thermal liable tyrosinase (heat sensitive tyrosinase)

Cats of the Himalayan series (colour points, minks, sepias (semi-albinos) have heat-sensitive tyrosinase. Normal tyrosinase converts the amino acid tyrosine into melanin (pigment). In Himalayan series cats this enzyme diminishes at normal body temperature, thus colour is formed only on the colder extremities of the body (legs, tail ears, face). A sepia cat (cb/cb) has only slightly thermo-liable tyrosinase, a mink cat (cb/cs) has slightly more thermo-liable tyrosinase, and a colour point cat (cs/cs) has even more thermo-liable tyrosinase. Then there are the albino cats, which may be lacking tyrosinase all together, as in the pink eyed albino cat (ca/ca). See Tyrosine.

SOURCE: cat-world.com.au