Rate-limiting enzymes and control points — Flashcards

Flashcard 1: Hexokinase is characterized by a _____ Vmax relative to glucokinase

Answer: low

Flashcard 2: Hexokinase is regulated via negative feedback by _____

Answer: glucose-6-phosphate

Flashcard 3: Fructose bisphosphatase-2 and phosphofructokinase-2 are the same bifunctional enzyme whose function is reversed by phosphorylation by _____

Answer: protein kinase A

Flashcard 4: Glucokinase is regulated via negative feedback by _____

Answer: fructose-6-phosphate

Flashcard 5: Is hexokinase activity inhibited by glucose-6-phosphate? _____

Answer: Yes

Flashcard 6: Which glycolysis enzyme deficiency is the second most common cause of hemolytic anemia? _____

Answer: Pyruvate kinase deficiency

Flashcard 7: What is the function of the bifunctional enzyme Phosphofructokinase-2/Fructose bisphosphatase-2 (PFK-2/FBP-2)?

Answer: A bifunctional enzyme that regulates the levels of Fructose-2,6-bisphosphate (F-2,6-BP), thereby balancing glycolysis and gluconeogenesis.

Extra: In the well-fed state, PFK-2 is active (increased F-2,6-BP) → stimulates Glycolysis.\nIn the fasting state, FBP-2 is active (decreased F-2,6-BP) → stimulates Gluconeogenesis.

Flashcard 8: Where does glycolysis take place?

Answer: cytoplasm

Flashcard 9: What is the rate-limiting enzyme of glycolysis?

Answer: Phosphofructokinase-1 (PFK-1)

Extra: The three irreversible steps of glycolysis are catalyzed by:\n1. Hexokinase/Glucokinase\n2. Phosphofructokinase-1 (Rate-limiting step)\n3. Pyruvate kinase\n\nPFK-1 is inhibited by ATP and Citrate, and activated by AMP and Fructose-2,6-bisphosphate.

Flashcard 10: What enzyme converts pyruvate to lactate?

Answer: lactate dehydrogenase (LDH)