Glucagon is a hormone that signals the liver when blood suga

Glucagon is a hormone that signals the liver when blood sugar is low. For each of the following enzymes, indicate whether you would expect that glucagon would lead to (A) an increase, (B) decrease or (C) have no effect on these enzymes activity in the liver. Fructose-1, 6-bisphosphatasc A Fructose-2, 6-bisphosphatase A Phosphofructokinase-1 b Phosphofructokinasc-2 B Phosphorylase Kinase B, Glycogen phosphorylase A Glycogen synthase B Glyceraldehyde 3-phosphate dehydrogenase C Enolase C, Phosphoglycerate kinase Pyruvate kinase, Protein Phosphatase Insulin is a hormone that signals the liver when blood sugar is high. For each of the following enzymes, indicate whether you would expect that insulin would lead to (A) an increase, (B) a decrease or (C) have no effect on these enzymes activity in the liver. Fructose-l, 6-bisphosphatase B Fructose-2, 6-bisphosphatase B Phosphofructokinase Phosphofructokinase-2 A. Phosphorylase kinase, Glycogen phosphorylase Glycogen Synthase Glyceraldehyde 3-phosphate dehydrogenase C Enolase C phosphoglycerate kinase C Pyruvate kinase Protein Phosphatase A

Solution

Answer 7.

During fasting, blood sugar is low. At this time, the hormone glucagon, signals the liver to produce glucose from glycogen. This extra glucose produced is released into the blood stream. This restores the glucose lag of blood.

When blood has less glucose, glycolysis will be slowed down. So, enzymes of glycolysis will be reduced.

Fructose 1, 6 bis-phosphatase and Fructose 2, 6 bis-phosphatase convert fructose 1, 6 and 2, 6 bisphosphate back to fructose 6, phosphate which make glucose. So, these enzymes will be elevated.

Phosphofructokinase 1 and 2 converts fructose 6 phosphate into fructose 1,6 bisphosphate. This will further enhance glycolysis. So, these enzymes will be decreased by glucagon hormone.

Phosphorylase kinase will be enhanced. When glucagon stimulates G-protein, adenylate kinase is enhanced. This produces cAMP. cAMP enhances phosphorylase kinase.

Glycogen phosphorylase is under the effect of cAMP; which is elevated by the hormone, glucagon.

Glycogen synthase results in elevation of production of glycogen. This enzyme will be reduced in the above case.

G-3-PD enhances glycolysis. So, either it will be reduced, or no effect on its production will be there.

Enolase -- This enzyme is not a regulatory enzyme. It has reversible effect. So, no effect should be there.

Phosphoglycerate kinase--- no effect.

Pyruvate kinase will be reduced. This enzyme is a glycolytic regulatory enzyme. Please note that glucagon will have inhibitory effect on all glycolytic regulatory enzymes.

Protein Phosphatase 1A, will reduced in presence of cAMP.