What enzyme can break down casein in milk, leading to proteolysis?

The correct answer is caseinase because this enzyme specifically targets casein, which is the principal protein found in milk. Caseinase catalyzes the hydrolysis of casein into smaller peptides and amino acids, a process known as proteolysis. This activity is crucial in various biological processes, including digestion and the fermentation of dairy products, such as cheese.

While protease is also an accurate term since it refers to a broader class of enzymes that break down proteins into smaller peptides or amino acids, caseinase is more specific to the casein protein found in milk. This makes caseinase the best choice for the question focused specifically on the breakdown of casein in milk.

Lactase, on the other hand, is an enzyme that breaks down lactose, the sugar present in milk, into glucose and galactose. Amylase is an enzyme that breaks down starches into sugars. Neither lactase nor amylase has any action on casein, thereby reinforcing why caseinase is the most appropriate and correct answer.