... rate-limiting enzyme in melanin synthe-sis, tyrosinase, is increased and skin pigmentation ispromoted. Melanin pigments are complex heteropolymers,which can be classified into two main groups: ... eumelanins, and the reddish to yellow, sulfur-containing phaeomelanins [17]. Although both types ofmelanins are found in different relative proportions in allskin types, the phaeomelanin/eumelanin ... residue in TM2, namelyGlu92Lys, and that Glu92 in Mc1r is equivalent to Glu94 in human MC1R. Interestingly, the constitutively active som-ber Mc1r might also display a reduced binding affinity [38].Therefore,...