Question

Which of the following enzyme activity is associated with the Ceruloplasmin?

• A. Reductase
• B. Hydrolase
• C. Oxidase
• D. Transferase

Hint:

Think: "Ceruloplasmin = Ferroxidase."
Since a ferroxidase oxidizes iron ($Fe^{2+} \rightarrow Fe^{3+}$) using oxygen, its enzyme class is an oxidase.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ceruloplasmin is a major copper-carrying metalloprotein found in blood plasma, synthesized primarily in the liver.
It carries more than $95\%$ of the total copper in healthy human plasma.

Step 2: Detailed Explanation:
Beyond acting as a copper transport protein, ceruloplasmin possesses enzymatic activity.
Specifically, it acts as a ferroxidase, which is a subclass of the oxidase enzyme family.
Iron is absorbed in the gastrointestinal tract and stored in tissues in its reduced ferrous state ($Fe^{2+}$).
However, to be loaded onto the transport protein transferrin, iron must be oxidized to its ferric state ($Fe^{3+}$).
Ceruloplasmin catalyzes this oxidation reaction:
\[ 4Fe^{2+} + 4H^{+} + O_{2} \rightarrow 4Fe^{3+} + 2H_{2}O \]
This ferroxidase activity prevents the accumulation of free ferrous iron, which can generate toxic free radicals via the Fenton reaction.
Because it couples the reduction of molecular oxygen to water with the oxidation of substrate iron, its primary enzymatic classification is an oxidase.

Step 3: Final Answer:
The enzymatic activity associated with ceruloplasmin is that of an oxidase (specifically ferroxidase).