Desribe how the protein phosphatase-1 (PP1) in the liver is regulated and how glucose allosterically regulates...

Desribe how the protein phosphatase-1 (PP1) in the liver is regulated and how glucose allosterically regulates glycogen phosphorylase in the liver.

Expert Solution

Protein phosphatase 1 (PP1) is a major eukaryotic serine/threonine protein phosphatase enzyme. It has a major role in the regulation of cell cycle progression, protein synthesis, muscle contraction, carbohydrate metabolism, transcription, and neuronal signaling.

The catalytic subunit of PP1 is regulated by the heat-stable protein inhibitor-1, and inhibitor-2.

Phosphorylation of inhibitor-1 by cAMP-dependent protein kinase is required for PP1 inhibition. In contrast, unphosphorylated inhibitor-2 interacts with the PP1 catalytic subunit, and leads to the inhibition of enzymatic activity and, subsequently, to the formation of an inactive complex termed Mg-ATP-dependent phosphatase.

Insulin secreted in response to hyperglycemia reduces glycogenolysis by enhancing the action of Protein phosphatase 1 which inactivates glycogen phosphorylase.

How glucose allosterically regulates glycogen phosphorylase in the liver is by means of inhibition and activation on the enzyme. A rise in blood glucose after a meal inhibits glycogenolysis.And a fall in blood glucose between the meals or during starvation enhances glycogenolysis.

gladiator answered 1 year ago

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