Phosphorylation of enzymes
A) has no effect on their catalytic activity.
B) does not require ATP.
C) usually takes place on serine, threonine, and tyrosine residues.
D) is not easily characterized.

Question

Quizplus · Accepted Answer

Phosphorylation of enzymes usually takes place on serine, threonine, and tyrosine residues. This can activate or inactivate the enzyme and regulate its activity.

Answer: D
 Phosphorylation can be quite complex and may involve different types of phosphorylation, different enzymes, and different regulatory mechanisms. It is not always easy to characterize the effects of phosphorylation on enzyme activity.

Therefore, the best choices are C and D. A and B are incorrect because phosphorylation does have an effect on enzyme activity, and it does require ATP.

Phosphorylation of Enzymes