Inhibitory Action of Thiouracil, Thiocarbamide and Other Compounds on Melanin Formation by Tyrosinase

Summary and Conclusions 1. Melanin formation in a tyrosinase-tyrosine system was inhibited by thiouracil, thiocarbamide, glutathione, cysteine, ascorbic acid, p-aminobenzoic acid, and sodium sulfathiazole and sulfa-diazine. 2. This inhibition is overcome by copper and by iodoacetic acid. 3. Thiouracil and ascorbic acid were more potent inhibitors than the other compounds studied. 4. Avail” able data do not permit a definite statement regarding the nature of the inhibitory mechanism, but they suggest a direct anti-enzyme action.