AndrewAlexanderSandbox1: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
|||
| Line 20: | Line 20: | ||
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>. | 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>. | ||
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 | 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. | ||
a. Phosphoenolpyruvate, the substrate, can impact enzymatic activity by enhancing the reaction | a. Phosphoenolpyruvate, the substrate, can impact enzymatic activity by enhancing the reaction | ||
| Line 27: | Line 27: | ||
b. ATP and pyruvate have been found to be a negative allosteric inhibitor. | b. ATP and pyruvate have been found to be a negative allosteric inhibitor. | ||
c. Alanine has also been found to be a negative allosteric modulator. | 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>. | ||
