Gray hair results from a decline in which enzyme?

The correct choice is linked to the role of the enzyme tyrosinase, which is crucial for the production of melanin, the pigment responsible for the color of hair, skin, and eyes. As people age, the activity of tyrosinase decreases, leading to a reduction in melanin production in the hair follicles. As melanin levels drop, hair begins to lose its color and turns gray or white.

In contrast, catalase is an enzyme that breaks down hydrogen peroxide, and while it plays a role in cellular processes, it is not directly related to hair pigmentation. Lactase is involved in the digestion of lactose, the sugar found in milk, and is not relevant to hair color. Amylase assists in the breakdown of starches into sugars and also does not have a role in the pigmentation of hair. Therefore, the decline in tyrosinase is the specific factor that results in the graying of hair.