HUMAN TRP-1 HAS TYROSINE-HYDROXYLASE BUT NO DOPA OXIDASE ACTIVITY

被引:43
作者
ZHAO, HQ [1 ]
ZHAO, Y [1 ]
NORDLUND, JJ [1 ]
BOISSY, RE [1 ]
机构
[1] UNIV CINCINNATI,COLL MED,DEPT DERMATOL,231 BETHESDA AVE,MAIL LOCATION 0592,CINCINNATI,OH 45267
来源
PIGMENT CELL RESEARCH | 1994年 / 7卷 / 03期
关键词
MELANOGENESIS; TYROSINASE; TRP-1; ENZYMATIC FUNCTION; MELANOCYTE;
D O I
10.1111/j.1600-0749.1994.tb00040.x
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Human TRP-1 has been immunopurified from normal human melanocytes cultured from black neonatal subjects and used to investigate the catalytic function of TRP-1 for the two substrates, L-tyrosine and L-DOPA. Immunopurified TRP-1 did not demonstrate DOPA staining on SDS/PAGE nor DOPA oxidase (DO) activity with either routine or modified assays. The purified TRP-1 also demonstrated no tyrosine hydroxylase (TH) activity using the routine Pomerantz assay. However, there was apparent TH activity exhibited by immunopurified TRP-1 under conditions with low tyrosine concentration (less-than-or-equal-to 0.8 muCi/ml of H-3-tyrosine), prolonged incubation time (i.e., overnight) and in the absence of the cofactor L-DOPA. Using these latter specific conditions, TH activity was also detected in cell lysates from a tyrosinase-negative albino melanocyte line which exhibited no TH activity with the routine Pomerantz assay. In addition, TH activity under low substrate assay conditions was not exhibited in a melanocyte line derived from a TRP-1 deficient, Brown albino individual. However, the absence of TH in this Brown albino cell line could be compensated for by the addition of L-DOPA to the assay. These results suggested that TRP-1 has some tyrosine hydroxylase but no DOPA oxidase activity. We propose that one function of TRP-1 is to modulate tyrosinase activity by making DOPA available as a cofactor to perpetuate the initial steps in melanogenesis.
引用
收藏
页码:131 / 140
页数:10
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