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)

The reaction products of peroxidase, a hydrogen donor and hydrogen peroxide decreased the amount of lysine recovered from proteins after acid hydrolysis. Oxidation of peroxidase treated proteins with performic acid prior to hydrolysis formed alpha-amino adipic acid indicating that the peroxidase or the quinones formed by peroxidase had oxidatively deaminated some lysyl residues of the protein to form lysyl aldehyde. Gel filtration and polyacrylamide gel electrophoresis revealed dimers, trimers and higher protein polymers that were not detected when peroxidase was omitted. Since some of the protein polymers were not dissociated by gel electrophoresis in the presence of dodecyl sulfate, urea and mercaptoethanol, it suggests that the free radicals or quinones formed by peroxidase had interacted with or cross-linked protein molecules by the formation of covalent bonds. Oxidative enzymes like peroxidase and polyphenol oxidase may lower the nutritive value of proteins by the oxidative deamination of lysine, reaction with cysteine and methionine and by cross-linking protein molecules to reduce their susceptibility to enzymatic hydrolysis.
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PMID:Cross-linking of protein by peroxidase. 2 Jul 49

Our previous studies have shown that 4-S-cysteaminylphenol (4-S-CAP) causes a significant inhibition of in vivo melanoma growth and a marked depigmentation of black skin and hair follicles. These studies have suggested a role of tyrosinase in the manifestation of these in vivo effects. In this study 4-S-CAP and its analogues were examined for their effects on the growth of human melanoma cells in vitro. 4-S-CAP and 4-S-HomoCAP exhibited strong cytotoxicity with effects much greater than those of alpha-methyl-4-S-CAP and N,N-dimethyl-4-S-CAP. The cytotoxicity of the former two amines was completely prevented by semicarbazide, an inhibitor of plasma monoamine oxidase, while that of the latter two was not prevented by semicarbazide, catalase, and phenylthiourea, a tyrosinase inhibitor. In culture medium 4-S-CAP was rapidly converted by the action of monoamine oxidase present in fetal bovine serum to the aldehyde which was then metabolized to the alcohol and the carboxylic acid when cells were present. alpha-Methyl-4-S-CAP was found to exert higher cytotoxicity to cells with higher tyrosinase activity and melanin content. These results suggest that the in vitro cytotoxicity of 4-S-CAP and 4-S-HomoCAP is mediated through conversion to the aldehydes while that of alpha-methyl-4-S-CAP appears to be dependent on tyrosinase activity to some extent.
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PMID:Mechanism of growth inhibition of melanoma cells by 4-S-cysteaminylphenol and its analogues. 210 82

In this study, melanophore cytodifferentiation in the fins of xanthic goldfish that had been exposed to osmotic stress for 18 days was investigated. It was found that multi-vesicular bodies (MVB) are not the only type of premelanosome. Granules having a homogeneous matrix also function as premelanosomes. The presence of acid phosphatase reaction product inside the melanin granules indicated that these organelles in this animal were also related to lysosomes. DOPA-oxidase of tyrosinase, the key enzyme in melanogenesis, was surprisingly not only detected in melanocytes but also in the Golgi stacks of dermal cells. Due to the mechanisms of premelanosome formation it is evident that cytoplasmic material also serves as substrate for melanogenesis. EDX microanalysis was performed to measure the ionic composition of the melanin granules. After aldehyde fixation the newly-formed melanin granules did not contain Na, but had accumulated Ca.
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PMID:Heterogeneous ultrastructure of melanosome formation in the goldfish induced by osmotic stress. 886 53

Leaves of the privet tree, Ligustrum obtusifolium, contain a large amount of oleuropein, a phenolic secoiridoid glycoside, which is stably kept in a compartment separate from activating enzymes. When the leaf tissue is destroyed by herbivores, enzymes localized in organelles start to activate oleuropein into a very strong protein denaturant that has protein-crosslinking and lysine-decreasing activities. These activities are stronger than ever reported from plant systems and have adverse effects against herbivores by decreasing the nutritive value of dietary protein completely. We report here that strong oleuropein-specific beta-glucosidase in organelles activates oleuropein by converting the secoiridoid glucoside moiety of oleuropein into a glutaraldehyde-like structure, which is also an alpha,beta-unsaturated aldehyde. Oleuropein activated by beta-glucosidase had very strong protein-denaturing, protein-crosslinking, and lysine-alkylating activities that are very similar to, but stronger than, those of glutaraldehyde. Aucubin, another iridoid glycoside, had similar activities after beta-glucosidase treatment. We also detected polyphenol oxidase activity in organelles that activate the dihydroxyphenolic moiety to have protein-crosslinking activities. These data suggest that the privet tree has developed an effective defense mechanism with oleuropein, a unique multivalent alkylator ideal as a protein-crosslinker. Our results that iridoid glycosides are precursors of alkylators may elucidate the chemical bases that underlie various bioactivities and ecological roles of iridoid glycosides.
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PMID:Enzymatic activation of oleuropein: a protein crosslinker used as a chemical defense in the privet tree. 1043 Sep 12

The inhibition of mushroom tyrosinase by Pulsatilla cernua root-derived materials was evaluated. The bioactive components of Pulsatilla cernua root were characterized by spectroscopic analyses as 3,4-dihydroxycinnamic acid and 4-hydroxy-3-methoxycinnamic acid, which exhibited potent antityrosinase activity. The ID50 values of 3,4-dihydroxycinnamic acid and 4-hydroxy-3-methoxycinnamic acid were 0.97 and 0.33 mM, respectively. The compounds isolated from Pulsatilla cernua roots exhibited noncompetitive inhibition against oxidation of L-DOPA by mushroom tyrosinase. This activity was compared with that of three cinnamic acid derivatives and four well-known tyrosinase inhibitors. The ID50 of 4-hydroxy-3-methoxycinnamic acid exhibited superior activity relative to anisaldehyde, anisic acid, benzoic acid, benzaldehyde, cinnamic acid, and cinnamaldehyde; but antityrosinase inhibitors and cinnamic acid derivatives, except for cinnamyl alcohol, were slightly more effective than 3,4-dihydroxycinnamic acid. In the case of benzaldehyde and cinnamaldehyde, the aldehyde group is, apparently, a key group in eliciting potent inhibitory activity, whereas anisaldehyde is more effective than anisic acid. Methoxy substitutions, such as 2-methoxycinnamic acid, 3-methoxycinnamic acid, and 4-methoxycinnamic acid, enhanced inhibition of tyrosinase activity. As a naturally occurring tyrosinase inhibitor, 3,4-dihydroxycinnamic acid and 4-hydroxy-3-methoxycinnamic acid may be useful as new agents to inhibit the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase.
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PMID:Tyrosinase inhibitors of Pulsatilla cernua root-derived materials. 1187 10

Tetrahydroisoquinolines (TIQs) are endogenous alkaloid compounds deriving from the non-enzymatic Pictet-Spengler condensation of catecholamines with aldehydes. These compounds are able to unsettle catecholamines uptake and release from synaptosomes and have been detected in urine and in post-mortem Parkinsonian brains. We have obtained in vitro, by the reaction of dopa-enkephalin (dopa-Gly-Gly-Phe-Leu) with acetaldehyde in the presence of rameic ions, a TIQ derivative of Leu-enkephalin. The isolation and the recovery of the peptide was obtained by HPLC. The acid hydrolysis and the subsequent analysis of the peptide lysate by the Amino acid analyser clearly revealed the absence of dopa, while the electrospray ionisation mass spectrometry showed that the sequence of the enkephalin derivative was the following: 3-carboxy-salsolinol-Gly-Gly-Phe-Leu (TIQ-enkephalin). This compound was not a good substrate for microsomal aminopeptidase and pronase with respect to Leu-enkephalin. Tested in the binding assay, the TIQ-enkephalin exhibited a very poor affinity toward the enkephalin receptors. When the TIQ-enkephalin was incubated with tyrosinase or peroxidase/H(2)O(2), the formation of TIQ-opio-melanins occurred.
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PMID:Tetrahydroisoquinoline derivatives of enkephalins: synthesis and properties. 1203 73

Graphite electrodes fabricated by screen-printing have been used as amperometric detectors in biosensors based on NAD(+)-dependent dehydrogenases, tyrosinase, or genetically modified acetylcholinesterases. The mono-enzyme sensors have been optimized as disposable or reusable devices for detection of a variety of substrates important in the food industry ( D-lactic acid, L-lactic acid, acetaldehyde) or in environmental pollution control (phenols and dithiocarbamate, carbamate and organophosphorus pesticides). The sensors were prepared in four configurations differing in enzyme confinement, enzyme immobilization and location of the immobilization agent in the biosensor assembly. Tests on real samples have been performed with the biosensors; D-lactic acid and acetaldehyde have been detected in wine and phenols in air.
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PMID:Biosensors designed for environmental and food quality control based on screen-printed graphite electrodes with different configurations. 1220 36

Copper is next to iron the most important element in the biological transport, storage and in redox reactions of dioxygen. A bioanalogous activation of dioxygen with copper complexes is used for catalytical epoxidation, allylic hydroxylation and oxidative coupling of aromatic substrates, for example. With stereochemical information in form of chiral ligands, enantioselective reactions may be possible. Another aspect of interest on copper catalyzed reactions with dioxygen is that the exact mechanism and biological function of some enzymes (especially catechol oxidase) is yet not fully clear. For studies mimicking the copper-containing catechol oxidase appropriate chiral steroid ligands with defined stereochemistry and conformation have been synthesized. The four diastereomeric 16,17-aminoalcohols of the 3-methoxy-estra-1,3,5(10)-triene series have been condensed with salicylic aldehyde and different beta-ketoenols to the chiral ligand types 1-5. These compounds with different steric and electronic properties and different arrangements of the neighboring hydroxy and nitrogen functions were reacted with copper(II) acetate to copper complexes. The structure of these complexes will be discussed. The bioanalogous oxidation of 3,5-di-tbutyl-catechol (dtbc) to the corresponding quinone was catalyzed by most of the complexes, indicating their ability to activate dioxygen. The trans configurations c and d showed an activity one magnitude higher than the cis configurations a and b. Comparing compounds with the same diastereomeric configuration, the main influence was that of the peripheral R(1-3) substituents at the beta-ketoenaminic group which are useful for the fine-tuning of the properties of the copper atoms like redox potential and Lewis acidity.
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PMID:Synthesis, structure and catechol-oxidase activity of copper(II) complexes of 17-hydroxy-16-(N-3-oxo-prop-1-enyl)amino steroids. 1223 Nov 19

To synthesize glycyrrhetinic acid (GA) derivatives (3, 4, 5, 10, 13, 14, 15, and 16), we first removed the ketonic group in the C-11 position, and the carboxylic function at the C-30 position was kept intact, reduced to an alcohol, or transformed to an aldehyde corresponding derivatives 10 and 13. Glycyrrhetinic acid (GA) derivatives (3, 4, 5, 15, and 16) were coupled with 4-amino piperpyridine derivatives (12 and 14) and 4-fluorobenzyl bromide at C-30 carboxylic acid position of glycyrrhetinic acid. In subsequent tyrosinase assays, we found that GA derivatives 4, 5, and 16 were not active at early time points, but strongly inhibited tyrosinase activity at late time points. Of the GA derivatives examined, derivative 5 was most active, with an IC(50) value of 50 microM after 2 h reaction. IC(50) values of derivatives 4 and 16 were 120 and 170 microM, respectively. Further kinetic data indicated that these derivatives are slow-binding inhibitors of tyrosinase. The time-dependent inhibition was reversed when vitamin C or kojic acid was used, that is, both compounds showed active inhibition at early time points. These results suggest that GA derivatives are much more stable than vitamin C or kojic acid, although their intrinsic inhibitory potentials are relatively low. Higher stability and activity suggest that GA derivative 5 might be a useful candidate for skin whitening.
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PMID:Synthesis of new glycyrrhetinic acid (GA) derivatives and their effects on tyrosinase activity. 1464 78

The inhibition of mushroom tyrosinase by cucumber extracts was evaluated. The inhibitory effect was measured by both polarographic and spectrophotometric methods. The commercial aldehyde, trans,cis-2,6-nonadienal, described as a major volatile compound of cucumber, was characterized as a noncompetitive inhibitor against 4-tert-butylcatechol oxidation by mushroom tyrosinase. The K(I) obtained was 3.4 mM. Polyphenol oxidase (PPO) activity was not detected in cucumber skin extracts. However, the presence of PPO was revealed by Western blot; a single band was found with a M(r) of 53 kDa. These results support the assumption that the enzyme PPO is present in the cucumber skin, but its activity is inhibited. Peroxidase (PO) was also found in cucumber skin extracts. This enzyme was detected in the soluble fraction but not in the membrane fraction. The kinetic characterization of PO was carried out. Native isoelectric focusing revealed several acidic PO isoenzymes with a pI in the range between 5 and 6, a basic isoenzyme, and one principal neutral isoenzyme of pI = 7.2.
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PMID:Tyrosinase inhibitory activity of cucumber compounds: enzymes responsible for browning in cucumber. 1466 42


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