Based on the behaviour of the metalloenzymes, consider the following statements
\[ \begin{array}{l} \text{(A) In the enzymes, the zinc activates } \mathrm{O_2}\text{, to form peroxide species.} \\ \text{(B) In the enzymes, the zinc activates } \mathrm{H_2O} \text{ and provides a zinc boud hydroxide.} \\ \text{(C) In the oxidases, the iron activates } \mathrm{O_2}\text{, to break the bonding between the two oxygens} \\ \text{(D) Zinc ion acts as a nucleophile and attacks at the peptide carbonyl} \end{array} \]
The set of correct statements is,
(a)A and B
(b)B and C
(c)C and D
(d)A and D
Answer
Answer: B ✓ checked by 4AB · confidence high
Explanation
Zn²⁺ is redox-inactive; it lowers the pKa of bound water, giving the nucleophilic Zn–OH. Iron oxidases activate O₂ and cleave the O–O bond. Zn²⁺ is a Lewis acid, not a nucleophile. B and C (b).