title: Oxidation of dopa in the skin of black and albino mice.
abstract: The dopa oxidase activity of tyrosinase in the skin from albino and black mice was assayed using a technique based on the formation of two diastereomers of 5-S-cysteinyldopa when incubating tissue extracts with both L-dopa and D-dopa as substrates in the presence of cysteine. The amounts of 5-S-L-cysteinyl-L-dopa and 5-S-L-cysteinyl-D-dopa formed were then determined. In the extract from black mouse skin the L-L-diastereomer was produced in more than ten times the amount of the L-D-diastereomer. This stereospecific dopa-oxidation is indicative of the presence of tyrosinase and corresponds well with earlier determinations of the rates of oxidation for human tyrosinase, using L-dopa and D-dopa as substrates. Stereospecific dopa oxidation was absent in albino skin, and the nonspecific dopa-oxidation was two orders of magnitude less than the dopa oxidation in black skin. The study demonstrates the lack of tyrosinase activity in albino skin, and quantifies the non-specific dopa oxidation. The lack of tyrosinase activity in the eluates from albinotic skin was found not to be due to the presence of a tyrosinase inhibitor.
mesh_terms: D000417:Albinism / Q000378:metabolism; D000818:Animals; D003548:Cysteinyldopa / Q000096:biosynthesis; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008543:Melanins / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010084:Oxidation-Reduction; D012867:Skin / Q000378:metabolism*; D012880:Skin Pigmentation; D013237:Stereoisomerism
chemical_list: D008543:Melanins; D003548:Cysteinyldopa; D004295:Dihydroxyphenylalanine; D014442:Monophenol Monooxygenase