Question

In: Biology

1.       Keeping GPCR --- G-proteins ---- Adenylyl Cyclase ----Protein kinase A ----- Glycogen metabolism pathway in...

1.       Keeping GPCR --- G-proteins ---- Adenylyl Cyclase ----Protein kinase A ----- Glycogen metabolism pathway in mind, will glucose level decrease or increase in blood in the following scenarios? Provide reasoning for your answer.

a.          G? subunit loses its activity to hydrolyze GTP.

b.         G?? subunit can not be separated from f G? subunit

c.          Phosphodiestersae is overactive

d.         PKA’s affinity is lowered for cAMP.

e.          GRK is inhibited

Solutions

Expert Solution

a. If G alpha subunit loses it's activity to hydrolyze GTP then it can't activate the cAMP producing enzyme, adenylate cyclase (AC). cAMP acts as a second messenger and it further activities Protein Kinase A (PKA). If second messenger is missing then total system remains stop. So, there will be no glycogenolysis in the cell and glucose level will be decreased in blood.

b. If G alpha beta can not be separated from G alpha subunit then G alpha subunit will not be able to activate AC. Thus second messenger cAMP will not be produced. So again the glycogenolysis remains stop in the cell and the level of glucose in blood is decreased.

c. Phosphodiesterase breaks the cAMP or cGMP second messengers. Thus when these Phosphodiesterases are over reactive in the cell the level of second messenger remains lower and the process of glycogenolysis remains stop or decreases. So, the blood glucose level is decreased.

d. Protein kinase A usually activities phosphprylase kinase (PHK), an enzyme which activates phosphprylase b and convert it to phosphprylase a. But when PKA shows lower affinity to to cAMP, the PKA will not be able to activate the phosphprylase b enzyme properly. So, the level of glycogenolysis remains lower and blood glucose level is decreased.

e. G protein coupled receptor kinase (GRK) is a enzyme which phosphorylates the G protein and inhibit it to produce further signalling pathways. When GRK is inhibibited then the GPCR constititutively activities G protein and signalling pathway remains actives. So, the glycogenolysis process remains active and the blood glucose level is increased.

gladiator answered 2 years ago
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