Question

Alpha-lactalbumin is important for regulating _____________ synthesis

• A. Lactose
• B. Whey proteins
• C. Casein
• D. Vitamin B1

Hint:

Without \(\alpha\)-lactalbumin, galactosyltransferase cannot bind glucose efficiently, preventing the synthesis of lactose in the mammary gland.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
\(\alpha\)-Lactalbumin is a major whey protein that plays a dual role: it is a highly nutritious protein and a vital regulatory subunit of an enzyme complex.

Step 2: Detailed Explanation:
- Within the mammary gland, lactose is synthesized by the enzyme complex lactose synthase.
- This enzyme is a dimer composed of two distinct proteins:
1. Galactosyltransferase: The catalytic subunit, which normally transfers galactose to glycoproteins.
2. \(\alpha\)-Lactalbumin: The regulatory subunit.
- Binding of \(\alpha\)-lactalbumin to galactosyltransferase alters its substrate specificity, increasing its affinity for glucose by about 1000-fold.
- This conformational shift enables the enzyme to catalyze the synthesis of lactose from UDP-galactose and glucose.

Step 3: Final Answer
\(\alpha\)-Lactalbumin is essential for regulating lactose synthesis.