Evidence and utility of melanin degrading enzymes.

The biochemical synthesis of human melanin is understood in some detail. However, little is known about melanin degradation and catabolism of melanin. We hypothesize that human skin contains enzymes that degrade melanin and these enzymes can be used to reduce skin color. To test this hypothesis, HaCaT keratinocytes and normal human keratinocytes in culture were pulse labeled for one hour with radiolabeled synthetic melanin. This melanin was synthesized in vitro using tyrosinase enzyme from mushrooms and using radiolabeled [14C]3,4-dihydroxyphenylalanine (DOPA) as a substrate. After the initial pulse labeling, samples of both the cells and media were taken at 2, 4, 6 and 18 hours. Over these time periods the counts remaining in the media and cell fraction were significantly decreased. This data suggests the need for new protein synthesis and the lysosome organelle function for the degradation. Melanin degrading extracts isolated from Aspergillus fumigatus and Saccharomyces cerevisiae were applied to human skin. These extracts cause significant reduction in UVB induced pigmentation. These extracts may be useful in developing new whitening products to even skin color and tone.