Human tyrosinase related protein-1 (TRP-1) does not function as a DHICA oxidase activity in contrast to murine TRP-1.
Tyrosinase related protein-1 is a melanocyte specific protein and a member of the tyrosinase gene family which also includes tyrosinase and TRP 2 (DOPAchrome tautomerase). In murine melanocytes, TRP-1 functions as a 5,6-dihydroxyindole-2-carboxylic acid [DHICA] oxidase during the biosynthetic conversion of tyrosine to eumelanin and mutations affecting TRP-1 result in the synthesis of brown rather than black pelage coloration. In this study, we examined the putative DHICA oxidase activity of TRP-1 in human melanocytes using several approaches. We first utilized a line of cultured melanocytes established from a patient with a form of oculocutaneous albinism completely lacking expression of TRP-1 (OCA3). This line of melanocytes endogenously exhibited the same amount of DHICA oxidase activity as control melanocytes expressing TRP-1. In other experiments, cultured human fibroblasts were transfected with a cDNA for TRP-1, in either the sense or antisense direction, or with the retroviral vector alone. TRP-1 expression was induced in fibroblasts transfected with the TRP-1 cDNA in the sense direction only. Although TRP-1 was expressed by sense-transfected cells, there was no significant DHICA oxidase activity above controls. These results demonstrate that human TRP-1 does not use DHICA as a substrate for oxidation.
Boissy
R E
RE
Department of Dermatology, University of Cincinnati College of Medicine, OH, USA. boissyre@email.uc.edu
Sakai
C
C
Zhao
H
H
Kobayashi
T
T
Hearing
V J
VJ
D000818:Animals; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D008544:Melanocytes / Q000378:metabolism*; D008562:Membrane Glycoproteins; D051379:Mice; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D013045:Species Specificity; D014162:Transfection
D008562:Membrane Glycoproteins; D011506:Proteins; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C064056:tyrosinase-related protein-1