AndrewAlexanderSandbox1: Difference between revisions

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In the glycolytic cycle, there are three compounds that have a large negative ∆G which includes the reaction pyruvate kinase catalyzes. Due to these three steps regulating the overall activity of the cycle, they are generally irreversible in vivo. Through numerous studies, the activity of pyruvate kinase has been found to be regulated by these effectors.
In the glycolytic cycle, there are three compounds that have a large negative ∆G which includes the reaction pyruvate kinase catalyzes. Due to these three steps regulating the overall activity of the cycle, they are generally irreversible in vivo. Through numerous studies, the activity of pyruvate kinase has been found to be regulated by these effectors.
Without a high K+ concnetration, 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>{{article |author=Oria-Hernandez, Jesus.; Cabrera, Nallely.|title=Pyruvate Kinase Revisited: The Activating effect of K+|volume=280|pages=37924-37929|}}</ref>.




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c. Alanine has also been found to be a negative allosteric modulator  <ref>{{article |author=Dann, Leighton G.; Britton, Hubert G.|title=Kinetics and Mechanism of Action of Muscle Pyruvate Kinase|volume=169|pages=39-54|}}</ref>.
c. Alanine has also been found to be a negative allosteric modulator  <ref>{{article |author=Dann, Leighton G.; Britton, Hubert G.|title=Kinetics and Mechanism of Action of Muscle Pyruvate Kinase|volume=169|pages=39-54|}}</ref>.


Without a high K+ concnetration, 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>{{article |author=Oria-Hernandez, Jesus.; Cabrera, Nallely.|title=Pyruvate Kinase Revisited: The Activating effect of K+|volume=280|pages=37924-37929|}}</ref>.




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