BIOC2000 Lecture Notes - Lecture 10: Hyperbola, Allosteric Regulation, Phosphofructokinase
Friday, 18 May, 2018
Gilam L10
Allosteric regulation of enzyme
-glycolysis Phosphofructosekinase
-Hexokinase for glycogen synthesis
-Phosphohexose isomerase for gluconeogenesis shared pathway
-unique to glycolysis: PFK effectively catalysing and it is an irreversible reaction
-PFK has a lot of regulatory mechanism
-rely on Relax R form and Tense inactive form
-4 identical monomers quaternary structure, 4 active sites, S (F6P) binds better in R
state F6P show positive cooperatitvity (1 event makes another event more likely) F6P
binds to the other shift to R form which has better affinity for F6P
-F6P binds makes binding easier since has positive coorperativity
-more F6P [S] binds rates picks up sigmoidal curve (s shape) shows more enzymes
becomes active so rate picks up
-allosterically controlled enzyme exist as dynamic conformation protein has different
conformation inactive and active conformation leading to conformity in PFK F6P
favouring R form
-Balance shifts when effective binds
-S shift to active form inhibiter (alanine to pyruvate kinase) allosteric inhibitor inhibiting
shifting to inactive conformation
-PFK shows sigmoidal curve we cannot find Km with sub sat curve still Vmax
-when n= 1 (coorperativity) shows rectangular hyperbola
-negative substrate concentration low coorperativity , n=3 high coorperativity shown)
-substrate has homotropic F6P shift binding of itself lead to s shape kinetic
-binding of other moecule alter the binding of F6P (heterotrophic)
-ATP as subtrate binding to substrate binding site, allosteric site binding favour T form
lower affinity for F6P
-Sub sat curve with ATP or F6P
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Document Summary
Unique to glycolysis: pfk effectively catalysing and it is an irreversible reaction. Pfk has a lot of regulatory mechanism. Rely on relax r form and tense inactive form. F6p binds makes binding easier since has positive coorperativity. More f6p [s] binds rates picks up sigmoidal curve (s shape) shows more enzymes becomes active so rate picks up. Allosterically controlled enzyme exist as dynamic conformation protein has different conformation inactive and active conformation leading to conformity in pfk f6p favouring r form. S shift to active form inhibiter (alanine to pyruvate kinase) allosteric inhibitor inhibiting shifting to inactive conformation. Pfk shows sigmoidal curve we cannot nd km with sub sat curve still vmax. When n= 1 (coorperativity) shows rectangular hyperbola. Negative substrate concentration low coorperativity , n=3 high coorperativity shown) Substrate has homotropic f6p shift binding of itself lead to s shape kinetic. Binding of other moecule alter the binding of f6p (heterotrophic)
