AndrewAlexanderSandbox1: Difference between revisions
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This reaction, although appearing reversible, is essentially irreversible under physiological conditions, thus helping control the metabolic flux in glycolysis. Through allosteric regulation, the PEP binding site is | This reaction, although appearing reversible, is essentially irreversible under physiological conditions, thus helping control the metabolic flux in glycolysis. Through allosteric regulation, the PEP binding site is distorted by 29 degrees on transition from the R-state to the T-state. | ||
Pyruvate kinase is primarily allosterically regulated <ref>PMID:8682196 </ref>. | Pyruvate kinase is primarily allosterically regulated <ref>PMID:8682196 </ref>. | ||
Allosteric regulation of enzyme activity is a mechanism for finely tuning biochemical reaction pathways in order to maintain an appropriate balance of intracellular substrate and product concentrations. Allosteric processes also allow an enzyme's activity to be coordinated with other cellular reactions and signaling pathways.Through site directed mutagenisis studies, Lys382 is suggested to be involved in both activator binding and in the allosteric transition mechanism. These domain interfaces are critical for the trasnition. Tey couple changes in the tertiary and quaternary structures in fructose 1,6 biphosphate binding sites for pyruvate kinase. | Allosteric regulation of enzyme activity is a mechanism for finely tuning biochemical reaction pathways in order to maintain an appropriate balance of intracellular substrate and product concentrations. Allosteric processes also allow an enzyme's activity to be coordinated with other cellular reactions and signaling pathways.Through site directed mutagenisis studies, Lys382 is suggested to be involved in both activator binding and in the allosteric transition mechanism. These domain interfaces are critical for the trasnition. Tey couple changes in the tertiary and quaternary structures in fructose 1,6 biphosphate binding sites for pyruvate kinase. | ||
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Without a high K+ | Without a high K+ concentration, the kinetic mechanism of pyruvate kinase changes from random to ordered with phosphoenolpyruvate as the first substrate. Vmax with K+ was about 400 times higher than a wild type sample without K+. In the presence of K+, the affinities for phosphoenolpruvate and ADP were 2-6 times higher than in the abscence of K+. This shows that K+ is involved in the acquisition of the active conformation of the enzyme, allowing either phosphoenolpyruvate or ADP to bind independently, but without K+, ADP cannot bind to the enzyme until phosphoenolpyruvate forms a competent active site for an ordered mechanism. Wild type pyruvate kinase without K+ has an ordered rapid equilibrium kinetic mechanism that shows Vmax to be 0.8 +/- -.04 umol/min mg with a kcat of 3.2 s^-1. When the wild-type pyruvate kinase has K+, it is in a random rapid equilibrium kinetic mechanism with a Vmax of 299 +/- 11 umol/min mg with a kcat of 1182 <ref>PMID:16147999</ref>. | ||
As indicated earlier, phosphoenolpyruvate can enhance the activity of the reaction by adding into the enzyme because it is the rate limiting step. The enzyme follows hyperbolic kinetics. Experiments found that no incorporation was found in the reaction, indicating a random, rapid dissociation of the products. This, then, assumes that the products inhibit the enzyme’s reaction by simply reversing the reaction. Both pyruvate and ATP have been shown to be non-competitive inhibitors of pyruvate kinase <ref>PMID:629752</ref>. | As indicated earlier, phosphoenolpyruvate can enhance the activity of the reaction by adding into the enzyme because it is the rate limiting step. The enzyme follows hyperbolic kinetics. Experiments found that no incorporation was found in the reaction, indicating a random, rapid dissociation of the products. This, then, assumes that the products inhibit the enzyme’s reaction by simply reversing the reaction. Both pyruvate and ATP have been shown to be non-competitive inhibitors of pyruvate kinase <ref>PMID:629752</ref>. | ||
