Lecture 27: Hormonal Regulation of Metabolism Flashcards
Glucagon
-peptide hormone produced by a-cells of pancreas
-released when blood sugar DROPS
-raises concentration of glucose and fat in blood stream
Glucagon signaling pathway
-binds to GPCR glucagon receptor
-activates GS (adenylate cyclase stimulator)
Cyclic AMP
-SECOND MESSENGER
-produced from ATP by ADENYLATE CYCLASE
-hydrolyzed by phosphodiesterase
Cyclic AMP activates:
-cAMP-dependent protein kinase
-protein kinase A
cAMP mechanism
-binds to inactive PKA and forms complex
-releases active subunits
6-phosphofructo-2-kinase/ fructose2,6bisphosphatase
-bifunctional enzyme
-kinase and phosphatase activity
-controls concentration of fructose26bisphosphate
F2,6-BP activates
-kinase
-GLYCOLYSIS
F26BP suppresses
-phosphatase
-GLUCONEOGENESIS
kinase/phosphatase enzyme in liver
-converted from kinase to PHOSPHATASE by protein kinase A in response to GLUCAGON or EPINEPHRINE
-DECREASES F2,6BP and GLYCOLYSIS
-INCREASES gluconeogenesis
Liver releases glucose to the blood stream in response to:
-glucagon
-epinephrine
kinase/phosphatase enzyme in heart
-phosphatase to KINASE by protein kinase A
-different isoenzyme from liver
-responds to epinephrine
-INCREASES glycolysis
Pyruvate kinase
-inactivated in liver by protein kinase A
-PEP is used for gluconeogensis instead of converting to pyruvate
Induction of gluconeogenic enzymes in liver
-long-term effects on metabolism
-PKA phosphorylates CREB
-CREB binds to CRE
=gene expression
CRE(B)
cAMP response element (binding protein)
-CRE acts within regulatory region of genes
genes responsive to cAMP
-PEP carboxykinase
-F1,6BPase
-G6Pase