Cassady sandbox1: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 3: | Line 3: | ||
==Role in Glycolysis== | ==Role in Glycolysis== | ||
Glycolysis is the process for preparing, and breaking down, glucose to make pyruvic acid, which is used in anaerobic respiration or as one of the starting reactants in the citric acid cycle. | Glycolysis is the process for preparing, and breaking down, glucose to make pyruvic acid, which is used in anaerobic respiration or as one of the starting reactants in the citric acid cycle. After glucose has been phosphorylated and isomerized to Fructose-6-phospate, PFK begins its work. It phosphorylates the hydroxy group at the number one carbon, which in glucose was impossible. This second phosphorylation by PFK is important because it makes a doubly-high-energy compound. High energy compounds, like Fructose-6-phosphate and Fructose-1,6-bisphosphate, help to drive the endergonic processes of glycolysis through their own exergonic breakdown.<ref>Voet, Donald, Judith G. Voet, and Charlotte W. Pratt. Fundamentals of Biochemistry: Life at the Molecular Level. Hoboken, NJ: Wiley, 2008. Print.</ref>. It is important than that PFK makes a bisphosphate compound, beacause eventually that molecule will be cut in half. Thus, after the action of PFK, the six carbon compound can be broken into two high-energy three carbon compounds, which are both ready to move onto the next steps of glycolysis. | ||
==Structure== | ==Structure== | ||
| Line 9: | Line 10: | ||
==Mechanism and Regulation of Phosphofructokinase== | ==Mechanism and Regulation of Phosphofructokinase== | ||
Phosphofructokinase binds both Mg2+-ATP and fructose-6-phosphate (F6P) to make fructose-1,6-bisphosphate and Mg2+-ADP. Although the image with both of these products has not been determined, <scene name='Zach_Westrick_Sandbox/Products_2/2'>F6P and Mg2+-ADP</scene> bound to the enzyme has been. There are three ligand binding sites per subunit. Two make up the active site, which binds F6P and ATP, while the third is an allosteric binding site.<ref>PMID:6115424</ref> Some proposed residues involved at the active site include <scene name='Zach_Westrick_Sandbox/Active_site_2/1'>ASP 127 and ARG 171</scene>.<ref>http://www.nature.com/nature/journal/v327/n6121/abs/327437a0.html</ref> PFK exist in two conformational states, both <scene name='Zach_Westrick_Sandbox/R_state/1'>R</scene> and <scene name='Zach_Westrick_Sandbox/T_state/1'>T states</scene> which are in equilibrium. ATP binds both active and allosteric sites in both conformations. While ATP binds the active site equally well, it preferentially binds the allosteric site of the T state <ref>Voet, Donald, Judith G. Voet, and Charlotte W. Pratt. Fundamentals of Biochemistry: Life at the Molecular Level. Hoboken, NJ: Wiley, 2008. Print.</ref> This preferential binding causes a shift from equilibrium of the two states, to a greater amount of T state <ref>PubMed:2136935</ref>, which decreases the affinity for F6P. Allosteric activator <scene name='Zach_Westrick_Sandbox/Allosteric_activator/2'>ADP</scene> also binds to allosteric site to increase the ratio of R state phosphofructokinase. Along with ADP,AMP and F2,6P inhibit the regulatory role of ATP. | Phosphofructokinase binds both Mg2+-ATP and fructose-6-phosphate (F6P) to make fructose-1,6-bisphosphate and Mg2+-ADP. Although the image with both of these products has not been determined, <scene name='Zach_Westrick_Sandbox/Products_2/2'>F6P and Mg2+-ADP</scene> bound to the enzyme has been. There are three ligand binding sites per subunit. Two make up the active site, which binds F6P and ATP, while the third is an allosteric binding site.<ref>PMID:6115424</ref> Some proposed residues involved at the active site include <scene name='Zach_Westrick_Sandbox/Active_site_2/1'>ASP 127 and ARG 171</scene>.<ref>http://www.nature.com/nature/journal/v327/n6121/abs/327437a0.html</ref> PFK exist in two conformational states, both <scene name='Zach_Westrick_Sandbox/R_state/1'>R</scene> and <scene name='Zach_Westrick_Sandbox/T_state/1'>T states</scene> which are in equilibrium. ATP binds both active and allosteric sites in both conformations. While ATP binds the active site equally well, it preferentially binds the allosteric site of the T state <ref>Voet, Donald, Judith G. Voet, and Charlotte W. Pratt. Fundamentals of Biochemistry: Life at the Molecular Level. Hoboken, NJ: Wiley, 2008. Print.</ref> This preferential binding causes a shift from equilibrium of the two states, to a greater amount of T state <ref>PubMed:2136935</ref>, which decreases the affinity for F6P. Allosteric activator <scene name='Zach_Westrick_Sandbox/Allosteric_activator/2'>ADP</scene> also binds to allosteric site to increase the ratio of R state phosphofructokinase. Along with ADP,AMP and F2,6P inhibit the regulatory role of ATP. Three points in the process of glycolysis occur with a large negative free energy and are therefore, irreversible. These three points are hexokinase, phosphofructokinase, and pyruvate kinase; of these three PFK is considered the major regulatory point for glycolysis in muscle with a ΔG= -25.9 kJ/mol. <ref>Voet, Donald, Judith G. Voet, and Charlotte W. Pratt. Fundamentals of Biochemistry: Life at the Molecular Level. Hoboken, NJ: Wiley, 2008. Print.</ref> | ||
The PFK's Km for ATP is .020mM and .032mM.<ref>PMID: 6233271</ref> | The PFK's Km for ATP is .020mM and .032mM.<ref>PMID: 6233271</ref> | ||
