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Macrophage migration inhibitory factor (MIF) is a cytokine with broad regulatory functions in innate immunity. MIF belongs to the few cytokines displaying catalytic activities, i.e. MIF has a Pro2-dependent tautomerase and a Cys-Ala-Leu-Cys (CALC) cysteine-based thiol-protein oxidoreductase activity. Previous studies have addressed the roles of the(More)
BACKGROUND Recent studies of melanin biosynthesis have uncovered an unusual enzymatic activity which converts the non-naturally occurring D-isomer of 2-carboxy-2,3-dihydroindole-5,6-quinone (dopachrome) into 5,6-dihydroxyindole-2-carboxylic acid (DHICA). The aim of the present investigation was to isolate and characterize the enzyme catalyzing this(More)
The size of the melanocyte system in humans was estimated as though all active melanocytes in the body were assembled in a single compact organ. Our estimates indicate that the epidermal melanocytes constitute the dominant part of the "melanocyte organ." In an adult human not recently exposed to sunlight, the functionally active epidermal melanocytes form a(More)
Dopa and 5-S-cysteinyldopa levels in serum of albino, red, and black guinea-pigs were quantified. The levels of both amino acids were lower in the albino than in the pigmented animals. It is suggested that the serum levels of dopa and 5-S-cysteinyldopa in pigmented animals reflect tyrosine and dopa oxidation activity in the melanocytes.
A macrophage migration inhibitory factor (MIF), originally described as a product of activated lymphocytes, has been defined as a 12 kDa protein, expressed in a wide variety of tissues. Here MIF is identified as a phenylpyruvate tautomerase (EC having p-hydroxyphenylpyruvate and phenylpyruvate as its natural substrates. The definition of MIF as an(More)
The pigment of the human substantia nigra was isolated after extraction of lipids and proteins with 2% sodium cholate in 30% ethanol followed by 2% sodium dodecyl sulfate in 10% glycerol. The pigment was hydrolysed with HI or degraded by treatment with KMNO4 and the samples were examined for compounds known to derive from pheomelanin(More)
A specific fluorescence is developed in melanocytes, nevus cells, and cells of malignant melanoma by treatment of the tissue with dry formaldehyde gas. The fluorescence is often stronger in melanocytes adjacent to nevi or melanomas than in normal melanocytes. The strongest fluorescence occurs in cells of malignant melanoma. Among the limited number of(More)
Many genes mapping to pigmentation loci are involved in the regulation of melanin synthesis in the mouse. The brown (b) locus controls black/brown coat coloration, and its product has significant homology to the key melanogenic enzyme tyrosinase. This has led to suggestions that the b-protein is itself a melanogenic enzyme. In order to investigate its(More)
The effects of systems generating active oxygen species (superoxide anion, hydrogen peroxide, hydroxyl radical) on tyrosinase have been studied in cultured human melanoma cells. Tyrosinase activity was determined by measuring the quantity of 5-S-L-cysteinyl-L-dopa (5-S-CD) formed in the presence of D,L-dopa and L-cysteine. In some experiments, the enzyme(More)
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(More)