Odh G, Hindemith A, Rosengren A M, Rosengren E, Rorsman H
Department of Pharmacology, University of Lund, Sweden.
Biochem Biophys Res Commun. 1993 Dec 15;197(2):619-24. doi: 10.1006/bbrc.1993.2524.
Two membrane bound enzymes which tautomerize L-dopachrome and are specific for the L-isomer of dopachrome have been defined in melanin forming cells. Another enzyme that tautomerizes D-dopachrome with concomitant decarboxylation to give 5,6-dihydroxyindole (DHI) was found in the cytoplasm of human melanoma cells, human liver and in all of the organs studied in rat. The decolorization of D-dopachrome with the formation of DHI was used in monitoring the isolation of a tautomerase from liver of male rats and therefore the enzyme is provisionally called D-dopachrome tautomerase. The molecular weight of D-dopachrome tautomerase monomer was approximately 12 kD and its N-terminal amino acid sequence was P-F-V-E-L-E-T-N-L-P-A-. The Km for D-dopachrome was 1.5 mM and Vmax 0.5 mmol per min and mg protein.
在形成黑色素的细胞中已确定有两种膜结合酶，它们能使L - 多巴色素互变异构，且对多巴色素的L - 异构体具有特异性。在人黑色素瘤细胞、人肝脏以及在大鼠研究的所有器官的细胞质中发现了另一种酶，该酶能使D - 多巴色素互变异构并伴随脱羧反应生成5,6 - 二羟基吲哚（DHI）。利用D - 多巴色素脱色形成DHI来监测从雄性大鼠肝脏中分离出一种互变异构酶，因此该酶被暂称为D - 多巴色素互变异构酶。D - 多巴色素互变异构酶单体的分子量约为12 kD，其N端氨基酸序列为P - F - V - E - L - E - T - N - L - P - A -。D - 多巴色素的米氏常数（Km）为1.5 mM，最大反应速度（Vmax）为每分钟0.5 mmol每毫克蛋白质。
