19. Enzymes

Match the terms (a) allosteric control, (b) feedback control, and (c) zymogen activation with each of the following:

_______ Pepsinogen is converted into its active form (pepsin) by losing 44 amino acids from its primary structure.

_______ A small molecule attaches to the enzyme and makes an active site available to a substrate.

_______ The end-product of a metabolic pathway decreases the activity of the enzyme in the first step.

_______ Alanine binds to pyruvate kinase and reduces active site availability for the enzyme's substrate.

Match the terms (a) allosteric control, (b) feedback control, (c) zymogen activation, and (d) phosphorylation/dephosphorylation with each of the following:

_______ Proline inhibits glutamate 5-kinase, the enzyme in the first step of the biosynthesis of proline from glutamate. 

_______ Glycogen synthase loses its catalytic activity when it is phosphorylated.

_______ Proelastase is converted to its active form elastase when it loses some part of its polypeptide backbone.

_______ Adenosine monophosphate binds to phosphofructokinase-1 and increases its activity.

Activation of a zymogen is by covalent modification. How might phosphorylation or dephosphorylation (also covalent modification) modify an enzyme to make it more active (or more inactive)?

Which type of enzyme regulation is best for the following situations?

a. An enzyme that becomes overactive during a disease

b. An enzyme needed only when there is low blood glucose

c. An enzyme that springs into action when a traumatic injury occurs

d. An enzyme needed only during adolescence

Explain how the following mechanisms regulate enzyme activity.

b. Genetic control