Rate limiting enzymes

Pathway

Rate-Limiting Enzyme

Function

Glycolysis

Phosphofructokinase-1
(PFK-1)

Catalyzes the conversion of fructose-6-
phosphate to fructose-1,6-bisphosphate

Gluconeogenesis

Fructose-1,6-
bisphosphatase

Catalyzes the conversion of fructose-1,6-
bisphosphate to fructose-6-phosphate

Citric Acid Cycle
(TCA Cycle)

Isocitrate
dehydrogenase

Catalyzes the oxidative decarboxylation
of isocitrate to α-ketoglutarate

Glycogenolysis

Glycogen
phosphorylase

Catalyzes the breakdown of glycogen
to glucose-1-phosphate

Glycogenesis

Glycogen synthase

Catalyzes the formation of glycogen
from glucose-1-phosphate

Pentose phosphate
pathway
(HMP shunt)

Glucose-6-phosphate
dehydrogenase

Catalyzes the oxidation of glucose-6-
phosphate to 6-phosphoglucono-δ-lactone

Urea cycle

Carbamoyl phosphate
synthetase I

Catalyzes the formation of carbamoyl
phosphate from ammonia and bicarbonate

Fatty acid
synthesis

Acetyl-CoA
carboxylase

Catalyzes the carboxylation of acetyl-CoA
to malonyl-CoA

β-oxidation (Fatty
acid oxidation)

Carnitine acyl
transferase I

Catalyzes the transfer of fatty acyl groups
to carnitine for transport into mitochondria

Cholesterol
synthesis

HMG-CoA reductase

Catalyzes the conversion of HMG-CoA
to mevalonate

Ketogenesis

HMG-CoA synthase

Catalyzes the formation of HMG-CoA
from acetoacetyl-CoA

Bile acid
synthesis

7-alpha-hydroxylase

Catalyzes the conversion of cholesterol
into 7α-hydroxycholesterol

Purine synthesis
(de novo)

Glutamine-PRPP
amidotransferase

Catalyzes the conversion of PRPP to
5-phosphoribosylamine

Pyrimidine synthesis
(de novo)

Carbamoyl phosphate
synthetase II

Catalyzes the formation of carbamoyl
phosphate from glutamine and CO2