Question

A) List, in order, the three enzymes that catalyze the highly regulated steps in glycolysis. (Don't just enter 1, 2, 3 for reaction numbers - give the reaction number based on the 10 steps of glycolysis.) Reaction # Enzyme Reaction # Enzyme Reaction # Enzyme B) For each of these reactions, name ONE allosteric regulator of the enzyme and whether that regulator inhibits or activates the enzyme. Reaction # allosteric regulator Inhibitor or activator? Reaction # allosteric regulator Inhibitor or activator? Reaction # allosteric regulator Inhibitor or activator?

Answer 1

Answers
A) Reaction >1 - enzyme > hexokinase
Reaction > 3 - enzyme > phosphofructokinase
Reaction >10 - enzyme > pyruvate kinase

B)
Reaction >3 - Phosphosphofructokinase is allosterically inhibited by high levels of ATP.

Reaction >1 - hexokinase is inhibited by glucose-6-phosphate.

Reaction >10 - pyruvate kinase is the enzyme catalyzing the third irreversible and last reversible step in glycolysis. In mammals different genes encode several isozymic forms of pyruvate kinase - the L type and the M type. ATP allosterically inhibits both L and M forms to slow down the process of glycolysis.