Question

Lactoperoxidase belongs to which one of the following groups of enzymes?

• A. Lyase
• B. Hydrolase
• C. Oxidoreductase
• D. Transferase

Hint:

Enzyme Classifications in Milk:
Oxidoreductases (EC 1) = LACTOPEROXIDASE, Catalase, Xanthine Oxidase.
Hydrolases (EC 3) = Alkaline Phosphatase, Lipase, Lysozyme.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Enzyme Commission (EC) systematic classification: Lactoperoxidase (EC 1.11.1.7) is a heme-containing oxidoreductase that catalyzes electron transfer from thiocyanate to hydrogen peroxide.
Key Formula or Approach:
\[ \text{EC 1.11.1.7: } \text{H}_2\text{O}_2 + \text{SCN}^- \xrightarrow{\mathbf{Lactoperoxidase \text{ (EC 1: Oxidoreductase)}}} \text{OSCN}^- + \text{H}_2\text{O} \]

Step 2: Detailed Explanation:
According to the International Union of Biochemistry and Molecular Biology (IUBMB Enzyme Commission Classification):
- Lactoperoxidase (LP) (EC 1.11.1.7) is the second most abundant natural protective enzyme in bovine milk ($30\text{ mg/L}$):
1. It belongs to Class 1: Oxidoreductases (C), specifically the peroxidase subclass (EC 1.11).
2. It possesses a protoporphyrin IX heme prosthetic group that catalyzes the oxidation-reduction electron transfer from donor substrates (such as thiocyanate, $\text{SCN}^-$, or iodide, $\text{I}^-$) using hydrogen peroxide ($\text{H}_2\text{O}_2$) as the terminal electron acceptor to generate antimicrobial hypothiocyanite ($\text{OSCN}^-$).
3. (Hydrolases = Class 3 like Lipase/Alkaline phosphatase; Lyases = Class 4; Transferases = Class 2).

Step 3: Final Answer:
Hence, Lactoperoxidase belongs to Oxidoreductase, matching option (C).