ABC26IN0037 · Bioinorganic Chemistry
Subject: Inorganic Chemistry · Chapter: Bioinorganic Chemistry · Topic: Iron Sulfur Proteins · Exam: CSIR-NET 2013 · Marks: 2 · Difficulty: Medium
Oxidised form of enzyme catalase (structure A); prepared by the reaction of $[\mathrm{Fe(P)}]^{+}$ ( $\mathrm{P}=$ porphyrin) with $\mathrm{H_2O_2}$ has green color because 
A(substitutents on ring are removed for clarity)
A(substitutents on ring are removed for clarity)(a)Oxidation state of iron changed from $\mathrm{Fe}^{\text {III }}$ to $\mathrm{Fe}^{\text {IV }}$
(b)Porphyrin ring is oxidized by one electron
(c)$\pi-\pi^{*}$ transition appears in the visible region
(d)$\mathrm{Fe^{IV}}$ is coordinated with anionic tyrosinate ligand in axial position.
Answer
Answer (as printed): A
Explanation
Catalase is a tetramer of four polypeptide chains covering 500 amino acids. It works as
\[ \mathrm{H_2O_2 + Fe^{III}\text{-}E \rightarrow H_2O + O=Fe^{IV}\text{-}E} \]
\[ \mathrm{H_2O_2 + O=Fe^{IV}\text{-}E^{+} \rightarrow H_2O + Fe^{III}\text{-}E + O_2} \]
The colour arises as $\mathrm{Fe^{III}}$ changes into $\mathrm{Fe^{IV}}$.