Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Retinoic acid, hexamethylene bisacetamide, sodium butyrate, and dimethylsulfoxide, four compounds which modulate phenotypic expression in a variety of neoplastic cell lines, all inhibited the induction of tyrosinase activity and melanogenesis by the combination of melanocyte-stimulating hormone and isobutylmethyxanthine in Cloudman S91 melanoma cells. Results were the same in assays of whole cells or in extracts made from them. Only retinoic acid, however, was effective at inhibiting the activation of dopachrome isomerase, another regulatory enzyme in melanogenesis. Despite inhibiting the effects of melanocyte-stimulating hormone (MSH) and isobutylmethylxanthine on tyrosinase activity, all of the agents tested increased the binding of MSH to intact cells. Ultrastructural analysis of treated cells following DOPA cytochemistry revealed that both retinoic acid and hexamethylene bisacetamide arrested melanosomal maturation at stage I-II. Retinoic acid resulted in a derangement of melanosomal structure. The specificity of these agents for preventing the induction of melanogenesis makes them powerful tools for the dissection of this complex cellular process.
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PMID:Inhibition of induced melanogenesis in Cloudman melanoma cells by four phenotypic modifiers. 170 21

Dopachrome isomerase, which mediates the conversion of dopachrome to dihydroxyindoles, is an enzyme affiliated with the melanogenic pathway found in most vertebrates and invertebrates. We have recently reported an activity-staining procedure for detecting this enzyme after electrophoresis on tyrosinease-embedded polyacrylamide gels using dopa [K. Nellaiappan, G. Nicklas, and M. Sugumaran, (1994) Anal. Biochem. 220, 122-128]. The usefulness of this method is limited to the availability of good quality of tyrosinase. To overcome the limitations of nonavailability as well as batch to batch variation in the specific activity of commercially available tyrosinase which will affect the staining, we have developed a new stain technique using chemically made dopachrome for the detection of dopachrome isomerase. The new method employs the use of dopachrome generated in situ by the oxidation of dopa with periodate. Dopachrome isomerase initially appears as a bluish-purple (melanochrome) band against an orange-red background. Eventual transformation of melanochrome to dark insoluble melanin polymer produces a black band corresponding to dopachrome isomerase activity. Continuous washing of the gel clears the background. Usefulness of this technique to stain dopachrome isomerase (a) in different organisms and (b) on polyacrylamide gels, agarose gels, and nitrocellulose membranes is demonstrated. In addition, conditions to stain the enzyme on nitrocellulose membranes using mushroom tyrosinase are described. Comparison of the effectiveness of tyrosinase versus periodate staining procedure reveals that the former method is superior to the latter in detecting dopachrome isomerase. The periodate method overcomes the problems associated with the quality of commercially available tyrosinase and its nonavailability in certain regions.
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PMID:Detection of dopachrome isomerase on gels and membranes. 750 14

Dopachrome isomerase is a recently discovered enzyme associated with the melanogenesis process occurring in most vertebrates and invertebrates. It catalyzes the conversion of dopachrome to 5,6-dihydroxyindole(s). Based on the fact that 5,6-dihydroxyindoles are rapidly oxidized to melanochrome pigment by tyrosinases, we have developed a rapid, sensitive, and specific staining procedure for detection of dopachrome isomerase activity after gel electrophoresis. The method employs the use of commercially available mushroom tyrosinase entrapped in polyacrylamide gels for electrophoretic separation of dopachrome isomerase. Staining is achieved by the use of dopa solution. The dopachrome formed by the action of mushroom tyrosinase entrapped in the gel is converted to 5,6-dihydroxyindole(s) by dopachrome isomerase initially. The latter compound is subsequently oxidized by tyrosinase to purple-colored melanochrome. Therefore, dopachrome isomerase appears as a bluish-purple band against a pale orange-red background within 10 min. With the use of the new detection technique, the presence of hitherto unknown isozymes of dopachrome isomerase could be readily detected in polyacrylamide gels. This procedure is more sensitive than silver staining for detection of dopachrome isomerase and as little as 15 ng of purified protein could be easily detected on gels.
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PMID:Detection of dopachrome isomerase activity on gels. 752 30

Melanogenesis in animals is initiated by tyrosinase and augmented by recently discovered dopachrome isomerase. Mushroom tyrosinase embedded 5% polyacrylamide gels are used to specifically stain for dopachrome isomerase activity after electrophoretic separation. Using this new procedure, the ontogenic changes in dopachrome isomerase are demonstrated for the first time in any organism. While there is no isozyme variation within the same stage of development, there are profound variations in isozyme patterns during the developmental stages from egg to adult, indicating differential expression and/or processing of dopachrome isomerase genes to match the metabolic needs at these stages.
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PMID:The ontogeny of dopachrome isomerase isozyme patterns in the tobacco hornworm Manduca sexta. 817 84

Melanin biosynthesis in animals is initiated by the ubiquitously present tyrosinase and is aided by dopachrome isomerase. We have characterized a novel dopachrome isomerase (decarboxylating) from the hemolymph of Manduca sexta that generates a new quinone methide intermediate during melanogenesis (Sugumaran, M. and Semensi, V. (1991) J. Biol. Chem. 266, 6073-6078). This enzyme has the ability to form a complex with mushroom tyrosinase as judged by a number of physicochemical studies. The isomerase exhibited a marked inhibitory effect on tyrosinase and tyrosinase reciprocated by inhibiting the isomerase. While the isomerase showed no activity toward preformed dopaminechrome, it readily influenced the stability of dopaminechrome generated in situ by tyrosinase. Moreover, mushroom tyrosinase, which lacked specific binding to Concanavalin A Sepharose column, after complexing with the isomerase exhibited binding to this column. The complex formation also affected the pI value as well as mobility on a size exclusion column of these enzymes. Enzymes executing sequential metabolic transformation are known to form complexes called metabolons. Based on these above studies, it is concluded that both the enzymes involved in insect melanogenic pathway--phenoloxidase and dopachrome isomerase--are able to form a metabolon complex.
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PMID:Complex formation between mushroom tyrosinase and Manduca dopachrome isomerase. 861 68

Melanogenesis involves oxidation of 3,4-dihydroxyphenylalanine (dopa) to dopachrome which then is converted into 5,6-dihydroxyindole by dopachrome isomerase. 5,6-Dihydroxyindole is oxidized to its quinone which in turn is metabolized nonenzymatically to melanin. In addition to dopachrome isomerase, a new dopminechrome isomerase activity involved in the conversion of dopaminechrome into 5,6-dihydroxyindole has been observed in the larva of Rhinoceros oryctes. This dopaminechrome isomerase differs from dopachrome isomerase in its electrophoretic mobility and substrate specificity. The present study reports a specific, sensitive and rapid staining method for detecting dopaminechrome isomerase activity after electrophoresis. Using this new method, the presence of the dopaminechrome isomerase activity, which is involved in melanogenesis, could easily be detected by staining tyrosinase embedded native gels in dopamine solution. Tyrosinase entrapped in the gels converts dopamine in dopaminechrome. The dopaminechrome isomerase separated in the gels catalyzes dopaminechrome to 5,6-dihydroxyindole which is oxidized further by tyrosinase to colored melanochrome. The dopaminechrome isomerase appears as a bluish purple band against a pink background.
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PMID:A method for detecting dopaminechrome isomerase activity on gels. 1055 61

Tyrosinase initiates melanogenesis in a variety of organisms. The nature of melanin formed is modified subsequently by dopachrome isomerase and other melanogenic proteins. Earlier, we reported the partial purification of dopachrome isomerase (decarboxylating) from the hemolymph of Manduca sexta and demonstrated the generation of a new quinone methide intermediate during melanogenesis (Sugumaran, M., and Semensi, V. (1991) J. Biol. Chem. 266, 6073-6078). In this paper, we report the purification of this enzyme to homogeneity and a novel inhibition mechanism for regulation of phenoloxidase activity. The activity of phenoloxidase isolated from M. sexta was markedly inhibited by purified dopachrome isomerase. In turn, phenoloxidase also reciprocated by inhibiting the isomerase activity. Preformed dopaminechrome did not serve as the substrate for the isomerase; but dopaminechrome that generated in situ by phenoloxidase was readily converted to melanin pigment by the phenoloxidase/isomerase mixture. Furthermore, the isomerase, which has a molecular weight of about 40,000 in native state, exhibited retardation during affinity electrophoresis on sodium dodeyl sulfate (SDS)-polyacrylamide gel electrophoresis gel copolymerized with tyrosinase and migrated with a molecular weight of 50,000, indicating complex formation with phenoloxidase. Electrophoresis of pupal cuticular extract on polyacrylamide gel, followed by activity staining revealed the presence of a protein band carrying both phenoloxidase and isomerase activity. Accordingly, a high-molecular-weight melanogenic complex was isolated from the pharate cuticle of M. sexta. The complex catalyzed the generation of melanochrome from dopa, while the free phenoloxidase produced only dopachrome from the same substrate. When the complex was treated with trace amounts of SDS, which inhibited the activity of dopachrome isomerase present in the complex, then only the conversion of dopa to dopachrome was observed. These studies confirm the formation of a melanogenic complex between phenoloxidase and dopachrome isomerase. By forming a complex and regulating each other's activity, these two enzymes seem to control the levels of endogenous quinones.
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PMID:Insect melanogenesis. III. Metabolon formation in the melanogenic pathway-regulation of phenoloxidase activityy by endogenous dopachrome isomerase (decarboxylating) from Manduca sexta. 1086 May 57

The phenolic biopolymer eumelanin is an important skin pigment found throughout the animal kingdom. The enzyme, tyrosinase, initiates melanogenesis in mammals. The biogenesis is assisted by a number of mammalian protein factors including dopachrome tautomerase and 5,6-dihydroxyindole-2-carboxylate oxidase. Invertebrates, such as insects, employ phenoloxidase and dopachrome (decarboxylating) isomerase for melanin biosynthesis. Recently generated molecular biological and biochemical data indicate that tyrosinase and phenoloxidase are distinctly different enzymes in spite of possessing both monophenol monooxygenase activity as well as o-diphenoloxidase activity. Similarly, insect dopachrome isomerase also differs significantly from its mammalian counterpart in several of its properties including the nature of the enzymatic reaction. In addition, there are considerable differences in the eumelanogenic pathways of these two animal groups that include the utility of substrates, use of dihydroxyindoles and the nature of eumelanin pigment. Thus, the biochemistry and molecular biology of melanogenesis in mammals and insects are significantly different. The advantages of generating different eumelanin pigments and intermediates by the insects are discussed.
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PMID:Comparative biochemistry of eumelanogenesis and the protective roles of phenoloxidase and melanin in insects. 1183 52