, as we propose.