Aminoacids--precursors of melanin synthesis in hamster melanoma.

The role of L-tyrosine, L-phenylalanine, L-dihydroxyphenylalanine (dopa) and L-tryptophan in melanin biosynthesis in melanotic hamster melanoma IC-Sofia was investigated with the aid of 14C-aminoacids. Tyrosine and phenylalanine were found to be the main melanin precursors: about 64.5% of total melanin labeling was due to tyrosine incorporation and 27.4% to phenylalanine incorporation. Negligible proportions of melanin radioactivity (5.7% and 2.4%, respectively) resulted from dopa and tryptophan utilization in melanin synthesis. The involvement of each of the aminoacids under investigation in melanin synthesis in vivo is discussed.