Answer:
Keratin.
Step-by-step explanation:
Keratin protein is present in hair, hooves, nails and skin. keratin is a class of the fibrous structural protein that protects the skin from damage.
Keratin protein reduces the water loss at the skin surface. The keratin is insoluble in water and cannot be dissolved in organic solvents also. Keratin also protect the skin from the stress.
Thus, the answer is keratin.