Question

Match List-I with List-II


List-I (Enzyme) & List-II (Post Translation modification for regulation)
(A). Nitrogenase & (I). Phosphorylation and 14:3:3 proteins
(B). Glutamine synthetase & (II). ADP-ribosylation
(C). Nitrate reductase & (III). Adenylylation
(D). Rubisco & (IV). S-Nitrosylation


Choose the correct answer from the options given below:

• (A) - (I), (B) - (II), (C) - (III), (D) - (IV)
• (A) - (II), (B) - (I), (C) - (III), (D) - (IV)
• (A) - (II), (B) - (III), (C) - (I), (D) - (IV)
• (A) - (III), (B) - (II), (C) - (I), (D) - (IV)

Hint:

Associate the binding of 14-3-3 proteins with the phosphorylated form of Nitrate Reductase, which is a classic regulatory pathway in plant nitrogen metabolism.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Post-translational modifications (PTMs) allow cells to rapidly regulate enzyme activity in response to changing metabolic and environmental conditions.

Step 2: Detailed Explanation:
Let us match each metabolic enzyme with its post-translational regulation mechanism:
- (A) Nitrogenase: In many nitrogen-fixing bacteria, nitrogenase activity is shut off in response to ammonium availability through reversible ADP-ribosylation (II) of the dinitrogenase reductase protein.
- (B) Glutamine synthetase: In prokaryotes, this key nitrogen-assimilation enzyme is regulated by adenylylation (III), where attachment of an AMP moiety inactivates the enzyme.
- (C) Nitrate reductase: In plant cells, nitrate reductase is inactivated when a specific serine residue is phosphorylated, allowing a 14-3-3 inhibitor protein to bind and block activity (I).
- (D) Rubisco: Rubisco activity is regulated by nitric oxide levels through S-Nitrosylation (IV) of specific cysteine residues.
This yields the correct matching sequence: (A)-(II), (B)-(III), (C)-(I), (D)-(IV).

Step 3: Final Answer:
Hence, the correct option is (C).