THE RELATIONSHIP BETWEEN TYROSINASE ACTIVITY AND SKIN COLOR IN HUMAN FORESKINS
THE RELATIONSHIP BETWEEN TYROSINASE ACTIVITY AND SKIN COLOR IN HUMAN FORESKINS
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DOI：
10.1111/1523-1747.ep12872677
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发表时间：
1990-07-01
影响因子：
6.5
通讯作者：
FULLER, BB
中科院分区：
文献类型：
--
作者：
IWATA, M;CORN, T;FULLER, BB
通过测量酪氨酸到多巴的羟化(酪氨酸羟基酶活性)和[14C]酪氨酸到[14C]黑色素的转化(黑色素合成试验)，对黑人和白人包皮样品的酪氨酸酶活性进行了测定。在细胞的颗粒组分(75%)和可溶性组分(25%)中均有酶活性。膜结合的酪氨酸酶很容易被两性或非离子洗涤剂溶解。阴离子洗涤剂胆酸钠抑制了酶的活性。黑色包皮匀浆的酪氨酸酶活性平均为白色皮肤样本的近3倍(黑人为33.8pmmol3H2O/h/mg皮肤，白色皮肤为12.71pmol3H2O/h/mg皮肤)，尽管两组之间存在相当大的重叠。酪氨酸羟基酶和[14C]黑色素测定法测定的酪氨酸酶活性相似，表明酪氨酸羟基酶活性与黑色素合成密切相关。用这两种方法测定的酪氨酸酶活性通常与皮肤黑色素含量相关。从黑白包皮中提取的酪氨酸酶的动力学分析表明，酪氨酸的Km为2.5倍。两种皮肤类型的身高均为10-4M。免疫滴定实验表明，白皮肤和黑皮肤之间酪氨酸酶活性的差异可能不仅是由于黑素细胞中存在不同数量的酶，而且可能是由于黑皮肤和白皮肤中发现的酶的催化活性的差异。
Tyrosinase activity was assayed in black and white human foreskin samples by measuring both the hydroxylation of tyrosine to dopa (tyrosine hydroxylase activity) and the conversion of [14C]tyrosine to [14C]melanin (melanin synthesis assay). Enzyme activity was found both in the particulate (75%) and soluble (25%) fractions of the cell. Membrane-bound tyrosinase was readily solubilized by either zwitterionic or nonionic detergents. The anionic detergent, sodium cholate, inhibited enzyme activity. Tyrosinase activity in black foreskin homogenates averaged almost three times that in white skin samples (33.8 pmols 3H2O/h/mg skin in black and 12.71 pmoles 3H2O/h/mg skin in white skin), although considerable overlap in activities existed among the two groups. Tyrosinase activities measured with two separate assays, tyrosine hydroxylase and [14C]melanin assays, were similar, suggesting that tyrosine hydroxylase activity is tightly coupled to melanin synthesis. Tyrosinase activity determined by either assay method generally correlated with skin melanin content. Kinetic analysis of tyrosinase from black and white foreskin revealed a Km for tyrosine of 2.5 .times. 10-4 M in both skin types. Immunotitration experiments suggested that the difference in tyrosinase activities between white and black skin may be due, not only to different amounts of enzyme present in the melanocytes, but also possibly to differences in the catalytic activities of the enzyme found in melanocytes of black and white skin.