College

Diisopropylphosphofluoridate (DIPF) inactivates chymotrypsin by covalently modifying serine 195. Which statement is true of DIPF's inhibitory mechanism?

A. It forms a reversible bond with serine 195.
B. It irreversibly binds to histidine residues.
C. It disrupts the hydrogen bonding in the active site.
D. It covalently modifies serine 195.

Answer :

Final answer:

DIPF inactivates chymotrypsin by irreversibly covalently modifying serine 195, which means it forms a bond that cannot be easily reversed.

Explanation:

The inhibitory mechanism of Diisopropylphosphofluoridate (DIPF) involves the covalent modification of serine 195 in chymotrypsin. The nature of this binding is irreversible, meaning that once DIPF binds to serine, it cannot be easily removed or reversed, effectively inactivating the enzyme. This mode of inhibition is similar to the actions of certain nerve gases, which are known to permanently inactivate enzymes like acetylcholinesterase by forming a covalent bond with a serine residue at the active site. This is distinctly different from reversible inhibition, where the inhibitor binds reversibly and its effects can be nullified.