| First Author | Winder AJ | Year | 1994 |
| Journal | Pigment Cell Res | Volume | 7 |
| Issue | 5 | Pages | 305-10 |
| PubMed ID | 7886003 | Mgi Jnum | J:22250 |
| Mgi Id | MGI:70131 | Doi | 10.1111/j.1600-0749.1994.tb00632.x |
| Citation | Winder AJ, et al. (1994) The mouse brown (b) locus protein functions as a dopachrome tautomerase. Pigment Cell Res 7(5):305-10 |
| abstractText | The mouse b locus controls black/brown coat coloration. Its product, the b-protein or TRP-1, has significant homology to tyrosinase, and this has led to suggestions that the b-protein is itself a melanogenic enzyme. In order to investigate its function, we have used lines of mouse fibroblasts stably expressing the b-protein. We were unable to confirm previous reports that the b-protein has tyrosinase or catalase activity, but detected stereospecific dopachrome tautomerase activity in b-protein-expressing fibroblasts. This dopachrome tautomerase binds to Concanavalin A-Sepharose, and the major product of its action on L-dopachrome is 5,6-dihydroxyindole-2-carboxylic acid, as expected for the mammalian enzyme. Since this activity is not present in untransfected fibroblasts we conclude that the b-protein has dopachrome tautomerase activity. Further supporting evidence comes from the analysis of melanin metabolites produced by fibroblasts expressing tyrosinase alone, or in combination with the b-protein. Culture medium from the line expressing both proteins contains significant amounts of methylated carboxylated indoles, such as 6-hydroxy-5-methoxyindole-2-carboxylic acid, which would be expected in cells with an active dopachrome tautomerase. The levels of these compounds in medium from cells expressing tyrosinase alone are approximately 20-fold lower, and not significantly above background. Hence, it appears that the b-protein acts as a dopachrome tautomerase in vivo as well as in vitro. |
