Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

We have used a probe derived from TRP-2/DT to detect migratory melanoblasts shortly after they emerge from the neural crest, as early as 10 days post coitum (dpc). TRP-2/DT expression is otherwise restricted to the presumptive pigmented retinal epithelium, the developing telencephalon and the endolymphatic duct. The pattern of steel and c-kit hybridisation in the developing brain differed from that of TRP-2. TRP-1 and tyrosinase probes also detected melanoblasts but were both expressed later in development than TRP-2. We used the TRP-2/DT probe to investigate the way that the Steel-dickie (Sld) mutation interferes with melanocyte development, and found that the membrane-bound steel growth factor which is missing in Sld/Sld mutants is necessary for the survival of melanoblasts but not for their early migration and initial differentiation.
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PMID:TRP-2/DT, a new early melanoblast marker, shows that steel growth factor (c-kit ligand) is a survival factor. 128 May 58

Tyrosinase is synthesized on membrane-bound ribosomes and transported into melanosomes through smooth endoplasmic reticulum and Golgi apparatus. Melanin polymers are produced only in melanosomes but never in smooth endoplasmic reticulum or Golgi apparatus, indicating that posttranslational modifications of tyrosinase are completed with melanosomes where tyrosinase becomes an active form. Based on a working hypothesis that tyrosinase-positive oculocutaneous albinism is a consequence of the structurally altered tyrosinase due to a point mutation in the gene of its gene coding for a glycosylation site or a membrane-binding site, which leads to the impairment in the posttranslational modification of tyrosinase and its catalytic activity, we have cloned the tyrosinase gene of one patient affected with tyrosinase-positive oculocutaneous albinism and determined its nucleotide sequence. Thus demonstrated all exons' nucleotide sequence of the patient's tyrosinase gene was found to be identical to that of the wild-type gene. The results indicate that the patient's tyrosinase itself is not altered. We therefore propose that the molecular basis for the development of tyrosinase-positive oculocutaneous albinism exists as a defect in other proteins required for the activation of tyrosinase or in other regions of the tyrosinase gene.
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PMID:Cloning and sequence analysis of the tyrosinase gene from a patient with tyrosinase-positive oculocutaneous albinism. 149 98

Three enzymes (acid phosphatase, peroxidase, and tyrosinase) were localized by electron microscopy within the retina of crayfish Orconectes limosus. Peroxidase activity was observed only in lamellar bodies, which are secondary lysosomes and degrade photosensory membrane. After H2O2 was omitted from the reaction medium, peroxidase activity in lamellar bodies was partly inhibited but was not missing completely. After addition of sodium pyruvate, which inhibits endogenous generation of H2O2, staining of lamellar bodies was absent. Tyrosinase activity was found in lamellar bodies and in small vesicles within the rhabdoms similar to those found positive for acid phosphatase. Granules (500-700 nm in diameter) with an electron opaque matrix and mature screening pigment granules showed tyrosinase activity. Moreover, lamellar structures within membrane-bound organelles that additionally contained screening pigment-like granules were electron dense because of tyrosinase activity. After addition of phenylthiourea (PTU) to the incubation medium, lamellar bodies did not generally contain electron dense deposits, although weak staining of single membranes still was sometimes observed. After addition of sodium pyruvate in combination with PTU, no staining was detected. The possible role of tyrosinase in ommochrome synthesis within secondary lysosomes that degrade photosensory membrane is discussed.
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PMID:Peroxidase and tyrosinase are present in secondary lysosomes that degrade photosensory membranes of the crayfish photoreceptor: possible role in pigment granule formation. 166 20

Sodium butyrate (butyrate), 5-azacytidine (5Aza-C), dimethyl sulfoxide (DMSO), and dimethyl formamide (DMF) were applied to a human melanoma cell line for the purpose of inducing pigmentation and terminal differentiation. The results are summarized as follows: 1) butyrate, DMSO, and DMF had a strong cytostatic effect, arresting cells in the G1 phase of the cycle; 2) butyrate caused a morphological change to spindle shape whereas DMSO and DMF produced rounded cells, without affecting the levels of vimentin and intermediate filaments; 3) tyrosinase activity and melanization were stimulated by DMSO and DMF but not by butyrate; 4) butyrate induced several membrane-bound enzyme activities (alkaline phosphatase and gamma-glutamyl transpeptidase); 5) changes in the expression of antigens related to tyrosinase activity (2B7 and 5C12) only partly corresponded to the changes in enzyme activity; 6) expression of the melanosomal B8G3 antigen was decreased by butyrate, DMSO, and DMF; and 7) the action of DMF resembled that of DMSO whereas 5Aza-C had little effect. The results indicate that these differentiating agents activate different sets of genes, the melanogenic pathway being activated independently of gamma-glutamyltranspeptidase. The down regulation of B8G3 antigen by these agents may provide a common focus for understanding the essential action of differentiation inducers in melanoma cells.
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PMID:In vitro phenotypic alteration of human melanoma cells induced by differentiating agents: heterogeneous effects on cellular growth and morphology, enzymatic activity, and antigenic expression. 171 Mar 61

Rat liver microsomes contain a membrane-bound GSH S-transferase (GSH-tr), an enzyme that is involved in the detoxication of xenobiotics. Also located on rat liver microsomes is the cytochrome P450 system, an enzyme complex that catalyzes the conversion of several xenobiotics into reactive intermediates. In this study, it was demonstrated that reactive products from alpha-methyldopa formed by the cytochrome P450 system are able to stimulate microsomal GSH-tr. Also, products formed from alpha-methyldopa that are generated by H2O2-horseradish peroxidase and tyrosinase are able to stimulate the activity of microsomal GSH-tr. GSH was able to prevent the activation of microsomal GSH-tr. Our results indicate that the ortho-quinone or semi-ortho-quinone radical of alpha-methyldopa is responsible for the stimulation of microsomal GSH-tr, probably via arylation of the free sulfhydryl group of microsomal GSH-tr. This conclusion was supported by the observation that 4-methyl-ortho-quinone itself was able to stimulate microsomal GSH-tr via sulfhydryl arylation. Our results are in conformity with the hypothesis that reactive products formed by the cytochrome P450 complex are able to stimulate microsomal GSH-tr and possibly in this way enhance their detoxication.
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PMID:Activation of the microsomal glutathione S-transferase by metabolites of alpha-methyldopa. 189 94

3T3 Swiss mouse fibroblast cell lines expressing tyrosinase, the critical enzyme in melanin synthesis, have been established by co-transfection of a mouse tyrosinase cDNA and a G418-resistance gene. Of sixty-three clones isolated, four are brown in colour, presumably due to synthesis of melanin. Expression of both the tyrosine hydroxylase and dopa oxidase activities of tyrosinase by these pigmented clones has been demonstrated directly by enzyme assays. Electron microscopic studies suggest that the brown pigment is located in membrane-bound cytoplasmic vesicles.
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PMID:Expression of a mouse tyrosinase cDNA in 3T3 Swiss mouse fibroblasts. 190 37

Triton X-114 was used to partially purify broad bean polyphenol oxidase, a thylakoid membrane-bound enzyme, in latent form, free of phenolic compounds and chlorophylls, with a high recovery rate. The activation of the latent enzyme by detergents or trypsin was 10 times higher than that obtained when the enzyme was purified by other methods used in plant biochemistry, such as acetone powders and ammonium sulfate fractionation. The kinetic parameters of the latent and activated enzyme are also given.
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PMID:Partial purification of a thylakoid-bound enzyme using temperature-induced phase partitioning. 210 49

In order to clarify the biologic significance of carbohydrate processing in tyrosinases for melanogenesis, we have studied the effect of differential carbohydrate processing inhibitors on the recovery process of interrupted melanization which occurs after exposure of cultured B-16 melanoma cells to the inhibitor of core carbohydrate synthesis, glucosamine (Glc). Treatment of this glycosylation-dependent repigmentation process with the early-stage carbohydrate processing inhibitors deoxynojirimycin (dNM), castanospermine (CS), and monensin (MS) at 0.8 mM, 40 micrograms/ml, and 30 nM, respectively, in the presence of 2 mM theophylline (Tp) almost completely inhibits the reappearance of the pigment 48-72 h after removal of Glc. In contrast, treatment with the later stage carbohydrate processing inhibitor swaisonine (SW) at 40-80 micrograms/ml does not interrupt the repigmentation process. Electrophoretic analysis of tyrosinases in the soluble fractions of these melanoma cells demonstrates that the alteration of soluble tyrosinase isozymes by all the processing inhibitors is associated with a dose-dependent loss of sialic acid-rich T1 tyrosinase and the concomitant appearance or increase of sialic acid-poor tyrosinases. In the large granule fraction, a recovery of membrane-bound tyrosinase (T3) is seen following both MS and SW treatments, whereas dNM treatment results in the substantial loss of T3 tyrosinase. At the electron microscopic level, a translocation of tyrosinase from GERL and coated vesicles to many unmelanized vacuolar premelanosomes occurs in MS-treated cells in contrast to its predominant distribution in the GERL-coated vesicle system of dNM-treated cells, which contain many unmelanized premelanosomes. The present evidence for differential effects on intracellular tyrosinase transfer and melanization by different stages of carbohydrate processing inhibition suggests that asparagine-linked oligosaccharides, relating to the first mannose-trimming stages, determine the function of tyrosinase transfer as well as melanization through a specific intracellular recognition process in pigment cells.
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PMID:Analysis of carbohydrate properties essential for melanogenesis in tyrosinases of cultured malignant melanoma cells by differential carbohydrate processing inhibition. 211 51

The murine b locus encodes the tyrosinase related protein, TRP-1, a putative membrane-bound, copper-containing enzyme having about 40% amino acid identity with tyrosinase. The protein is essential for production of black rather than brown hair pigment. We show that skin of mutant brown mice contains the same amount of TRP-1 mRNA as wild type. On sequencing the coding region of the mutant mRNA we find four nucleotide differences from the wild-type (Black) sequence. Two of these differences result in different amino acid residues encoded by the brown allele. By sequencing the TRP-1 gene from a mouse in which a reversion from brown to Black has been induced by ethylnitrosourea we are able to show that only one of these amino acid changes, which substitutes a tyrosine for a conserved cysteine, is the cause of the brown phenotype. This mutation is adjacent to another cysteine at which, in the analogous position in tyrosinase a mutation results in the albino phenotype. The sequence of the revertant is the first report of DNA sequence of an ethylnitrosourea-induced genetic change in mouse.
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PMID:The molecular basis of brown, an old mouse mutation, and of an induced revertant to wild type. 224 16

The Glycosylation inhibitors, glucosamine or tunicamycin induced a marked loss of pigment within melanoma cells in addition to their reduced metastatic ability. Electrophoresis of tyrosinase demonstrated the disappearance of or a marked decrease in membrane-bound tyrosinase, T3 in the small and large-granule fractions. Glycoprotein synthesis in the melanogenic subcellular compartments of pigment cells seems to play an integral role in melanogenesis which is principally enhanced in their carcinogenic status. The effect of interferon (IFN) on melanoma metastasis was investigated using B16-F10 melanoma cells. The inhibitory effect was maximal when given 3 h prior to tumor cell inoculation. IFN given 12 and 24 h prior to, as well as simultaneously with, tumor cell inoculation, also reduced metastases, but to a lesser extent. When given 2 h after the inoculation, no effect was shown. The salutary effect of IFN was abolished by anti-asialo GMI, but NK activity was enhanced equally throughout 3 to 24 hrs. This indicates that the effect is substantially dependent on NK cell activity, although the implication of other factors is not excluded.
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PMID:[Control of melanogenesis by glycosylation inhibitors and the inhibitory effect of interferon on melanoma metastasis]. 240 78


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