Allosteric and hormonal regulation of metabolic pathways

Glycolysis and pyruvate oxidation

• Hexokinase Glucose-6-phosphate (-)
• Glucokinase (No end-product inhibition) Insulin (+)
• PFK-1 Fructose 2,6-BP, AMP (+); citrate (-) Glucagon (-)
• Pyruvate kinase Fructose 1,6-BP (+); ATP, alanine (-) Glucagon (-)
• Pyruvate dehydrogenase ADP (+); ATP, acetyl CoA, NADH (-) Insulin (+)

Citric acid cycle

Isocitrate dehydrogenase ADP (+); ATP, NADH (-)

Glycogenesis

Glycogen synthase Glucose 6-phosphate (+)

Insulin (+); glucagon in liver (-), epinephrine in muscle (-)

Gluconeogenesis

Fructose 1,6-biphosphatase Citrate (+); AMP, Fructose 2,6-BP (-) Glucagon (+)

PEP carboxykinase

Pyruvate carboxylase Acetyl CoA (+)

^ All three enzymes induced by glucagon, cortisol; suppressed by insulin

Pentose phosphate pathway

G6PD is inhibited by NADH

Fatty acid synthesis

Acetyl CoA carboxylase Citrate (+); palmitate (-) Insulin (+) Glucagon (-)

Lipolysis

Hormone sensitive lipase Epinephrine (+); insulin (-)

Beta-oxidation of fatty acids

Carnitine acyltransferase Malonyl CoA (-) *a byproduct of fatty acid synthesis, so you can't have both synthesis and beta-oxidation at the same time, futilely

Cholesterol synthesis

HMG CoA reductase Cholesterol (-) Insulin (+); glucagon (-)

Urea cycle

Carbamoyl phosphate synthetase I N-Acetylglutamate (+)

Pyrimidine synthesis

Carbamoyl phosphate synthetase II PRPP, ATP (+), UTP (-)

Purine synthesis

PRPP amidotransferase PRPP (+); IMP, AMP, GMP (-)

Heme synthesis

ALA synthase Heme (-)