Phospho-enolpyruvate

Phenylphosphate synthase consists of three subunits with molecular masses of 70, 40, and 24kDa. Subunit 1 resembles the central part of classical phospho-enolpyruvate synthase which contains a conserved histidine residue. It catalyzes the exchange of free [ C] phenol and the phenol moiety of phenylphosphate but not the phosphorylation of phenol. Phosphorylation of phenol requires subunit 1, MgATP, and another protein, subunit 2 (40kDa), which resembles the N-terminal part of phosphoenolpyruvate synthase. Subunit 1 and 2 catalyze the following reaction ... 

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... 

PFK-1 is subject to allosteric inhibition by ATP, citrate, and phospho-enolpyruvate, all of which are elevated when the cell has a high level of energy reserves. 

Another glycolytic enzyme, enolase, catalyzes the reversible dehydration of 2-phosphoglycerate to phospho-enolpyruvate ... 

As is evident from the additivity of free-energy changes of sequential reactions, any phosphoiylated compound can be synthesized by coupling the synthesis to the breakdown of another phosphoiylated compound with a more negative free energy of hydrolysis. For example, because cleavage of Pi from phospho-enolpyruvate (PEP) releases more energy than is needed to drive the condensation of Pi with ADP, the... 

FIGURE 14-19 Alternative paths from pyruvate to phospho-enolpyruvate. The path that predominates depends on the glucogenic precursor (lactate or pyruvate). The path on the right predominates when lactate is the precursor, because cytosolic NADH is generated in the lactate dehydrogenase reaction and does not have to be shuttled out of the mitochondrion (see text). The relative importance of the two pathways depends on the availability of lactate and the cytosolic requirements for NADH by gluconeogenesis. 

The third bacterial regulatory device is the phospho-enolpyruvate sugar phosphotransferase system (Eq. 8-4). It is involved not only in transport but also in controlling a variety of physiological processes.110 112 113... 

Mesophyll cells use C02 from the air to convert phospho-enolpyruvate to oxaloacetate (fig. 15.28). Oxaloacetate is reduced to malate, which then moves to the bundle sheath cells that surround the vascular structures in the interior of the leaf. Here malate is decarboxylated to pyruvate in an oxidative reaction that reduces NADP+ to NADPH. The pyruvate returns to the mesophyll cells, where it is phos-phorylated to phosphoenolpyruvate. This phosphorylation is driven by splitting of ATP to AMP and pyrophosphate and subsequent hydrolysis of the pyrophosphate to phosphate. 

Enolase catalyzes the dehydration of 2-phosphoglycerate to form phospho-enolpyruvate (PEP). This reaction converts the low-energy phosphate ester bond of 2-phosphoglycerate into the high-energy phosphate bond of PEP. 

Answer In maize, C02 is fixed by the C4 pathway elucidated by Hatch and Slack. Phospho-enolpyruvate is rapidly carboxylated to oxaloacetate, some of which undergoes transamination to aspartate but most of which is reduced to malate in the mesophyll cells. Only after subsequent decarboxylation of labeled malate does 14C02 enter the Calvin cycle for conversion to glucose. The rate of entry into the cycle is limited by the rate of the rubisco-catalyzed reaction. 

Pyruvate kinase catalyzes the conversion of phospho-enolpyruvate and ADP to pyruvate and ATP. A proton is taken up in the reaction. The enzyme binds one K+ and two Mg + ions. The 2.9 A crystal structme shows that the K+ interacts directly with the migrating phosphoryl group and indirectly with residues in the active site. Activity with Na+ is about 9% that of K+. Figme 1 shows the geometry of the active site. Oxalyl phosphate is a substrate for pyruvate... 

The glycolysis pathway shown in Figure 29.4 has a number of intermediates that contain phosphate group. . Why can 3-phosphoglyceroyl phosphate and phospho-enolpyruvate transfer a phosphate group to ADP while glucose 6-phosphate cannot ... 

ADP can accept phosphate groups from compounds such as phospho-enolpyruvate, phosphocreatine, or 1,3-bisphosphoglycerate, forming ATP. 

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

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. 

In order to enhance affinity and selectivity for Brc-Abl, we modified the inhibitor methylating at positions I and II (Fig. 7.5d). The synthesis of the wrapping prototype recapitulates imatinib synthesis [38], as described in [39], To test whether the specificity and affinity for Brc-Abl improved, we conducted a spectrophotometric kinetic assay to measure the phosphorylation rate of peptide substrates in the presence of the kinase inhibitor at different concentrations. This assay couples production of adenosine diphosphate (ADP), the byproduct of downstream phosphorylation, with the concurrent detectable oxidation of reduced nicotinamide adenosine dinucleotide (NADH). The oxidation results upon transfer of phosphate from PEP (phospho-enolpyruvate) to ADP followed by the NADH-mediated reduction of PEP to lactate. Thus, phosphorylation activity is monitored by the decrease in 340 nm absorbance due to the oxidative conversion NADH->-NAD+ [34, 39]. 

FIGURE 5.5 The coupled reaction in which ATP supplies the phosphoryl group for glucose-6-phosphate synthesis in contrast, phospho-enolpyruvate has a phosphoryl transfer potential sufficiently elevated to enable it to donate its phosphoryl group to ADP, generating ATP. 

Larsen, T. M., Wedeking, J. E., Rayment, I., Reed, G. H. (1996). A carboxylate oxygen of the substrate bridges the magnesium ions at the active site of enolase structure of the yeast enzyme complexed with the equilibrium mixture of 2-phosphoglycerate and phospho-enolpyruvate at 1.8 A Resolution. Biochemistry, 30, 4349—4358. 

A second mechanism of protection from caries is the incorporation of fluoride into bacterial biofilms where it inhibits enolase. Enolase catalyzes the production of phospho-enolpyruvate, the precursor of lactate in glycolysis, from 2-phosphoglycerate during glycolysis (Fig. 16.7 - see also Fig. 1.7). In addition, oral bacterial uptake of mono- and disaccharides mostly utilizes the phosphoenolpyruvate transport system to transfer them into the cytosol (Sect. 15.2.2). Fluoride therefore inhibits not only lactic acid production, but also the phosphoenolpyruvate transport system-mediated uptake of saccharide substrates. In short, fluoride inhibits saccharolytic fermentation by many oral bacteria. 

High potential. What is the equilibrium ratio of phospho-enolpyruvate to pyruvate under standard conditions when... 

Which of the following events occurs during formation of phospho-enolpyruvate from pyruvate during gluconeogenesis ... 

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