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)

Some effects of light on morphogenesis in Sclerotium rolfsii Sacc. were studied. Physiological competence to visible light developed during the first 120 h after inoculation, with an optimum sensitivity phase between 84 and 96 h that coincided with the leading hyphae reaching the edge of the Petri dish. Although sclerotial initials were produced in dark-grown cultures, light was necessary for the continuation of the developmental and maturation phases of sclerotial morphogenesis. Tyrosinase activity (o-diphenol: oxygen oxidoreductase, EC 1.10.3.1) was detected during sclerotial formation and the pH and temperature optima for his polyphenol oxidase in vitro were about 6.0 and 45 degrees C respectively. The enzyme was inhibited by cysteine. Similar activity levels of tyrosinase were obtained in blue and "white" light-grown cultures but in red light activity was comparable with that of dark-grown cultures. Laccase activity was not detected at any stage of development.
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PMID:The effects of light and tyrosinase during sclerotium development in Sclerotium rolfsii Sacc. 1 16

Hair follicle tyrosinase levels and melanin content, together with serum tyrosine levels have been studied in relation to annual pelage color changes in the Siberian hamster. Tyrosinase levels were found to peak not only at the spring moult when pigmented hair is produced but also at the autumn moult when the hair produced is unpigmented. The melanin content of hair follicles was high in summer and low in winter but serum tyrosine levels did not differ at the spring and autumn moults. These results suggest that some factor must exist to prevent the raised tyrosinase levels of the autumn moult being expressed as melanogenesis and that this factor must be photoperiodically modifiable, being controlled through a neuroendocrine mechanism.
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PMID:Pelage color cycles and hair follicle tyrosinase activity in the Siberian hamster. 10 97

Tyrosinase activity decreases as the reaction proceeds and is inhibited by L-3,4-dihydroxyphenylalanine oxidation products. Indole and tryptophan inhibit tyrosinase reaction and bovine albumin protects against end-product(s) inhibition or inactivation. Since the same tyrosinase reaction products are indole compounds and some authors reported the binding of indole derivatives with albumin, it is here suggested that indole intermediates of melanin synthesis inhibit or inactivate tyrosinase.
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PMID:Inhibition of tyrosinase by indole compounds and reaction products. Protection by albumin. 11 28

An immunoassay for tyrosinase, using the modified bacteriophage technique, was developed: Tyrosinase of Neurospora was conjugated to bacteriophage T4 using glutaraldehyde as a cross-linking agent. The conjugated phage that survived the coupling process could be inactivated by antiserum raised in rabbits against pure tyrosinase, but not by normal serum. This inactivation was specifically inhibited by pure Neurospora tyrosinase, and the degree of inhibition was proportional to the concentration of tyrosinase within the range of 30-150 ng/ml. Crude mycelial extract possessing tyrosinase activity could similarly inhibit the inactivation of the conjugated phage by the antiserum. To evaluate the tyrosinase content of crude extracts their inhibitory capacity was compared to that of known amounts of pure tyrosinase, and the amounts thus calculated agreed with those predicted from an enzymatic assay. The tyrosinase-bacteriophage immunoassay was used for the quantitation of tyrosinase-antigen in crude extracts of Neurospora cultures that had been induced to form tyrosinase by the addition of ethionine. Enzymatic activity appeared after a lag of several hours, increased for 2-3days and then declined. Immunological assays of these cultures showed: (a) serologically reactive protein started to accumulate upon culture starvation and was evident during the lag period; (b) specific activity (units per mg antigen) was constant throughout induction; (c) at the phase of decrease in mycelial enzyme content, increasing amounts of serologically reactive protein were detected in the medium, indicating that some enzyme was eventually excreted. These results show that the lag is not a qualitatively distinct period, and support the previously forwarded notion that tyrosinase is synthesized de novo upon induction.
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PMID:Immunochemical studies on tyrosinase induction in Neurospora. 12 53

A human melanoma cell line established in our laboratory was characterized in terms of tyrosinase activity and anionic polysaccharide production. Tyrosinase levels were diluted during the growth phase and increased after the cell culture became confluent. The anionic polysaccharides produced included hyaluronic acid, heparitin sulfate, and a high-molecular-weight condroitin 4-sulfate. In contrast, a primary culture of human melanocytes derived from embryonic iris produced much greater amounts of hyaluronic acid, about 30-fold less heparitin sulfate, and a mixture of chondroitin 4-sulfate and dermatan sulfate. Saccharides secreted into the culture medium were generally identical to those remaining cell associated except for the melanoma heparitin sulfate, wherein the latter fraction appeared to be of lower molecular weight.
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PMID:Anionic polysaccharide production and tyrosinase activation in cultured human melanoma cells. 13 Sep 71

Purified melanosomes isolated from subcutaneously growting Harding-Passey melanomas of NMRI-mice were labeled either in vitro with [14C]tyrosine or [14C]DOPA in the melanin portion, or in vivo in the melanin and protein portion following i. p. injection of [14C]tyrosine. Treatment of monolayer cultures of Harding-Passey melanoma cells (HPM-73 line) with such labeled melanosomes resulted in rapid uptake of label during the first 4 h which leveled off thereafter. A portion of the "incorporated" label could be removed by a 15 min chase with unlabeled melanosomes. Uptake of labeled melanosomes by HPM-73 cells was followed by increased cellular melanization which was not only due to melanin derived from incorporated melanosomes but primarily to newly formed melanin. Tyrosinase activity was elevated in melanosome-treated cells. Tyrosinase activity of control cells was significantly reduced following a 24 h exposure to actinomycin D or cycloheximide. On the other side, the same inhibitor treatment of melanosome-pretreated cells resulted in less inhibition of tyrosinase activity. The present findings suggest "melanophagic" properties of cultured melanoma cells resulting in enhanced melanogenesis after phagocytotic uptake of functionally active exogenous melanosomes.
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PMID:Enhanced melanization of Harding-Passey mouse melanoma cells following treatment with exogenous melanosomes in monolayer culture. 15 42

Tyrosinase was first detected in melanoblasts by the DOPA-oxidase reaction in the presence of catalase in explants of goldfish integument after 12 hr culture with either ACTH (1IU/ml) or DB-cAMP (0.1mM). Melanin did not appear in the new melanocytes until 24 hr. The data indicate that the release of cAMP within the melanoblast in response to ACTH treatment is rapid and the tyrosinase in the melanoblast is released from inhibition and/or activated at least 12 hr prior to melanization of premelanosomes.
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PMID:In vitro induction of tyrosinase activity in goldfish (Carassius auratus L.) integument by ACTH and dibutyryl-cAMP. 17 39

A variant of B-16 F1 mouse melanoma was selected for its ability to survive and replicate in the presence of melanocyte-stimulating hormone (MSH). Although the variant (MR-4) was completely resistant to growth inhibition of MSH, cyclic AMP was still able to block cell replication. Tyrosinase activity in MR-4 cells was considerably lower than in B-16 F1 cells. MSH induced a two fold to three-fold increase in tyrosinase activity in both cell types, but the absolute activity in MR-4 remained significantly less than in the parental cells. MR-4 cells were also found to have a markedly depressed cyclic AMP-dependent protein kinase activity relative to B-16 F1 cells. The protein kinase from both cell types was stimulated by cyclic AMP, but the level of MR-4 kinase activity at maximal cyclic AMP concentrations remained considerably lower than B-16 F1 kinase activity under the same conditions. In both cell types adenylate cyclase activity was markedly stimulated by MSH. When equal numbers of viable F1 and MR-4 cells were injected subcutaneously into C57/B1 mice, the MR-4 cells formed tumors earlier and killed the host sooner than the parental F1 cells. We conclude that the biochemical alteration which allows MR-4 cells to replicate in the presence of MSH is a low level of tyrosinase activity, which in turn may be the result of low cyclic AMP-dependent protein kinase activity.
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PMID:Isolation and characterization of a variant of B16-mouse melanoma resistant to MSH growth inhibition. 23 92

The tapetum lucidum of the alligator gar Lepisosteus was shown by t.l.c. to contain a new phenolic amino acid, which is apparently a major constituent of the reflecting material. It was isolated in a yield of 0.5 mg/eye and its physical and chemical characteristics, especially reductive hydrolysis with hydriodic acid giving dopa (3,4-dihydroxyphenylalanine) and cysteine, suggested that it might to SS-dicysteinyldopa. Tyrosinase oxidation of L-dopa in the presence of an excess of L-cysteine yielded, in addition to known 5- and 2-S-cysteinyldopa, the same amino acid as that isolated from the eye of the gar, thus confirming the gross structure. The position of the two cysteine residues was established by the fact that tyrosinase oxidation of catechol and cyteine gave 3-S-cysteinylcatechol and 3,6-SS-dicysteinylcatechol. The natural amino acid is therefore formulated as 3-(2,5-SS-dicysteinyl-3,4-dihydroxyphenyl)alanine (2,5-SS-dicysteinyldopa), which may be formed by two consecutive additions of cysteine, first to dopaquinone and then to 5-S-cysteinyldopaquinone. The enzymic synthesis of 2,5-SS-dicysteinyldopa in vitro suggests that it may also be involved in the biosynthesis of phaeomelanin.
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PMID:A new amino acid, 3-(2,5-SS-dicysteinyl-3,4-dihydroxyphenyl)alanine, from the tapetum lucidum of the gar (Lepisosteidae) and its enzymic synthesis. 40 9

Ultrastructural studies, and cytochemical and biochemical determinations of tyrosinase activity were conducted on the pigment epithelium of albino and xanthic goldfish eyes. In eyes of xanthic goldfish, two types of melanosomes are present, spherical and elongated. Melanized melanosomes are absent in the eyes of the albino goldfish, but elongated lamellar premelanosomes are observed. Internal vesicles are present in both melanosome types in the pigment epithelium of the xanthic goldfish but are absent in premelanosomes of the albino. There are also differences in the distribution of lipid droplets, smooth endoplasmic reticulum and Golgi complexes with the latter two being more abundant in the albino. Tyrosinase was not identified cytochemically; however, the enzyme was demonstrated biochemically in the pigment epithelia of both albino and xanthic goldfish. The enzyme is associated with the particulate and soluble fractions fo both types of eyes. Particulate albino tyrosinase may be solubilized by triton X-100 treatment. Tyrosinase inhibitors are present in the particulate fractions of both albino and xanthic goldfish eyes. Thus, in the goldfish, ocular albinism appears to be a multiple defect at the molecular and ultrastructural levels.
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PMID:Trysinase positive oculocutaneous albinism in the goldfish, Carassius auratus l., and ultrastructural and biochemical study of the eye. 41 72


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