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

---

Query: EC:1.10.3.1 (tyrosinase)
9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structures reported for the three cancerostatic all-L-cyclotetrapeptides cyclo(Pro-Leu)2, cyclo(Pro-Val)2 and cyclo(Pro-Phe)2 isolated from a tunicate seem questionable. The synthetic compounds claimed to be identical to the naturally occurring cyclotetrapeptides are in fact not cyclotetrapeptides but rather cyclooctapeptides. We have not been able to prepare the tyrosinase inhibitor cyclo(Pro-Val-Pro-Tyr). Ring closure of H-Pro-Val-Pro-Tyr-OC6F5 gave rise to 31% of cyclo(Pro-Val-Pro-D-Tyr). The same product was obtained in 53% yield from H-Pro-Val-Pro-D-Tyr-OC6F5. For the ring closure to the all-L-cyclopentapeptide cyclo(Pro-Ala-Ala-Phe-Leu), all ring closure positions have been investigated. The reaction at the nitrogen atom of leucine leads to 21% of the all-L-cyclopentapeptide. Dimers or mixtures of monomers and dimers result from reaction at all other positions.
...
PMID:Cyclotetrapeptides and cyclopentapeptides: occurrence and synthesis. 912 2

To identify shared epitopes for melanoma-reactive CTL restricted by MHC molecules other than HLA-A*0201, six human melanoma patient CTL lines expressing HLA-A1 were screened for reactivity against the melanocyte differentiation proteins Pmel-17/gp100, MART-1/Melan-A, and tyrosinase, expressed via recombinant vaccinia virus vectors. CTL from five of the six patients recognized epitopes from tyrosinase, and recognition of HLA-A1+ target cells was strongly correlated with tyrosinase expression. Restriction by HLA-A1 was further demonstrated for two of those tyrosinase-reactive CTL lines. Screening of 119 synthetic tyrosinase peptides with the HLA-A1 binding motif demonstrated that nonamer, decamer, and dodecamer peptides containing the sequence KCDICTDEY (residues 243-251) all reconstituted the CTL epitope in vitro. Epitope reconstitution in vitro required high concentrations of these peptides, which was hypothesized to be a result of spontaneous modification of cysteine residues, interfering with MHC binding. Substitution of serine or alanine for the more N-terminal cysteine prevented modification at that residue and permitted target cell sensitization at peptide concentrations 2 to 3 orders of magnitude lower than that required for the wild-type peptide. Because spontaneous modification of sulfhydryl groups may also occur in vivo, tumor vaccines using this or other cysteine-containing peptides may be improved by amino acid substitutions at cysteine residues.
...
PMID:Human melanoma patients recognize an HLA-A1-restricted CTL epitope from tyrosinase containing two cysteine residues: implications for tumor vaccine development. 949 46

One pathway in forming synaptic-like microvesicles (SLMV) involves direct budding from the plasma membrane, requires adaptor protein 2 (AP2) and is brefeldin A (BFA) resistant. A second route leads from the plasma membrane to an endosomal intermediate from which SLMV bud in a BFA-sensitive, AP3-dependent manner. Because AP3 has been shown to bind to a di-leucine targeting signal in vitro, we have investigated whether this major class of targeting signals is capable of directing protein traffic to SLMV in vivo. We have found that a di-leucine signal within the cytoplasmic tail of human tyrosinase is responsible for the majority of the targeting of HRP-tyrosinase chimeras to SLMV in PC12 cells. Furthermore, we have discovered that a Met-Leu di-hydrophobic motif within the extreme C terminus of synaptotagmin I supports 20% of the SLMV targeting of a CD4-synaptotagmin chimera. All of the traffic to the SLMV mediated by either di-Leu or Met-Leu is BFA sensitive, strongly suggesting a role for AP3 and possibly for an endosomal intermediate in this process. The differential reduction in SLMV targeting for HRP-tyrosinase and CD4-synaptotagmin chimeras by di-alanine substitutions or BFA treatment implies that different proteins use the two routes to the SLMV to differing extents.
...
PMID:Di-leucine signals mediate targeting of tyrosinase and synaptotagmin to synaptic-like microvesicles within PC12 cells. 1056 85

Three types of ferulic acid derivatives (feruloylaminoacid benzyl or methyl esters, feruloylaminoacids, and 4-0-[N-(carbobenzyloxy)-aminoacyl] ferulic acid) were synthesized by introduction of amino acids at different sites and their platelet aggregation (PA)-inhibitory, tyrosinase-inhibitory, angiotensin converting enzyme (ACE)-inhibitory, and superoxide dismutase (SOD)-like activities were evaluated. PA, one of the mechanisms involved in repair of blood vessel injury, is related to diseases such as thrombosis. Developing a compound capable of inhibiting PA may thus provide a therapeutic tool. From the results of study, particularly in the case of 4-0-[N-(carbobenzyloxy) aminoacyl] ferulic acid (amino acid components: isoleucine, proline), inhibition of collagen-induced aggregation was maintained of the same level as with ferulic acid, but stronger dissociation of ADP-induced aggregation was detected. In other words, these compounds may not only prevent thrombosis but also dissolve thrombi. Further, the compounds with stronger tyrosinase-inhibitory activity were found to scavenge superoxide as effectively as ferulic acid. Since they are also more hydrophobic, they may be particularly efficacious as cosmetic ingredients. Finally, feruloyl-Phe-Ala-Pro-OH had strong ACE inhibitory activity (IC50 = 1.5 microM) lacking in the case of ferulic acid itself.
...
PMID:Synthesis and biological activities of ferulic acid derivatives. 1062 55

Several flavonoids, stilbenes and related 4-substituted resorcinols, obtained from Artocarpus incisus and other plants or synthesized, were tested for their inhibitory activity against tyrosinase. The structure-activity relationships suggested that specific natural or synthesized compounds having the 4-substituted resorcinol skeleton have potent tyrosinase inhibitory ability. Kinetic studies have indicated that specific compounds having the 4-substituted resorcinol skeleton exhibit competitive inhibition of the oxidation of DL-beta-(3,4-dihydroxyphenyl)alanine (DL-DOPA) by mushroom tyrosinase. These findings could lead to the design and discovery of new tyrosinase inhibitors.
...
PMID:Inhibition of tyrosinase by flavonoids, stilbenes and related 4-substituted resorcinols: structure-activity investigations. 1070 26

We found a tyrosinase, which has high activity in the presence of organic solvents, in the culture filtrate of Streptomyces sp. REN-21. The organic solvent resistant tyrosinase (OSRT) was purified from the culture filtrate by three column chromatographies. About 1.2 mg of purified OSRT was obtained from 5.6 liters of the culture filtrate with a yield of 26.0%. The purified enzyme had a single polypeptide chain with a molecular mass of about 32,000 Da. The optimum pH and temperature of OSRT were pH 7.0 and 35 degrees C using L-beta-(3,4-dihydroxyphenyl)alanine (L-DOPA) as substrate. OSRT showed stereospecificity toward L-, DL-, and D-enantiomers of DOPA or tyrosine. OSRT had 44% of the activity of the control even in the presence of 50% ethanol, while a mushroom tyrosinase showed only 6% activity under the same conditions. Moreover, OSRT retained its original activity even after 20 h of incubation at 30 degrees C in the presence of 30% ethanol.
...
PMID:An organic solvent resistant tyrosinase from Streptomyces sp. REN-21: purification and characterization. 1073 79

Tyrosinase, with an isoelectric point at pH 4.9, was purified to electrophoretic homogeneity from an extremely thermophilic bacterium, Thermomicrobium roseum. Gel filtration, N-terminal amino acid sequencing and SDS/PAGE analysis indicate that T. roseum tyrosinase is composed of two identical subunits, each with a molecular mass of 43000 Da. The enzyme exhibited high substrate specificity towards catechol, chlorogenic acid, L-3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA) and pyrogallol. The K(m) value of the enzyme for L-DOPA was 0.18 mM. beta-Mercaptoethanol and sodium diethyldithiocarbamate notably inhibited the enzymic activity. The activity of the enzyme was optimal at pH 9.5 and 70 degrees C, and was increased by addition of 1 mM Mg(2+), K(+) or Cu(2+). The enzyme was highly stable against high temperature and guanidine hydrochloride. The N-terminal amino acid sequence of the enzyme was determined to be Asp-Ile-Asn-Gly-Gly-Gly-Ala-Thr-Leu-Pro-Gln-Lys-Leu-Tyr. These facts indicate that T. roseum tyrosinase appears to be distinct from the tyrosinases so far purified from other sources.
...
PMID:Purification and characterization of a highly stable tyrosinase from Thermomicrobium roseum. 1074 56

Mytilus edulis foot protein-1 (mefp1) is a major component of the byssus, an adhesive holdfast in mussels. The recent report of 5, 5'-di(dihydroxyphenyl-L-alanine) (diDOPA) cross-links in byssus [McDowell et al. (1999) J. Biol. Chem. 274, 20293] has raised questions about the relationship of these to mefp1. About 80% of the primary structure of mefp1 consists of a tandemly repeated consensus sequence Ala(1)-Lys(2)-Pro(3)-Ser(4)-Tyr(5)-Pro(6)-Pro(7)-Thr(8)-Tyr(9)-Lys(10 ) with varying degrees of posttranslational hydroxylation to hydroxyprolines in positions 3, 6, and 7 and to DOPA in positions 5 and 9. Six natural or synthetic variants of this decapeptide were subjected to oxidation by tyrosinase or periodate. DOPA is the only residue to suffer losses in all oxidized peptides. Moreover, using MALDI TOF mass spectrometry, oxidized decapeptides all showed evidence of multimer formation and a mass loss of 6 Da per coupled pair of peptides. Multimer formation was inhibited by addition of DOPA-like o-diphenols, but addition of simple amines such as free Lys had no effect. The results are consistent with aryloxy coupling to diDOPA followed by reoxidation to diDOPA quinone. There are subtle but noteworthy variations, however, in multimer formation among the peptide congeners. Decapeptides with Pro(3) modified to trans-4-hydroxyproline do not form multimers beyond dimers; they also exhibit significant Lys losses following oxidation of DOPA. Moreover, in Ala-Lys-Hyp-Ser-Tyr-DiHyp-Hyp-Thr-DOPA-Lys, Tyr appears to be protected from oxidation by tyrosinase.
...
PMID:Cross-linking in adhesive quinoproteins: studies with model decapeptides. 1099 54

Tyrosine residues of neuroendocrine peptides are frequently the targets of oxidation reactions, one of which involves hydroxylation to peptidyl-3, 4-dihydroxy-phenyl-L-alanine (DOPA). The reactivity in vitro of peptidyl-DOPA in two neuroendocrine peptides, a neurotensin fragment (pELYENK) and proctolin (RYLPT), was investigated using ultraviolet-visible scanning spectrophotometry and matrix-assisted laser desorption ionization mass spectrometry following oxidation by tyrosinase and periodate. The peptides form covalently coupled dimers and trimers, and their masses are consistent with the presence of diDOPA cross-links. Lysine does not appear to participate in multimer formation because it is efficiently recovered in fragmentation ladders using subtilisin. While multimer formation in the neurotensin-derived peptide can be blocked effectively by adding N-acetyl-DOPA-ethylester to the reaction medium, the DOPA ethylester couples itself four to five times to each peptide.
...
PMID:Reactivity of peptidyl-tyrosine to hydroxylation and cross-linking. 1127 64

Polyphenol levels in wines are affected by the wine-making process. Resveratrol is one polyphenol which has been the subject of a commendable amount of recent research. In this work, we found that resveratrol is immediately degraded by tyrosinase. A novel tyrosinase was purified from Carignan grapes. The purification process included salting out and separation on a cation-exchange column, followed by gel filtration. Tyrosinase was purified in a homogeneous form by SDS-PAGE and was characterized: its specific activity toward 3-(3,4-dihydroxyphenyl)-L-alanine (DOPA) increased by a factor of 24 with an overall recovery of 3% of initial activity. The apparent molecular mass of the purified tyrosinase was 40 kDa as determined by SDS-PAGE, and 42 kDa as determined by gel filtration. Its activity was optimal at pH 6 and at 25 degrees C. The enzyme exhibited high activity toward phenylenediamine, epicatechin, pyrogallol, DOPA, and resveratrol. Tyrosinase activity was inhibited by KCN, thiourea, and SO(2). Resveratrol levels were stable following the removal of proteins from the juice, suggesting that early spraying of grapes with SO(2) is an important factor affecting the final amount of resveratrol in wine.
...
PMID:Resveratrol and a novel tyrosinase in Carignan grape juice. 1131 83


<< Previous 1 2 3 4 5 6 7 8 Next >>

---