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)

A partial characterization of peroxidase (POD) and polyphenol oxidase (PPO) activities in blackberry fruits is described. Two cultivars of blackberry (Wild and Thornless) were analyzed for POD and PPO activities. Stable and highly active POD and PPO extracts were obtained using insoluble poly(vinylpyrrolidone) and Triton X-100 in 0.05 M sodium phosphate, pH 7.5, buffer. Blackberry POD and PPO activities have a pH optimum of 6.5, in a reaction mixture of 0.2 M sodium phosphate. Optimal POD activity was found with 3% o-dianisidine. Maximum PPO activity was found with catechol (catecholase activity) followed by 4-methylcatechol. Polyacrylamide gel electrophoresis of blackberry extracts under non-denaturing conditions resolved in various bands. In the POD extracts of Wild fruits, there was only one band with a mobility of 0.12. In the Thornless POD extracts there were three well-resolved bands, with R(f) values of 0.63, 0.36, and 0.09. Both the Wild and Thornless blackberry cultivars produced a single band of PPO, with R(f) values of 0.1 for Wild and 0.06 for Thornless.
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PMID:Partial characterization of peroxidase and polyphenol oxidase activities in blackberry fruits. 1108 2

In the present paper, a fully latent polyphenol oxidase (PPO) from desert truffle (Terfezia claveryi Chatin) ascocarps is described for the first time. The enzyme was partially purified by using phase partitioning in Triton X-114 (TX-114). The achieved purification was 2-fold from a crude extract, with a 66% recovery of activity. The interfering lipids were reduced to 13% of the original content. In addition, the purification gave rise to a reduction of phenolic compounds to only 37.5%, thus avoiding the postpurification tanning of the enzyme. Latent PPO was activated by the anionic surfactant sodium dodecyl sulfate (SDS) or by incubation with trypsin. The amount of SDS necessary to obtain a maximum activation was dependent on the nature of the substrate. The use of SDS also permitted the histochemical localization of the latent enzyme within the ascocarp. Terfezia polyphenol oxidase was kinetically characterized using two phenolic substrates (L-DOPA and tert-butylcatechol). The latter substrate presented inhibition at high substrate concentration with a K(si) of 6.3 mM. Different inhibiting agents (kojic and cinnamic acid, mimosine and tropolone) were also studied, tropolone being the most effective.
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PMID:Partial purification, characterization, and histochemical localization of fully latent desert truffle (Terfezia claveryi Chatin) polyphenol oxidase. 1130 47

Polyphenol oxidase (EC 1.10.3.1, o-diphenol: oxygen oxidoreductase, PPO) of banana (Musa sapientum L.) peel was partially purified about 460-fold with a recovery of 2.2% using dopamine as substrate. The enzyme showed a single peak on Toyopearl HW55-S chromatography. However, two bands were detected by staining with Coomassie brilliant blue on PAGE: one was very clear, and the other was faint. Molecular weight for purified PPO was estimated to be about 41 000 by gel filtration. The enzyme quickly oxidized dopamine, and its Km value (Michaelis constant) for dopamine was 3.9 mM. Optimum pH was 6.5 and the PPO activity was quite stable in the range of pH 5-11 for 48 h. The enzyme had an optimum temperature at 30 degrees C and was stable up to 60 degrees C after heat treatment for 30 min. The enzyme activity was strongly inhibited by sodium diethyldithiocarbamate, potassium cyanide, L-ascorbic acid, and cysteine at 1 mM. Under a low buffer capacity, the enzyme was also strongly inhibited by citric acid and acetic acid at 10 mM.
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PMID:Partial purification and characterization of polyphenol oxidase from banana (Musa sapientum L.) peel. 1131 78

The activity of potato polyphenol oxidase (tyrosinase) toward DL-3,4-dihydroxyphenylalanine (K(M) 5.39 mM) was studied using a variety of carboxylate buffers at a common pH and ionic strength. Enzyme activity, greatest in citrate and least in oxalate, correlated with increasing carboxyl concentration and molecular mass. The lower activity in oxalate was attributed to more effective chelation of a copper(II) form of the enzyme by the oxalate dianion. Sodium halide salts inhibited the enzyme. Although there was little difference in inhibition between sodium and potassium salts, the degree and type of inhibition was anion dependent; K(is), values for NaCl and KCl, (competitive inhibitors) were 1.82 and 1.62 mM, whereas Na(2) SO(4) and K(2) SO(4) (mixed inhibitors) had K(is) and K(ii) values in the 250 to 450 mM range.
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PMID:Inhibition of potato polyphenol oxidase by anions and activity in various carboxylate buffers (pH 4.8) at constant ionic strength. 1134 82

The melanosome is a unique secretory granule of the melanocyte in which melanin pigments are synthesized by tyrosinase gene family glycoproteins. Melanogenesis is a highly regulated process because of its inherent toxicity. An understanding of the various regulatory mechanisms is important in delineating the pathophysiology involved in pigmentary disorders and melanoma. We have purified and analyzed the total melanosomal proteins from B16 mouse melanoma tumors in order to identify new proteins that may be involved in the control of the melanogenesis process. Melanosomal proteins were resolved by two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis, a predominant spot (27 kDa with isoelectric point 5.8-6.4) was excised and digested with cyanogen bromide, and the fragments were sequenced. Synthetic oligonucleotide primers were synthesized corresponding to the peptide sequences, and reverse transcriptase polymerase chain reaction amplification of total RNA from B16 cells was carried out. Sequencing of one of the polymerase-chain-reaction-mediated clones demonstrated 80%-97% sequence homology of 200 bp nucleotide with GTP-binding proteins at the 3'-untranslated region. GTP-binding assay on two-dimensional gels of melanosomal proteins showed the presence of several (five to six) small GTP-binding proteins, suggesting that small GTP-binding proteins are associated with the melanosome. Among the known GTP-binding proteins with similar molecular weight and isoelectric point ranges, rab3, rab7, and rab8 were found to be present in the melanosomal fraction by immunoblotting. Confocal immunofluorescence microscopy showed that rab7 is colocalized with the tyrosinase-related protein 1 around the perinuclear area as well as, in part, in the perikaryon, thereby suggesting that rab7 might be involved in the intracellular transport of tyrosinase-related protein 1. Tyrosinase-related protein 1 transport was blocked by the treatment of B16 cells with antisense oligonucleotide to rab7. We suggest (i) that rab7 is a melanosome-associated molecule, (ii) that tyrosinase-related protein 1 is present in late-endosome delineated granules, and (iii) that rab7 is involved in the transport of tyrosinase-related protein 1 from the late-endosome delineated granule to the melanosome.
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PMID:Identification of rab7 as a melanosome-associated protein involved in the intracellular transport of tyrosinase-related protein 1. 1144 53

A kinetic study of the diphenolase activity of latent polyphenol oxidase (PPO), purified from Iceberg lettuce (Lactuca sativa L), revealed a sigmoid relationship between the reaction rate and the substrate concentration with a high Hill coefficient (n(H) = 3.8). This positive cooperativity had not been previously described for any PPO. Furthermore, the enzyme showed a lag phase in the expression of this activity, suggesting a hysteretic nature of the enzyme. The kinetic behavior, the latency and the lag phase varied at different steps of the purification process. PPO showed hyperbolic or cooperative kinetics depending on the pH assay and the sodium dodecyl sulfate (SDS) concentration. Substrate-induced slow conformational change of the oligomeric enzyme is suggested. The conformational change would be toward a more active enzyme form with higher affinity for the substrate and favoured by acid pH and SDS.
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PMID:Hysteresis and positive cooperativity of iceberg lettuce polyphenol oxidase. 1172 15

Laccase-like activity was detected in melanin-producing strains of Sinorhizobium meliloti mainly in cells at the stationary growth phase when copper was added to the medium. The laccase showed both syringaldazine and ABTS (2,2'-azino-bis-ethylbenzthiazoline-6-sulfonic acid) oxidase activities and was activated by the addition of 1.7 mM sodium dodecyl sulfate. Activity was totally inhibited by the addition of 1.0 mM EDTA, suggesting that the enzyme is a metal-dependent one. The enzyme was found to be cytosolic having an optimum pH of 5.0, an estimated molecular mass of 95 kDa and a K(m) of 4 microM for syringaldazine. Both laccase and tyrosinase activities were detected in melanin-producing S. meliloti strains. Plant growth-promoting (PGP) effect in rice by a laccase-producing S. meliloti strain when co-inoculated with Azospirillum brasilense Cd was observed. PGP effect by co-inoculation significantly increased plant yield compared to A. brasilense by itself. To the best of our knowledge this is the first report on laccase production in rhizobia and cooperation between Azospirillum and Sinorhizobium in rice.
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PMID:Laccase activity in melanin-producing strains of Sinorhizobium meliloti. 1200 64

The interaction between two proteins, Mefp-1 and Mefp-2, from the byssal plaque of the blue mussel, Mytilus edulis, was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D) technique. The challenge in using a surface-sensitive technique to investigate the interaction between two strongly adhesive proteins was met by coupling a biotinylated version of one of the proteins (b-Mefp-1) to an inert two-dimensional arrangement of streptavidin (SA) formed on top of a biotin-doped supported phospholipid bilayer. The interaction between Mefp-1 and Mefp-2 was further investigated by addition of Mefp-2 to SA-coupled b-Mefp-1, where the latter was either in the native state or cross-linked using sodium periodate (NaIO(4)), Cu(2+), or mushroom tyrosinase. With this coupling strategy it is shown that a requirement for attraction between the two proteins is that tyrosinase is used as the cross-linking agent of b-Mefp-1. By inhibiting the enzymatic activity of tyrosinase it is also shown that enzymatic activity is required for both efficient binding of tyrosinase to SA-coupled b-Mefp-1 as well as for the subsequent binding of Mefp-2. In contrast, spontaneous adsorption of Mefp-1 to a methyl-terminated (thiolated) gold surface followed by addition of Mefp-2 results in binding of Mefp-2 for all cross-linking agents. This suggests that cross-linking of Mefp-1 adsorbed on a solid surface induces structural changes in the adsorbed protein layer, resulting in exposure of free surface patches on which Mefp-2 binds.
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PMID:The influence of cross-linking on protein-protein interactions in a marine adhesive: the case of two byssus plaque proteins from the blue mussel. 1209 17

Using L-DOPA as a probe, phenoloxidase (PO) from Penaeus chinensis hemolymph was purified by gel-filtration and ion-exchange chromatography, and characterized in terms of its molecular weight and enzymatic properties in this study. It was found that prophenoloxidase (proPO) isolated as monomeric protein had a molecular weight of 87.5 kD, and a 77 kD phenoloxidase molecule was often contained in preparations. The 87.5 kD proPO had a very low enzymatic activity on 0.02 mmol/L L-DOPA, whereas the 77 kD PO had a very high enzymatic activity on L-DOPA. Enzymatic activity of PO against L-DOPA was optimal at pH 6.0, temperature of 40 degrees, and with an apparent K(m) value of 1.99 mmol/L. The PO activity was extremely sensitive to ascorbic acid, cysteine and dithiothreitol, very sensitive to thio urea, however not sensitive to sodium sulfite, citric acid and benzoic acid, confirmed that it was a phenoloxidase, combined with its specific oxidase activity on substrate of monophenol and L-DOPA, indicate that it was a tyrosinase type phenoloxidase. This enzyme is very sensitive to EDTA and metal ions, its activity is strongly enhanced by Mg(2+) and strongly inhibited by Cu(2+), which indicates that this PO is probably a kind of metalloenzyme.
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PMID:[Purification and partial biochemical characterization of phenoloxidase from Penaeus chinensis]. 1219 61

3,4-Dihydroxyphenylalanine (DOPA) residues are known for their ability to impart adhesive and curing properties to mussel adhesive proteins. In this paper, we report the preparation of linear and branched DOPA-modified poly(ethylene glycol)s (PEG-DOPAs) containing one to four DOPA endgroups. Gel permeation chromatography-multiple-angle laser light scattering analysis of methoxy-PEG-DOPA in the presence of oxidizing reagents (sodium periodate, horseradish peroxidase, and mushroom tyrosinase) revealed the formation of oligomers of methoxy-PEG-DOPA, presumably resulting from oxidative polymerization of DOPA endgroups. In the case of PEG-DOPAs containing two or more DOPA endgroups, oxidative polymerization resulted in polymer network formation and rapid gelation. The amount of time required for gelation of aqueous PEG-DOPA solutions was found to be as little as 1 min and was dependent on the polymer architecture as well as the type and concentration of oxidizing reagent used. Analysis of reaction mixtures by UV-vis spectroscopy allowed the identification of reaction intermediates and the elucidation of reaction pathways. On the basis of the observed reaction intermediates, oxidation of the catechol side chain of DOPA resulted in the formation of highly reactive DOPA-quinone, which further reacted to form cross-linked products via one of several pathways, depending on the presence or absence of N-terminal protecting groups on the PEG-DOPA. N-Boc protected PEG-DOPA cross-linked via phenol coupling and quinone methide tanning pathways, whereas PEG-DOPA containing a free amino group cross-linked via a pathway that resembled melanogenesis. Similar differences were observed for the rate of gel formation as well as the molecular weight between cross-links ((-)M(c)), calculated using equilibrium swelling and the Flory-Rehner equation.
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PMID:Synthesis and gelation of DOPA-modified poly(ethylene glycol) hydrogels. 1221 51


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