Question

How are serine proteases regulated to cleave some peptide bonds more frequently than others?

	A. Substrate conformation changes to hide certain cleavage sites on binding to enzyme
	B. Small molecules block some sites
	C. The enzyme dimerizes around the substrate
	D. There is a b-pleated sheet interaction between enzyme and substrate
	E. Zymogen can be activated only at certain sites

Answer 1

Proteases are enzymes which digest proteins in our body. Serine protease is one such enzyme, which employs serine as nucleophilic amino acid. However, it should not be active a the time, else it would digest essential structural proteins of body. To regulate this, the active site of serine protease is blocked by certain small molecules which mimic as substrate.

Thus, the correct choice should be:

(b) Small molecules block some sites.