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
Glucagon suppresses the expression of
-glucokinase
-6-phosphofructo-1-kinase
-pyruvate kinase
Glycogen breakdown in liver is stimulated by
-glucagon and epinephrine
Glycogen breakdown in liver
-protein kinase A activates glycogen phosphorylase and inactivates glycogen synthase
-PKA also suppresses glycolysis in liver so glucose is released to blood stream
protein kinase A method of action
phosphorylation
glycogen phosphorylase
breaks down glycogen to glucose-1-phosphate
Insulin
-peptide hormone
-produced by Beta cells in pancreas
-released upon RISE in blood sugar
insulin reduces
concentration of glucose in blood
insulin promotes
-glucose uptake
-glycogen synthesis
-glycolysis
-fatty acid synthesis
insulin receptor
tyrosine kinase
mechanism of insulin action
-opposes actions of glucagon and epinephrine
-activates cAMP phosphodieterase
-activates phosphoprotein phosphatase
-dephosphorylation of that one enzyme phosphatase to kinase which activates pyruvate kinase
cAMP phosphodieterase
-lowers cAMP levels
-activated by insulin
Phosphoprotein phosphatase
reverses actions of protein kinase A
Hormonal regulaiton of lipid metabolism by:
-glucagon
-insulin
Glucagon effect on lipid metabolism
-promotes fatty acid OXIDATION
-increase triacyl breakdown by phosphorylation of hormone-sensitive lipase
-suppress acetyl CoA carboxylase by phosphorylation
Insulin effect on lipid metabolism
-promotes fatty acid SYNTHESIS
-increase fatty acid synthase and acety-coA carboxylase
-activates pentose phosphate pathways
Warburg effect
-even when O2, cancer cells convert glucose to lactate
-cancer cells use glucose 200x more than normal cell
Cancer cells keep carbons in the
gluco-WORLD
-part of the metabolism map lol
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