Regulation of Carbohydrate Metabolism Problem Set
Question 3: PFK-1 Regulation in Liver
Correct!
Given that the phosphofructokinase-1 (PFK-1) enzyme is regulated by insulin, but not via (de)phosphorylation, how is this regulation accomplished?
A.
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Via increased transcription of the gene encoding this enzyme
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B.
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By recruitment of pre-existing enzyme from the Golgi
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C.
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Via allosteric regulation by fructose-2,6-bisphosphatase
Activation of PFK-1 in liver is indirect, and occurs as follows: dephosphorylation of the bifunctional PFK-2/Fructose-bis phosphatase enzyme places this enzyme in the PFK-2 mode, producing fructose-2,3-bisP, which then allosterically activates PFK-1 (the tutorial for this question provides a diagram of this). A bit complicated, but when placed in the context of insulin�s role to promote glucose utilization/storage, it fits nicely into the big picture.
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D.
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Activation by association with IRS-1
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E.
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An inhibitory subunit of the enzyme dissociates after binding cAMP
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The University of Arizona
March 16, 2000
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