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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The gene from Streptomyces glaucescens coding for an inducible tyrosinase was cloned using the low copy vector pIJ41 and the melanin-negative strain Streptomyces lividans TK23 as host. Hybridisation experiments as well as complementation studies showed that melC mutant strains carry large deletions of more than 10.5 kb, comprising the structural gene for tyrosinase, while melA and melB strains carry mutations in genes involved in the expression of tyrosinase activity. Strong DNA homology was found between the Streptomyces antibioticus and the S. glaucescens tyrosinase structural genes and both genes showed a similar regulation when introduced into melanin-negative hosts. While both tyrosinases exhibited clear induction in S. glaucescens, constitutive expression was observed in S. lividans. Northern blot experiments showed that tyrosinase expression is regulated at the transcriptional level and that the gene (822 bp) is part of a 2.3 kb transcript. The main start of the mRNA at about 475 bp upstream from the tyrosinase N-terminus was located by S1-mapping experiments.
Mol Gen Genet 1985
PMID:Cloning and expression of the genetically unstable tyrosinase structural gene from Streptomyces glaucescens. 299 65

The Rhizobium leguminosarum biovar phaseoli symbiotic plasmid pRP2JI carries a gene, melA, specifying the enzyme tyrosinase, which is responsible for the production of the pigment melanin in these bacteria. Transcription of melA is activated by the nifA gene of Rhizobium and, when the cloned melA gene is transferred to Escherichia coli, melA is expressed if the recipients contain nifA gene of Klebsiella pneumoniae. This nifA-dependent activation was temperature sensitive and required the ntrA gene. The cloned nifA gene of K. pneumoniae, when transferred to a nifA mutant of Rhizobium phaseoli biovar phaseoli, corrected the Mel- but not the Fix- phenotype. nifA of R. leguminosarum biovar phaseoli activated melA at higher levels in cells grown in low concentrations of oxygen. Also, nifA of R. leguminosarum biovar phaseoli activated nifH of K. pneumoniae in Escherichia coli cells grown in low-oxygen concentrations.
Mol Microbiol 1988 May
PMID:Transcription of a Rhizobium leguminosarum biovar phaseoli gene needed for melanin synthesis is activated by nifA of Rhizobium and Klebsiella pneumoniae. 304 Dec 40

The identification of possible copper ligands in human ceruloplasmin was carried out by the computer similarity analysis for sequences of ceruloplasmin and several other copper oxidases: azurin, plastocyanin, superoxide dismutase, tyrosinase and hemocyanin. It follows from the analysis of inter- and intramolecular homology that copper active sites of different types appeared to be in close contacts within the ceruloplasmin molecule.
Mol Biol (Mosk)
PMID:[Localization of active sites in human ceruloplasmin from data of intra- and intermolecular homology]. 365 83

The results of studies on genetic control of resistance to antibiotics in Streptomyces strains are discussed. Cloning and sequence analysis of resistance genes yield information concerning their expression in homo- and heterologous systems, allow analysis of signal sequences responsible for initiation of transcription and translation. Cloning of genes coding for resistance to neomycin,viomycin, thiostrepton in Streptomyces and Bac. licheniformis ermD gene made them convenient selective markers for constructing vector molecules, useful for identification of homology regions in S. fradiae aph gene and TnS of E. coli; the site homologous to ermD gene has been thus revealed in S. erythreus chromosome. Possibilities of the studies aimed at elucidation of instability of many actinomycete characters using determinants of natural multiple resistance to antibiotics as a model are demonstrated. It has been shown that genetic instability is not related to the loss of plasmids and is associated with genes having chromosomal location. Simultaneous high frequency loss of a number of resistance characters determined by non-linked genes suggests the participation in gene activity regulation of actinomycete genome rearrangements. This is confirmed by evidence for such rearrangements found in strains with mutant phenotypes, including deletions in tyrosinase and streptomycin phosphotransferase genes in Mel- and StrS strains of S. reticuli and S. glaucescens.
Mol Gen Mikrobiol Virusol 1985 Mar
PMID:[Genetic control of Actinomycetes resistance to antibiotics]. 391 22

alpha-Melanocyte-stimulating hormone (alpha-MSH, alpha-melanotropin), [Nle4,D-Phe7]-alpha-MSH and related fragment analogues, Ac-[Nle4,D-Phe7]-alpha-MSH4-11-NH2 and Ac-[Nle4,D-Phe7]-alpha-MSH4-10-NH2, were studied for their ability to stimulate tyrosinase activity in Cloudman S91 mouse melanoma cells in tissue culture. All of the melanotropins stimulated tyrosinase activity in a dose-dependent manner. [Nle4,D-Phe7]-alpha-MSH was about 100 times more active than alpha-MSH as determined from the minimal effective dose (MED) required to activate the enzyme above control (basal) levels. The MED of this analogue to significantly stimulate tyrosinase activity at 24, 48 and 72 h of incubation was 10(-11) M whereas the MED of alpha-MSH was 10(-9) M at each of these times. The maximum tyrosinase activity achieved from the time of initial incubation in the presence of [Nle4,D-Phe7]-alpha-MSH was approximately 3-, 5- and 6-fold greater than control levels at 24, 48 and 72 h, respectively. The 2 [Nle4,D-Phe7]-substituted fragment analogues were at least as active as the tridecapeptide analogue and therefore at least 100-fold more active than alpha-MSH in stimulating enzyme activity. These [Nle4,D-Phe7]-substituted analogues were more active in the melanoma tyrosinase assay than in the melanoma adenylate cyclase assay or other normal melanocyte (frog and lizard skin) bioassays.
Mol Cell Endocrinol 1985 Jul
PMID:Stimulation of S91 melanoma tyrosinase activity by superpotent alpha-melanotropins. 392 59

The influence of vitamin D nutrition on melanogenesis in skin induced by UV radiation was studied in pigmented adult rats. Melanogenesis, assessed by the activity of skin tyrosinase (radiometric assay), was studied in vitamin-D-deficient and vitamin-D-fed rats exposed to UV (0.1 J/cm2, 290-320 nm). The tyrosinase activity in skin was not significantly changed by vitamin D treatment alone. In contrast, the induction of tyrosinase activity provoked by UV radiation was greater in vitamin-D-fed than in vitamin-D-deficient rats. The increase in skin tyrosinase activity in response to UV was preceded by an increase in skin cAMP levels. This rise in cAMP was greater in vitamin-D-treated rats than in vitamin-D-deficient rats. The pretreatment of rats with phosphodiesterase inhibitor potentiated the effect of vitamin D on skin tyrosinase activity. The low serum calcium levels in the vitamin-D-deficient group were evidently not responsible for the lower UV induction of skin tyrosinase activity because the vitamin-D-deficient rats with normal serum calcium levels (supplemented with 20% lactose and 2% calcium in the diet) were also unable to show maximal induction of skin tyrosinase activity in response to UV radiation requires the presence of adequate vitamin D. cAMP may be involved in the mediation of this effect. The relationship observed between the vitamin D status of animals and tyrosinase activity of skin could provide an effective feed-back control for protection against UV and vitamin D intoxication.
Mol Cell Endocrinol 1982 Mar
PMID:Vitamin D nutrition increases skin tyrosinase response to exposure to ultraviolet radiation. 617 46

Tyrosinase is a copper containing monooxygenase catalyzing the formation of melanin pigments and other polyphenolic compounds from various phenols. This review deals with the recent progress on the molecular structure of the enzyme from Neurospora crassa and the unique features of the binuclear active site copper complex involved in the activation of molecular oxygen and the binding of substrates. The results of the spectroscopic properties of Neurospora tyrosinase will also be discussed in the light of the structural similarity of the copper complex in the oxygen binding hemocyanins.
Mol Cell Biochem 1983
PMID:Neurospora tyrosinase: structural, spectroscopic and catalytic properties. 630 14

The sporulating wild type of Streptomyces reticuli produces the pigment melanin. Though the ability to synthesize tyrosinase is frequently lost, it was demonstrated, that the structural gene coding for this enzyme is not located on the extrachromosomal DNA of the wild type strain or melanin-positive variants. Melanin negative variants were found to have lost this gene and to contain amplified nucleotide sequences within their genomes.
Mol Gen Genet 1983
PMID:Deletion and amplification of DNA sequences in melanin-negative variants of Streptomyces reticuli. 640 51

The actual cellular target of the cytotoxic intermediates of melanin synthesis is not yet known. In the present paper it is shown that eukaryotic DNA binds in vitro to soluble reaction products of tyrosinase (EC 1.14.18.1) and is physically modified, as ascertained by the following criteria: (a) buoyant density in cesium chloride density gradients; (b) polyacrylamide gel electrophoresis; (c) deoxyribonuclease (EC 3.1.4.5) test; (d) electron microscopy. The results reported here support the view that DNA itself may be a target for the cytotoxic intermediates of melanin synthesis.
Mol Gen Genet 1984
PMID:Possible genotoxicity of melanin synthesis intermediates: tyrosinase reaction products interact with DNA in vitro. 642 31

Tetrahydropapaveroline (THP) oxidation was studied in various experimental conditions by absorbance spectroscopy. THP was found to be easily oxidized by mushroom tyrosinase, giving rise to the formation of a chromophore (THP-chrome) with absorption maxima at 308 and 470 nm. The oxidation further proceeds leading to the formation of a melanin-like pigment. The use of periodate as oxidant at pH 7.4 allows the visualization of the THP-chrome, as well. Other tetrahydroisoquinolines bearing a catechol moiety, such as salsolinol, laudanosoline and apomorphine, have been found to be easily oxidized in the same conditions, giving rise to pigmented derivatives. The products of THP oxidation are able to copolymerize with dopa or opioid peptides in the presence of tyrosinase, generating mixed-type melanins.
Biochem Mol Biol Int 1995 May
PMID:Production of melanin pigments by chemical and enzymatic oxidation of tetrahydroisoquinolines. 749 63


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