Disease relevance of C05664

• 5,6-Dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) were quantitated by HPLC with fluorescent detection, after DC incubation with heated and unheated preparations of B-16 melanoma derived dopachrome oxidoreductase (DCOR) [1].

High impact information on C05664

• Tyrosinase has the unusual property of catalyzing three distinct reactions within a single biochemical pathway: the hydroxylation of a monophenol, the dehydrogenation of a catechol, and the dehydrogenation of a dihydroxyindole [2].
• It has been proposed that tyrosinase is also able to oxidize 5,6-dihydroxyindole (DHI), a later product in the melanogenic pathway, to indole-5,6-quinone [3].
• The antioxidant properties of DHI- and DHICA-melanins have been investigated in comparison with other kinds of melanins [4].
• Dopaquinone redox exchange with dihydroxyindole and dihydroxyindole carboxylic acid [5].
• In the murine system, Tyrp1 expresses significant dihydroxyindole carboxylic acid oxidase (i.e. DHICA oxidase) activity [6].

Biological context of C05664

• Samples obtained by irradiation of tyrosine solution revealed the formation of 5,6-dihydroxyindole (DHI) oligomers up to pentamers at 120 min; the reaction kinetics were markedly enhanced in the presence of tyrosinase [7].
• Under action of DCF, L-dopachrome was converted into dihydroxyindole, which showed that a decarboxylation occured in the course of reaction [8].
• We report now evidence that DHI, DHICA and CD exert potent inhibitory effects in different in vitro models of lipid peroxidation [9].

Anatomical context of C05664

• Our data suggest that the absence of in vivo melanin polymer formation within CV can be explained by formation by these organelles of relatively stable DHI2C rather than easily polymerizing DHI [10].
• 2. Dopa and 5,6-dihydroxyindole (DHI) were two hemolymph components identified in hosts exhibiting a melanotic encapsulation response [11].
• Due to the lower reactivity of DHICA in comparison to DHI, DCT could provide a protective mechanism against the cytotoxicity of decarboxylated indolic melanogenic intermediates by limiting the formation of these highly reactive decarboxylated species within melanocytes [12].

Associations of C05664 with other chemical compounds

• Faster kinetics were observed when Dopa was treated with tyrosinase, the enzyme catalysing the oligomerization of tyrosine to melanins, leading to the formation mainly of DHI oligomers [13].
• In this study we estimate the content of DHICA-derived units in mammalian eumelanins using a combination of two analytical techniques: 1) quantitation of DHICA-derived eumelanin by measuring the yield of pyrrole-2,3,5-tricarboxylic acid (PTCA index) and 2) spectrophotometrical quantitation of total (DHI + DHICA) eumelanin at 350 nm (A350 index) [14].
• Initial potentiometric titrations have been performed on synthetic dihydroxyindole (DHI) melanin solutions to determine the chemical speciation of quinole/quinone subunits [15].

Gene context of C05664

• Melan-si extracts are very efficient in catalyzing dihydroxyindole oxidation, in spite of being heterozygous for the TRP1 mutation, consistent with a stablin effect for the wild-type gp87 protein [16].
• The activity of the insect DI was linear through 15 min incubation, and the amount of DHI produced was proportional to the amount of enzyme that was incorporated into the reaction mixtures [17].
• Addition of catalase to the incubation mixture resulted in a partial removal of DHI inhibition [18].

Analytical, diagnostic and therapeutic context of C05664

• Kinetic and HPLC analyses indicate that both DHI and DHICA are good substrates for this enzymatic system [4].
• The ratio of PTCA/A350 measured for melanins synthesized from DHI and DHICA mixed in various molar proportions correlates well with the content of DHICA in synthetic polymers [14].
• Matrix-assisted laser desorption ionization (MALDI) mass spectrometry of the final pigment provided evidence for homologous series of DHICA oligomers, while chemical analysis allowed an estimate of 2:1 DHICA/DHI-derived units in the polymer, with a substantial proportion of intact o-diphenolic functions [19].

References