Rate-Limiting Steps, USMLE Flashcards
Rate limiting step for glycogenolysis
Glycogen phosphorylase
Rate limiting step for HMP shunt
G6PD
Rate limiting step for De novo pyrimidine synthesis
Carbamoyl phosphate synthetase II
Rate limiting step for De novo purine synthesis
Glutamine-PRPP aminotransferase
Rate limiting step for glycolysis
Phosphofructokinase-1
Rate limiting step for Gluconeogenesis
fructose-1,6-bisphosphatase
Rate limiting step for TCA cycle (krebb cycle)
Isocitrate dehydrogenase
Rate limiting step for glycogen synthesis
glycogen synthase
Rate limiting step for Urea cycle/synthesis
carbamoyl phosphate synthetase I (mitochondria)
Rate limiting step for Fatty acid synthesis
Acetyl-coA carboxylase (ACC)
Rate limiting step for fatty acid oxidation
Carnitine acyltransferase I
Rate limiting step for ketogenesis
HMG-coA synthase
Rate limiting step for cholesterol synthesis
HMG-CoA reductase
Rate limiting step for heme synthesis
Aminolevulinate synthase (ALA synthetase)
Rate limiting step for bile acid synthesis
7-alpha-hydroxylase
Gluconeogenesis enzyme that is stimulated by cortisol, epinephrine, and glucagon when energy levels from beta oxidation are adequate
Phosphoenolpyruvate carboxykinase
Ezyme bridges glycolysis with the tricarboxylic acid cycle and requires co-factors from the electron transport chain (NAD/FAD; If hypoxic = no cofactors –> no ezyme activity)
Pyruvate dehydrogenase ( Pyruvate + co A —(enzyme used) –> acetyl-co a)
Rate-limiting enzyme: Uric acid metabolism
Xanthine oxidase
Catecholamine synthesis
Tyrosine hydroxylase
