Production of melanin precursors by a mutant of Tetrahymena thermophila.

A mutant of Tetrahymena thermophila, "pig," excretes melanin precursors into the culture medium where spontaneous polymerization to melanin occurs. The precursors, probably oxidation products of catecholamines, are produced in large amounts by the mutant by decarboxylation of tyrosine and hydroxylation of the resulting tyramine. Overproduction and excretion of precursors by the mutant appears to result from elevated specific activity of L-aromatic amino acid decarboxylase (DOPA decarboxylase) (E.C. 4.1.1.26).