نتایج جستجو برای: tyrosinase
تعداد نتایج: 3872 فیلتر نتایج به سال:
Mammalian tyrosinase as currently defined has two catalytic functions: 1) the oxidation of tyrosine to L-3,4-dihydroxyphenylalanine (dopa) and 2) the oxidation of dopa to dopa quinone (1-9). Although an imposing body of evidence has been advanced in support of this interpretation, Okun and associates have recently challenged the prevailing concept of the action of tyrosinase ( 10, 11 ). They ha...
A precursor form of Neurospora crassa tyrosinase has been identified by Western transfer from crude protein extracts and by immunoprecipitation of in vitro translated tyrosinase mRNA. The molecular weight of protyrosinase (75,000) exceeds that of mature tyrosinase (46,000) by about 50%. In order to deduce the primary structure and the nature of the extension, the tyrosinase gene was cloned. Pol...
Tyrosinase activity was demonstrated in the sera from melanoma-bearing mice. One, two, and three weeks following tumor transplantation, 12, 80, and 90% of the respective sera from these mice showed positive results. No sera from normal mice had tyrosinase activity. There was a correlation between tumor size and tyrosinase activity, the coefficient of correlation being 0.71. The activity in the ...
In melanocytes and in melanoma cells, upregulation of melanogenesis, by cAMP elevating agents, results from a stimulation of tyrosinase activity that has been ascribed to an increase in tyrosinase protein and messenger amount. However, the mechanism by which cAMP elevating agents increase tyrosinase mRNA remains to be elucidated. In this study, using a luciferase reporter plasmid containing the...
The human tyrosinase gene codes for two distinct antigens that are recognized by HLA-A*0201-restricted CTLs. For one of them, tyrosinase peptide 368-376, the sequence identified by mass spectrometry in melanoma cell eluates differs from the gene-encoded sequence as a result of posttranslational modification of amino acid residue 370 (asparagine to aspartic acid). Here, we used fluorescent tetra...
The human tyrosinase-derived peptide YMDGTMSQV is presented on the surface of human histocompatibility leukocyte antigen (HLA)-A*0201(+) melanomas and has been suggested to be a tumor antigen despite the fact that tyrosinase is also expressed in melanocytes. To gain information about immunoreactivity and self-tolerance to this antigen, we established a model using the murine tyrosinase-derived ...
Tyrosinase is a key player in ultraviolet-induced melanogenesis. Because excessive melanin accumulation in the skin can induce hyperpigmentation, the development of tyrosinase inhibitors has attracted attention in cosmetic-related fields. However, side effects including toxicity and low selectivity have limited the use of many tyrosinase inhibitors in cosmetics. We synthesized 12 novel 2-(subst...
licles pigmentation in mammals. Melanin biosynthesis or melanogenesis occurs in specialized organelles, called melanosomes, through a cascade of enzymatic reactions using the amino acid tyrosine as the initial substrate. The first two steps in the biosynthetic pathway, hydroxylation of tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) and oxidation of L-DOPA to dopaquinone, are catalyzed by tyr...
Background: Mushroom Tyrosinase a potent candidate in clinical studies known as polyphenol oxidase, is a metaloenzyme from the oxidase superfamily widely distributed from lower to higher life forms. It plays a crucial role in sclerotization of exoskeleton in insects, also responsible for skin pigmentation in mammalians. Objective: In this study, after reconstitution of MT by some metal io...
Modern techniques offer an opportunity for a more complete evaluation of melanin production in the uvea and retinal pigment epithelium (RPE). By measuring the release of tritium from tritiated tyrosine in homogenized samples of adult bovine RPE as well as iris and choroid, tyrosinase activity could be demonstrated in both the uveal tract and the RPE. Phenylthiourea, a specific tyrosinase inhibi...
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