Rate-limiting Enzymes

Question 1

Glycolysis

Answer 1

Phosphofructokinase-1 (PFK-1)

*Regulation: +AMP, +fructose-2,6-BP, -ATP, -citrate

Question 2

Gluconeogenesis

Answer 2

Fructose-1,6-bisphosphatase

*Regulation: +ATP, -AMP, -fructose-2,6-BP

Question 3

TCA cycle

Answer 3

Isocitrate dehydrogenase

*Regulation: +ADP, -ATP, -NADH

Question 4

Glycogen synthesis

Answer 4

Glycogen synthase

*Regulation: +Glucose, +Insulin, -epinephrine, -glucagon

Question 5

Glycogenolysis

Answer 5

Glycogen phosphorylase (adds phosphate without using ATP)
*Regulation: +AMP, +epinephrin, +glucagon, -insulin, -ATP

Question 6

HMP shunt

Answer 6

Glucose-6-phosphate dehydrogenase

*Regulation: +NADP+, -NADPH

Question 7

De novo pyrimidine synthesis

Answer 7

Carbamoyl phosphate synthetase II

Question 8

De novo purine synthesis

Answer 8

Glutamine-PRPP amidotransferase

*Regulation: -AMP, -IMP, -GMP

Question 9

Urea cycle

Answer 9

Carbamoyl phosphate synthetase I

*Regulation: +N-acetylglutamate

Question 10

Fatty acid synthesis

Answer 10

Acetyl-CoA carboxylase (ACC)
(needs Biotin)
*Regulation: +insulin, +citrate, -glucagon, -palmitoyl-CoA

Question 11

Fatty acid oxidation

Answer 11

Carnitine acyltransferase I

*Regulation: -malonyl-CoA

Question 12

Ketogenesis

Answer 12

HMG-CoA synthase

Question 13

Cholesterol synthesis

Answer 13

HMG-CoA reductase

*Regulation: +insulin, +thyroxine, -glucagon, -cholesterol