Lecture 13 - Enzymes III

Question 1

ATCase acts as a(n) ______ of pyrimidine synthesis depending on CTP vs ATP binding.

Answer 1

Regulator

Question 2

ATCase regulatory and catalytic subunits are bound to each other by ____

Answer 2

a zinc domain

Question 3

CTP works to “lock” ATCase into the ____-state (doesn’t bind substrate)

Answer 3

tense or “T-state”

Question 4

When in the T-state, ATCase does or does not produce pyrimidines

Answer 4

does not

Question 5

This class of enzyme adds inorganic phosphates to proteins

Answer 5

Kinases

Question 6

This class of enzyme removes inorganic phosphates from proteins

Answer 6

phosphatase

Question 7

Why is AMP a potent regulator of enzymes (specifically kinases)?

Answer 7

AMP is produced when Pi is removed from ATP (as a result of cellular E* stores being low). AMP activates kinases to produce more ATP by phosphorylation

Question 8

What is the name of an inactive protein that is awaiting cleavage to become active?

Answer 8

a “zymogen”

Question 9

Pepsinogen is one of the few protease zymogens found in the _____

Answer 9

stomach

Question 10

Two types of allosteric control in enzymes

Answer 10

Inhibition and activation

Question 11

All substrates must bind to the enzyme prior to product release in this type of bisubstrate reactions

Answer 11

What is “sequential reactions?”

Question 12

One substrate binds, product is released, then another substrate binds to enzyme in this type of bisubstrate reaction.

Answer 12

Double-displacement reaction

Question 13

What is the (+) allosteric regulator for ATCase? Why is this particular molecule an ATCase inhibitor?

Answer 13

ATP; ATP is the byproduct of purine synthesis-therefore, increased ATP signifies that the “competing” purine pathway is more active. Since purines bind pyrimidines, it makes sense to increase pyrimidine synthesis!!!

Question 14

Acts to dephosphorylate adenyl cyclase when intracellular calcium is high

Answer 14

PP2B (aka “calcineurin”)