Rate-Limiting Steps In Metabolism

Front 1

Reactions in Mitochondria

Back 1

**breakdown/energy pathways

MITO FATO:
FA oxidation
Acetyl-CoA production
TCA cycle
Oxidative phosphorylation

BOTH: HUGs take 2
Heme synthesis (1st and last steps- ALA synthase; ferrochetalase)
Urea cycle (CPSI, OTC)
Gluconeogenesis (Pyr carboxylase (pyruvate to oxaloacetate)

Front 2

Reactions in cytoplasm

Back 2

**synthesis reactions
Glycolysis, FA synthesis, HMP shunt, Protein synthesis (RER), steroid synthesis (SER)

Both:
Heme synthesis
Urea cycle
Gluconeogenesis

Front 3

Rate-limiting step:
Glycolysis

Back 3

phosphofructokinase-1

Front 4

Rate-limiting step:
Gluconeogenesis

Back 4

Fructose-1,6,bisphosphatase

Front 5

Rate-limiting step:
TCA

Back 5

Isocitrate dehydrogenase

Front 6

Rate-limiting step:
Glycogen synthesis

Back 6

Glycogen synthase

Front 7

Rate-limiting step:
Glycogenolysis

Back 7

Glycogen phosphorylase

Front 8

Rate-limiting step:
HMP shunt

Back 8

G6PD
Glucose-6-phosphate dehydrogenase

Front 9

Rate-limiting step:
De novo pyrimidine synthesis

Back 9

Carbamoyl phosphate synthestase II (in cytosol)

Front 10

Rate-limiting step:
De novo purine synthesis

Back 10

Glutamine-PRPP amidotransferase

Front 11

Rate-limiting step:
Urea cycle

Back 11

Carbamoyl phosphate synthetase I
(mitochondria)

Front 12

Rate-limiting step:
FA synthesis

Back 12

Acetyl-CoA carboxylase (ACC)

Front 13

Rate-limiting step:
FA oxidation

Back 13

Carnitine acyltransferase I

Front 14

Rate-limiting step:
Ketogenesis

Back 14

HMG-CoA synthase

Front 15

Rate-limiting step:
Cholesterol synthesis

Back 15

HMG-CoA reductase (target for statins)

Front 16

Rate-limiting step:
Heme synthesis

Back 16

Aminolevulinic Acid synthase (ALA synthase)

Front 17

Rate-limiting step:
Bile acid synthesis

Back 17

7-alpha hydroxylase