Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Synthetic lysinoalanine (LAL) may be a more effective inhibitor of the zinc-containing enzyme carboxypeptidase A than is ethylenediamine tetraacetic acid (EDTA). The enzyme is also inactivated by alkali-treated, lysinoalanine-containing food proteins such as casein, high-lysine corn protein, lactalbumin, soy protein isolate, and wheat gluten, and by alkali-treated zein, which contains no lysinoalanine. Zinc sulfate regenerates only part of the enzymatic activity after exposure to the treated proteins. The extent of inhibition increases with protein concentration and time of treatment. Any inhibition due to phytate is distinct from that due to the treatment. Phenylethylaminoalanine (PEAA), derived from biogenic phenylethylamine, inhibited enzymatic activity of the metalloenzyme carboxypeptidase A (CPA). The inhibition was maximal at pH 7.0 in the pH range 7 to 8.5. The extent of inhibition increased with time of treatment and PEAA concentration. N-acetyl-PEAA did not inhibit the enzyme, suggesting that the free alpha-NH2 group is required for inhibition. PEAA, LAL, sodium phytate, and cysteine also inactivated the copper enzyme, polyphenol, oxidase (tyrosinase) which plays a major role in enzymatic (oxidative) browning of foods. Analogous comparative studies with LAL, EDTA, and sodium phytate suggest that the potency of PEAA as an inhibitor of CPA is similar to that of sodium phytate, and that of the four compounds tested, PEAA is least effective against tyrosinase. Related studies of the iron and copper containing enzyme cytochrome C oxidase showed that EDTA was not inhibitory, PEAA was slightly inhibitory, and LAL and sodium phytate were stronger inhibitors. Mechanistic explanations are offered to account for some of these observations. The possible relevance of these findings to in vivo protein digestion, enzymatic (oxidative) browning of foods, and the mechanism of the lysinoalanine effect on kidney cells are also discussed.
 ...
PMID:Inactivation of metalloenzymes by lysinoalanine, phenylethylaminoalanine, alkali-treated food proteins, and sulfur amino acids. 302 44

The stability of tryptophan was evaluated in several different food model systems using a chemical method (high pressure liquid chromatography after alkaline-hydrolysis) and rat assays. Losses of tryptophan were compared with the losses of lysine and methionine. Whey proteins stored in the presence of oxidizing lipids showed large losses of lysine and extensive methionine oxidation but only minor losses of tryptophan as measured chemically. The observed decrease in bioavailable tryptophan was explained by a lower protein digestibility. Casein treated with hydrogen peroxide to oxidize all methionine to methionine sulphoxide showed a 9% loss in bioavailable tryptophan. When casein was reacted with caffeic acid at pH 7 in the presence of monophenol monooxygenase (tyrosinase; EC 1.14.18.1), no chemical loss of tryptophan occurred, although fluorodinitrobenzene-reactive lysine fell by 23%. Tryptophan bioavailability fell 15%, partly due to an 8% reduction in protein digestibility. Alkali-treated casein (0.15 M-sodium hydroxide, 80 degrees, 4 h) did not support rat growth. Chemically-determined tryptophan, available tryptophan and true nitrogen digestibility fell 10, 46 and 23% respectively. Racemization of tryptophan was found to be 10% (D/(D+L)). In whole-milk powder, which had undergone "early' or "advanced' Maillard reactions, tryptophan, determined chemically or in rat assays, was virtually unchanged. Extensive lysine losses occurred. It was concluded that losses of tryptophan during food processing and storage are small and of only minor nutritional importance, especially when compared with much larger losses of lysine and the more extensive oxidation of methionine.
 ...
PMID:Stability of tryptophan during food processing and storage. 1. Comparative losses of tryptophan, lysine and methionine in different model systems. 393 49

The chemical and enzymatic browning reactions of plant polyphenols and their effects on amino acids and proteins are reviewed. A model system of casein and oxidizing caffeic acid has been studied in more detail. The effects of pH, time, caffeic acid level and the presence or not of tyrosinase on the decrease of FDNB-reactive lysine are described. The chemical loss of lysine, methionine and tryptophan and the change in the bioavailability of these amino acids to rats has been evaluated in two systems: pH 7.0 with tyrosinase and pH 10.0 without tyrosinase. At pH 10.0, reactive lysine was more reduced. At pH 7.0 plus tyrosinase methionine was more extensively oxidized to its sulphoxide. Tryptophan was not chemically reduced under either condition. At pH 10.0 there was a decrease in the protein digestibility which was responsible for a corresponding reduction in tryptophan availability and partly responsible for lower methionine availability. Metabolic transit of casein labelled with tritiated lysine treated under the same conditions indicated that the lower lysine availability in rats was due to a lower digestibility of the lysine-caffeoquinone complexes.
 ...
PMID:Nutritional consequences of the reactions between proteins and oxidized polyphenolic acids. 649 20

1. Studies were made on the lysine content of casein reacted with caffeic acid oxidized aerobically under alkaline conditions of enzymically with tyrosinase (EC 1. 14. 18. 1). 2. Loss of fluorodinitrobenzene (FDNB)-reactive lysine was rapid at pH 10 and increased with time and the temperature of the reaction, with concentration of caffeic acid and with the oxygenation of the mixture. In presence of the enzyme mushroom tyrosinase, maximum reduction of reactive lysine occurred at pH 7 and was dependent on the reaction time and on the concentration of caffeic acid. 3. Reaction of alpha-formyl-LO-[U-14C]lysine with caffeic acid at pH 10 showed the rapid formation of five reaction products which appeared to polymerize gradually as the reaction progressed. 4. The nutritionally available lysine content of the casein-caffeic acid mixtures, as assayed with rats, was reduced after both alkaline and enzyme reactions, as were faecal digestibility, net protein ratio and net protein utilization. Biological value however was not reduced. 5. In metabolic studies using goat milk casein labelled with L-[3H]lysine and reacted with caffeic acid in the same way, the lysine-caffeoquinone reaction products were not absorbed by the rat but were excreted directly in the faeces. 6. The importance of the reaction of proteins with caffeoquinone and chlorogenoquinone (formed by the oxidation of caffeic and chlorogenic acids respectively) is discussed in relation to the production of sunflower protein, leaf protein and other vegetable-protein concentrates.
 ...
PMID:Protein-polyphenol reactions. 1. Nutritional and metabolic consequences of the reaction between oxidized caffeic acid and the lysine residues of casein. 680 76

The effects of bovine milk proteins on melanogenesis in B16 cells were examined. Both whey protein isolate and casein exhibited depigmenting properties. Among the major protein components of milk--including beta-lactoglobulin, alpha-lactalbumin, alpha-, beta-, and kappa-casein--only kappa-casein exhibited the depigmenting effect. However, the carboxyl terminal peptide of kappa-casein, glycomacropeptide, did not show this activity. Also, kappa-casein promoted the proliferation of the cells and inhibited the activity of tyrosinase in the cells. These results indicate that kappa-casein acts as a melanogenesis-suppressing modulator.
 ...
PMID:Kappa-casein suppresses melanogenesis in cultured pigment cells. 901 9

Tyrosinase was used to initiate the grafting of peptides onto the amine-containing polysaccharide chitosan. Chemical evidence for covalent grafting was obtained from electrospray mass spectrometry for products formed from reactions with glucosamine (the monomeric unit of chitosan) and the model dipeptide Tyr-Ala. When this model dipeptide was incubated with tyrosinase and chitosan, there was a marked increase in the viscosity of the solution. This viscosity increase provides physical evidence that tyrosinase can initiate peptide grafting onto the chitosan backbone. A peptide-modified chitosan derivative was generated by reacting chitosan (0.32 w/v%) with acid-hydrolyzed casein (0.5 w/v %) using tyrosinase. After reaction, the peptide-modified chitosan was partially purified and dissolved in an aqueous acetic acid solution. Low concentrations of this peptide-modified chitosan were observed to confer viscoelastic properties to the solutions. Specifically they conferred high viscosities and shear thinning properties to the solutions, and solutions containing only 1 w/w % of the peptide-modified chitosan behaved as weak gels. Thus, tyrosinase provides a simple and safe way to convert food-processing byproducts into environmentally friendly products that offer useful functional properties. The selectivity of tyrosinase and the relatively high reactivity of chitosan's amines allow grafting to be performed with uncharacterized peptide mixtures present in crude hydrolysates.
 ...
PMID:Enzymatic grafting of peptides from casein hydrolysate to chitosan. Potential for value-added byproducts from food-processing wastes. 1496 32

The three extant peccary species, the Chacoan (Catagonus wagneri), the White-lipped (Tayassu pecari) and the Collared (Pecari tajacu), are morphologically and chromosomally distinct and confined to the New World. There is ongoing paleontological, cytogenetic, and molecular debate about phylogenetic relationships among them. To contribute to the understanding of Tayassuidae phylogeny, three mitochondrial (control region, cytochrome b, and 12S rRNA) and five nuclear (K-casein, thyrotropin, tyrosinase, and swine short interspersed nuclear elements PRE-1 P27 and P642) peccary DNA fragments were amplified, cloned and sequenced from Chacoan, White-lipped, and Collared peccaries. Phylogenetic analyses were performed using maximum likelihood and neighbor joining methods. K-casein, thyrotropin, and tyrosinase sequences did not resolve the phylogeny, while control region, cytochrome b, 12S rRNA, and PRE-1 P27 and P642 sequences were more informative in deciphering phylogenetic relationships. When pig and warthog were used as an outgroup, Chacoan and White-lipped peccaries clustered distinct from Collared peccaries. Furthermore, control region and cytochrome b sequence variation within Collared peccaries was as extreme as that between White-lipped and Chacoan peccaries, supporting subspecific and possibly even specific variation within the widely distributed Collared peccary. This study supports the existence of two independent genera within the Tayassuidae family consisting of Collared and Chacoan/White-lipped peccaries, in contrast with classical morphological taxonomy which clusters White-lipped and Collared peccaries in the genus Tayassu or which alternatively clusters the Collared peccary in the genus Dicotyles as a related sister clade of the Chacoan peccary (genus Catagonus).
 ...
PMID:Nuclear and mitochondrial evolutionary analyses of Collared, White-lipped, and Chacoan peccaries (Tayassuidae). 1557 91

An organic solvent-resistant tyrosinase (OSRT) from Streptomyces sp. REN-21 is a unique enzyme showing high activity in the presence of organic solvents. The OSRT-catalyzed oxidation of monophenols such as tyrosine-containing peptides and proteins was examined. The catalytic properties of OSRT were compared with those of mushroom tyrosinase. OSRT was shown to oxidize Gly-l-Tyr most effectively among four peptide substrates tested. On the other hand, mushroom tyrosinase showed the highest activity toward l-Tyr-Gly under the condition of 1 mM substrate. OSRT oxidized several proteins, including casein and hemoglobin, with relatively higher activity compared with mushroom tyrosinase under the condition of 1% (w/v) substrate. Thus, it was clarified that the catalytic properties of OSRT toward tyrosine-containing peptides and proteins are different from those of mushroom tyrosinase under these conditions. The OSRT-encoding gene operon was cloned, and found to consist of two genes, designated ORF-OSRT and ORF-393. The former encodes apo-OSRT, and the latter encodes the putative activator protein of apo-OSRT. A binuclear copper-binding site (type-3 copper site) characteristic of tyrosinases is contained in the deduced amino acid sequence for apo-OSRT. A high-level production system for the OSRT was constructed using pET20b(+) and Escherichia coli BL21(DE3)pLysS. Approximately 54 mg of active OSRT was synthesized in a 1-liter broth culture by this system. The properties of the recombinant OSRT were similar to those of the wild-type enzyme. In conclusion, we succeeded in constructing a high-level production system for OSRT.
 ...
PMID:Catalytic properties of an organic solvent-resistant tyrosinase from Streptomyces sp. REN-21 and its high-level production in E. coli. 1627 29

Proteins and certain carbohydrates contain phenolic moieties, which are potential sites for modification of the function of the biopolymers. In this study, the capability of two different fungal oxidative enzymes, laccase from Trametes hirsuta (ThL) and tyrosinase from Trichoderma reesei (TrT), to catalyze formation of hetero-cross-linking between tyrosine side chains of alpha-casein and phenolic acids of hydrolyzed oat spelt xylan (hOSX) was studied. Formation of reaction products was followed by size exclusion chromatography (SEC), fluorescence spectroscopy, and SDS-PAGE, using specific staining methods for proteins and protein-carbohydrate conjugates. ThL and TrT were observed to differ significantly in their ability to catalyze the formation of protein-carbohydrate conjugates or the linking of the small molecular weight phenolic compounds to alpha-casein. The efficiency of these enzymes to directly cross-link protein also differed notably. TrT was able to cross-link alpha-casein more efficiently than ThL. ThL-catalyzed casein cross-linking was significantly enhanced by ferulic acid, p-coumaric acid, and also hOSX. The main reaction products by ThL appeared to be phenolic acid-bridged alpha-caseins. Indications of hetero-cross-link formation between alpha-casein and hOSX by both oxidative enzymes could be visualized by glycoprotein-specific staining in the SDS-PAGE analysis, although ThL was observed to be more effective in the heteroconjugate formation than TrT.
 ...
PMID:Formation of protein-oligosaccharide conjugates by laccase and tyrosinase. 1842 26

This paper reports on the cross-linking and immobilisation of various proteins by the recombinant tyrosinase from Verrucomicrobium spinosum (Vs-tyrosinase). In general it is found that Vs-tyrosinase can readily cross-link proteins with a low degree of complexity, such as casein, but that the enzyme cannot readily cross-link well folded protein substrates such as lysozyme, myoglobin, cytochrome c or Candida antarctica lipase B (CALB). However, the inclusion of phenolic compounds (phenol or caffeic acid) to reaction mixtures of these proteins can greatly enhance the levels of cross-linking. For example it is possible to prepare cross-linked aggregates of industrially applicable enzymes such as CALB by simply incubating it with Vs-tyrosinase and phenol. The resulting aggregates can be collected by centrifugation and retain high levels of activity and may find applications in biocatalysis.
 ...
PMID:Cross-linking and immobilisation of different proteins with recombinant Verrucomicrobium spinosum tyrosinase. 2096 99


1 2 Next >>