Gluconeogenesis Flashcards
The role of glucagon and epinephrine in gluconeogenesis
- inhibit glycolysis
- stimulate gluconeogenesis by increasing cAMP conc.
- > activates cAMP dependent protein kinase
- > phosphorylation and inactivation of pyruvate kinase
Location
mainly in the liver but also kidneys
Synthesis of glucose from non-carbonate compounds
- Lactate: oxidized by NAD+, catalyzed to pyruvate by lactate DH
- Amino acids: degradation of muscle proteins, converted to pyruvate and nitrogen to urea.
- Glycerol: triaglycerols react with ATP and form dihydroxyacetone phosphate
Gluconeogenesis activated by
glucagon
acidosis
glucocorticoids
Pyruvate -> Oxaloacetate
- IRREVERSIBLE
- enzyme: PYRUVATE CARBOXYLASE (requires biotin and ATP)
- mitochondrial matrix
Allosteric regulation of pyruvate carboxylase
activated by: high acetyl-CoA
Oxaloacetate -> Phosphoenolpyruvate
-IRREVERSIBLE
-decarboxylation
-enzyme: PHOSPHOENOLPYRUVATE CARBOXYKINASE
(requires GTP, inducible enzyme)
Regulation of Phosphoenolpyruvate carboxykinase
activated by: glucocorticoids, glucagon, retinoids
inhibited by: glucose and insulin
Phosphoenolpyruvate -> 2-phosphoglycerate
- reversible
- enzyme: ENOLASE
2-phosphoglycerate -> 3-phosphoglycerate
- reversible
- enzyme: PHOSPHOGLYCEROMUTASE
3-phosphoglycerate -> 1,3-bisphosphoglycerate
- reversible
- dephosphorylation of ATP
- enzyme: PHOSPHOGLYCERATE KINASE
1,3-bisphosphoglycerate -> Glyceraldehyde-3P
- reversible
- oxidation of NADH
- enzyme: GLYCERALDEHYDE-3P DEHYDROGENASE
Glyceraldehyde-3P + Dihydroxuacetone phosphate -> Fructose-1,6-bisphosphate
- reversible
- enzyme:ALDOLASE
Glycerol->Glycerol3P->Dihydroxyacetone phosphate
-enzyme: GLYCEROL KINASE
Fructose-1,6-bisphosphate -> Fructose-6P
- IRREVERSIBLE
- enzyme: FRUCTOSE-1,6-BISPHOSPHATASE
- hydration
