Properties of polyphenol oxidase from tubers of the yam Dioscorea bulbifera

The subunit MW of Dioscorea bulbifera polyphenol oxidase (MW 115 000 ± 2000) determined by SDS-PAGE is ca. 31 000 indicating that the enzyme is an oligomeric protein with four subunits. K_i values of various inhibitors and their modes of inhibition have been determined with catechol and pyrogallol as substrates. p-Nitrophenol, p-cresol, quinoline and resorcinol are competitive inhibitors of catechol binding while only orcinol and p-nitrophenol behave in the same way towards pyrogallol as substrate. From the effect of pH on V_max, groups with pK values ca. 4.7 and 6.8 have been identified to be involved in catalytic activity. The Arrhenius activation energy (E_a) at pH 4.0 is 8.9 kcal/mol between 40–65°. At pH 7.0, the value is 22.1 kcal/mol between 40 and 60°. The enthalpies (ΔH) at pH 4.0 and pH 7.0 are 2.3 kcal/mol and 32.4 kcal/mol respectively. The results are discussed considering the conformational changes of the enzyme during substrate binding.     

Polyphenol oxidase activity in dormant saffron (<Emphasis Type="Italic">Crocus sativus</Emphasis> L<Emphasis Type="Italic">.</Emphasis>) corm

Crocus sativus L., cultivated since ancient times as the source of saffron, is a triploid plant that can be propagated only via its corms which undergo a period of dormancy. Understanding the processes taking place in the corm is essential to preserve the plant and improve its quality. Color and taste being of prime importance in the quality of the saffron spice, knowledge on polyphenol oxidase (PPO) activity in the plant is of particular interest given the role of the enzyme in fruit and vegetable browning during processing and during the storage of processed food. In this paper, PPO activity was investigated for the first time in extracts obtained from dormant C. sativus L. corms. PPO activity was detectable using l-DOPA, pyrogallol, catechol or p-cresol as substrate, each being oxidized to its corresponding o-quinone; no activity was detectable with l-tyrosine, tyramine or phenol as substrate. Two pH optima, respectively at 4.5 and 6.7, were observed with all substrates and a third one, at 8.5, was found with l-DOPA and p-cresol. Kinetics parameters studied at pH 6.7 indicated the highest catalytic efficiency (in units mg⁻¹ prot mM⁻¹) with pyrogallol: 150, then catechol: 39, l-DOPA: 6.4 and p-cresol: 4.6. The enzymatic activity was inhibited by 50% in the presence of 0.22, 0.35, 0.5 and 0.7 mM kojic acid with, respectively, catechol, pyrogallol, p-cresol and l-DOPA as substrate. When stained for PPO activity, non-denaturing gel electropherograms of extract revealed three distinct bands, indicating the presence of multiple isoenzymes in dormant C. sativus L. corms.     

Studies on the destruction of indole-3-acetic acid by a species of Arthrobacter IV. Decomposition products

Products of IAA decomposition by IAA destroying enzyme-inducedand non-induced cells of Arthrobacter sp. were examined. Catecholand pyrogallol, and 3-methyldioxindole were respectively identifiedfor non-induced and induced cells. Exogenous catechol was readilyoxidized by induced cells, but was not oxidized by non-inducedcells. Exogenous pyrogallol, 3-methyldioxindole, indole-3-aldehyde,skatole, 2,3-dihydroxindole, 3-methyleneoxindole, o-aminoacetophenone,3-hydroxyanthranilic acid, anthranilic acid and salicylic acidwere oxidized by neither induced nor non-induced cells. (Received June 16, 1969; )     

Oxidation of phenols by cells and cell-free enzymes from Candida tropicalis

A yeast strain isolated from soil by enrichment on phenol as major carbon source was identified as Candida tropicalis. Washed cell suspensions of this strain and cell-free preparations obtained from mechanically disrupted cells oxidized phenol via catechol and cis, cis-muconate. In addition to phenol and the three isomeric diphenols, a number of phenol derivatives, amongst them fluoro-, nitro- and short-chain alkyl-phenols, were oxidized by the organism. However, no significant oxygen uptake could be demonstrated in the presence of pyrogallol, phloroglucinol, the cresols, the m-and p-hydroxy-benzoates, methoxylated phenol derivatives, benzene or toluene. Cell-free preparations from the yeast strain exhibited activity of phenol hydroxylase and of catechol 1,2-oxygenase. Both enzymes appeared in the soluble cell fraction. Both exhibit broad substrate specificities. The relative specific activity of the ring-cleaving enzyme towards various substrates seems to be dependent on the phenolic inducer.     

Some kinetic properties of polyphenol oxidase from Thymbra spicata L. var. spicata

Polyphenol oxidase (PPO) of Thymbra (Thymbra spicata L. var. spicata) was isolated by (NH₄)₂SO₄ precipitation and dialysis. A diphenolase from Thymbra plant, active against 4-methylcatechol, catechol and pyrogallol was characterized in detail in terms of pH and temperature optima, stability, kinetic parameters and inhibition behaviour towards some general PPO inhibitors. 4-Methylcatechol was the most suitable substrate, due to the lowest K_m and the biggest V_max/K_m values, followed by catechol and pyrogallol. The Thymbra PPO had maximum activity at pH 5.0, 7.0 and 8.0 with 4-methylcatechol, catechol and pyrogallol substrates, respectively. The optimum temperature of activity for Thymbra PPO was 30, 40 and 50 °C for 4-methylcatechol, catechol and pyrogallol substrates, respectively. It was found that optimum temperature and pH were substrate-dependent studied. The enzyme activity decreased due to heat denaturation of the enzyme with increasing temperature and inactivation time. Inhibition of Thymbra PPO was investigated with inhibitors such as l-cysteine and glutathione using 4-methylcatechol, catechol and pyrogallol as substrates. It was found that l-cysteine was a more effective inhibitor than glutathione owing to lower K_i. The type of inhibition depended on the origin of the PPO studied and also on the substrate used. Furthermore, the IC₅₀ values of inhibitors sudied on PPO were determined by means of activity percentage (I) diagrams.     

槐尺蠖多酚氧化酶的纯化及酶学特征

经40%饱和度硫酸铵分级沉淀,Sephadex G-100凝胶过滤等步骤,将槐尺蠖Semiothisa cinerearia Bremer et Grey 多酚氧化酶纯化,纯化倍数为6.96倍。该酶对焦性没食子酸,邻苯二酚和L多巴的Km值分别为0.23 mmol/L, 0.48 mmol/L和0.49 mmol/L。多酚氧化酶在pH 7.0,37℃时活性最高,并在40℃以上条件下,随着保温时间的延长酶活力下降。用槲皮苷和硫脲作抑制剂对该酶活性的抑制结果表明,这两种抑制剂分别属于竞争性和非竞争性抑制剂。     

Extradiol Cleavage of 3-Methylcatechol by Catechol 1,2-Dioxygenase from Various Microorganisms

The isofunctional enzymes of catechol 1,2-dioxygenase from species of Acinetobacter, Pseudomonas, Nocardia, Alcaligenes, and Corynebacterium oxidize 3-methylcatechol according to both the intradiol and extradiol cleavage patterns. However, the enzyme preparations from Brevibacterium and Arthrobacter have only the intradiol cleavage activity. Comparison of substrate specificity among these isofunctional dioxygenases shows striking differences in the oxidation of 3-methylcatechol, 4-methylcatechol and pyrogallol.     

o-Diphenol: Oxygen oxidoreductase from leaves of sugar cane

A non-particulate o-diphenol: O₂ oxidoreductase (phenolase) has been isolated from leaves of sugar cane. Gel filtration produced two fractions MW 32000 and 130000. The preferred substrate was chlorogenic acid. Other o-diphenols (caffeic acid, catechol, pyrogallol, dihydroxyphenylalanine) all of which were slowly oxidized when tested alone, increased the rates of O₂ consumption obtained with catalytic amounts of chlorogenic acid. Both enzyme fractions were inhibited by thiols; thioglycollate, which acted in a non-competitive manner, was most effective.     

Properties of acid phosphatase in the cell wall of tobacco cells cultured in vitro

A cell-wall fraction containing 10.0% dry weight of proteinwas isolated from tobacco (Nicotiana tabacum L.) XD-6 cellscultured in suspension. The fraction possessed high acid phosphataseactivity toward p-nitrophenyl phosphate, phenyl phosphate, inorganicpyrophosphate, adenosine diphosphate, nucleoside triphosphates,and bis- (p-nitrophenyl) phosphate; much less activity towardnaphthyl phosphate, ß-glycerophosphate, glucose-6-phosphate,fructose-6-phosphate, fructose-l,6-diphosphate, thiamine pyrophosphate;and no activity toward glucose-1-phosphate and inositol hexaphosphate.Metallic ions were not required for activation. The enzyme wasextracted from the wall with NaCl solution. The solubilizedenzyme resulted in a single peak on Sephadex G-150 chromatographywith activity toward p-nitrophenyl phosphate, pyrophosphate,and bis(p-nitrophenyl) phosphate. The activity of the solubilizedenzyme toward p-nitrophenyl phosphate was identical with thebound enzyme in its pH optimum, substrate specificity, ion inhibitionand Km value, but it was more sensitive to pH, substrate difference,inhibition, and heat treatment. ¹Present address: Department of Biology, Japan Women's University,Mejiro-dai, Bunkyo-ku, Tokyo, Japan (Received September 13, 1972; )     

Purification and partial biochemical characterization of polyphenol oxidase from mamey (Pouteria sapota)

While a long shelf life for fruit products is highly desired, enzymatic browning is the main cause of quality loss in fruits and is therefore a main problem for the food industry. In this study polyphenol oxidase (PPO), the main enzyme responsible for browning was isolated from mamey fruit (Pouteria sapota) and characterized biochemically. Two isoenzymes (PPO 1 and PPO 2) were obtained upon ammonium sulfate precipitation and hydrophobic and ion exchange chromatography; PPO 1 was purified up to 6.6-fold with 0.28% yield, while PPO 2 could not be characterized as enzyme activity was completely lost after 24 h of storage. PPO 1 molecular weight was estimated to be 16.1 and 18 kDa by gel filtration and SDS-PAGE, respectively, indicating that the native state of the PPO 1 is a monomer. The optimum pH for PPO 1 activity was 7. The PPO 1 was determined to be maximum thermally stable up to 35 °C. Kinetic constants for PPO 1 were K_m = 44 mM and K_m = 1.3 mM using catechol and pyrogallol as substrate, respectively. The best substrates for PPO 1 were pyrogallol, 4-methylcatechol and catechol, while ascorbic acid and sodium metabisulfite were the most effective inhibitors.     

Purification and characterization of peroxidase from cauliflower (Brassica oleracea L. var. botrytis) buds

Peroxidases (EC 1.11.1.7; donor: hydrogen peroxide oxidoreductase) are part of a large group of enzymes. In this study, peroxidase, a primer antioxidant enzyme, was purified with 19.3 fold and 0.2% efficiency from cauliflower (Brassica oleracea L.) by ammonium sulphate precipitation, dialysis, CM-Sephadex ion-exchange chromatography and Sephadex G-25 purification steps. The substrate specificity of peroxidase was investigated using 2,2'-azino-bis(3-ethylbenz-thiazoline-6-sulphonic acid) (ABTS), 2-methoxyphenol (guaiacol), 1,2-dihydroxybenzene (catechol), 1,2,3-trihyidroxybenzene (pyrogallol) and 4-methylcatechol. Also, optimum pH, optimum temperature, optimum ionic strength, stable pH, stable temperature, thermal inactivation conditions were determined for guaiacol/H(2)O(2), pyrogallol/H(2)O(2), ABTS/H(2)O(2), catechol/H(2)O(2) and 4-methyl catechol/H(2)O(2) substrate patterns. The molecular weight (M(w)) of this enzyme was found to be 44 kDa by gel filtration chromatography method. Native polyacrylamide gel electrophoresis (PAGE) was performed for isoenzyme determination and a single band was observed. K(m) and V(max) values were calculated from Lineweaver-Burk graph for each substrate patterns.     

Biosensor for the determination of phenols based on cross-linked enzyme crystals (CLEC) of laccase

Cross-linked enzyme crystals (CLECs) are a versatile form of biocatalyst that can also be used for biosensor application. Laccase from Trametes versicolor (E.C.1.10.3.2) was crystallized, cross-linked and lyophilized with beta-cyclodextrin. The CLEC laccase was found to be highly active towards phenols like 2-amino phenol, guaiacol, catechol, pyrogallol, catechin and ABTS (non-phenolic). The CLEC laccase was embedded in 30% polyvinylpropylidone (PVP) gel and mounted into an electrode to make the sensor. The biosensor was used to detect the phenols in 50-1000 micromol concentration level. Phenols with lower molecular weight such as 2-amino phenol, catechol and pyrogallol gave a short response time where as the higher molecular weight substrates like catechin and ABTS had comparatively a long response time. The optimum pH of the analyte was 5.5-6.0 when catechol was used as substrate. The CLEC laccase retained good activity for over 3 months.     

Isolation and characterization of catechol oxidase from Solanum melongena

Catechol oxidase was distributed in soluble and particulate fractions of Solanum melongena. The purified preparation appears to be homogeneous by polyacrylamide gel electrophoresis. The enzyme shows two pH maxima—with catechol, 6.5 and 7.5; and with dopa, 6.5 and 7.9. The latent form of the enzyme does not occur in S. melongena. The preparation resembles the enzyme from other sources in substrate specificity towards various mono- and diphenols, having a higher affinity for catechol than dopa; this tendency increases on purification. The cresolase activity decreases with purification and a lag period with p-cresol is observed. The oxidation of mono- and diphenols is inhibited by ascorbic acid, sulphydryl compounds and chelating agents.     

Formation of Catechol Oxidase in Seed Coats of Pisum elatius during Seed Maturation

The catechol oxidase present in the seed coat of Pisum elatiusat various stages of seed maturation was partially characterized.The pH dependence and response to inhibitors and stimulatorsof the enzyme was determined. Inhibitors of protein synthesisand enzyme activity were introduced into the developing seedsvia the pod. During the early stages of seed maturation, theincreased enzyme activity was probably due to de novo synthesiswhile the increase in the later stages of maturation can bestbe accounted for on the basis of activation of pre-existingenzyme, perhaps due to conformational changes in the enzyme.The evidence for this view is discussed.     

Some Characteristics and Inhibitors of Indoleacetic Acid Oxidase from Tissue 2

Extracts from tissue cultures of crown-gall from Parthenocissuscatalysed the destruction of indoleacetic acid in vitro withoptimum activity at pH 4·5. The presence of two co-factors,Mn⁺⁺ and 2,4-dichlorophenol, was necessary for this activity,which was found to be strictly aerobic. Chlorogenic acid, caffeic acid, scopoletin, ferulic acid, andgibberellic acid markedly inhibited IAA-destruction. Chlorogenicacid inhibition was reversed by the addition of H₂O₂. Chlorogenicacid was not oxidized by the IAA-destroying system and did notbehave as a competitive inhibitor. The IAA-oxidase extract manifested peroxidase and phenolaseactivity with catechol and pyrogallol as substrates. However,this activity was greater at pH 7·0 than at the optimumfor IAA-oxidase activity, pH 4·5. Further evidence ofthe existence of these two enzymes in the intact tissue wasdemonstrated by histochemical studies. In tissue slices, peroxidaseactivity was very high and widely distributed while phenolaseactivity was low and restricted to localized centres of thetissue.     

Unprecedented access of phenolic substrates to the heme active site of a catalase: Substrate binding and peroxidase‐like reactivity of Bacillus pumilus catalase monitored by X‐ray crystallography and EPR spectroscopy

Heme‐containing catalases and catalase‐peroxidases catalyze the dismutation of hydrogen peroxide as their predominant catalytic activity, but in addition, individual enzymes support low levels of peroxidase and oxidase activities, produce superoxide, and activate isoniazid as an antitubercular drug. The recent report of a heme enzyme with catalase, peroxidase and penicillin oxidase activities in Bacillus pumilus and its categorization as an unusual catalase‐peroxidase led us to investigate the enzyme for comparison with other catalase‐peroxidases, catalases, and peroxidases. Characterization revealed a typical homotetrameric catalase with one pentacoordinated heme b per subunit (Tyr340 being the axial ligand), albeit in two orientations, and a very fast catalatic turnover rate (k_cat = 339,000 s^?1). In addition, the enzyme supported a much slower (k_cat = 20 s^?1) peroxidatic activity utilizing substrates as diverse as ABTS and polyphenols, but no oxidase activity. Two binding sites, one in the main access channel and the other on the protein surface, accommodating pyrogallol, catechol, resorcinol, guaiacol, hydroquinone, and 2‐chlorophenol were identified in crystal structures at 1.65–1.95 Å. A third site, in the heme distal side, accommodating only pyrogallol and catechol, interacting with the heme iron and the catalytic His and Arg residues, was also identified. This site was confirmed in solution by EPR spectroscopy characterization, which also showed that the phenolic oxygen was not directly coordinated to the heme iron (no low‐spin conversion of the Fe^III high‐spin EPR signal upon substrate binding). This is the first demonstration of phenolic substrates directly accessing the heme distal side of a catalase. Proteins 2015; 83:853–866. © 2015 Wiley Periodicals, Inc.     

Coloured and low conductive fabrics by in situ laccase-catalysed polymerization

Coloured and conductive fabrics were obtained through “in situ” laccase polymerization of catechol and p-phenylenediamine under high-pressure homogenization. Both monomers, catechol and p-phenylenediamine, were polymerized by different laccase forms, namely native, PEGylated and Epoxy-PEGylated. All the catalysts were placed inside a textile fabric bag which served simultaneously as enzyme support and as substrate for coating with the newly produced polymers. The PEGylated laccase forms gave rise to a higher amount of oligomers/polymers and higher colouration level of polyethylene terephthalate (PET), cotton and wool fabrics compared to native laccase. Both functional polymers were able to confer conductivity to the substrates however in a different extent. Fabrics coated with poly(p-phenylenediamine) present higher conductivity, rather due to its polymerized structure than to the amount of polymer produced by enzyme catalysis. Herein a green approach was presented to produce polyphenols with increased fixation onto different textile substrates. These substrates reach high levels of colouration and good fastness behaviour after washing.     

Purification of lactoperoxidase from bovine milk and investigation of the kinetic properties.

Lactoperoxidase (LPO) was purified from bovine milk using Amberlite CG 50 H+ resin, CM Sephadex C-50 ion-exchange chromatography, and Sephadex G-100 gel filtration chromatography. During the purification steps, the activity of enzyme was measured using 2,2'-azino-bis (3-ethylbenzthiazoline-6 sulfonic acid) diamonium salt (ABTS) as a chromogenic substrate at pH 6. Optimum pH and optimum temperature values for LPO were determined for ABTS, p-phenylendiamine, catechol, epinephrine, and pyrogallol as substrates, and then Km and Vmax values for the same substrate were obtained by means of Lineweaver-Burk graphics. The purification degree of the enzyme was controlled by SDS-PAGE and Rz (A412/A280) values. Km values, at optimum pH and 20 degrees C, were 0.197 mM, 0.063 mM, 0.64 mM, 25.2 mM, and 63.95 mM for p-phenylendiamine, ABTS, epinephrine, pyrogallol, and catechol, respectively. Vmax values, at optimum pH and 20 degrees C, were 3.5x10(-5) EU/mL, 4.0x10(-5) EU/mL, 5.8x10(-4) EU/mL, 8.4x10(-4) EU/mL, and 1.01x10(-3) EU/mL for the same substrates, respectively. p-Phenylendiamine was first found as a new substrate for LPO.     

Phenolic compounds inhibit the aldose reductase enzyme from the sheep kidney

Aldose reductase (AR) is the key enzyme for the polyol pathway and responsible for sorbitol accumulation during the hyperglycemia. The present article focuses on the role of phenol, pyrogallol, hydroquinone, resorcinol, catechol, and phloroglucinol in in vitro inhibition of AR. For this purpose, AR was purified from the sheep kidney with 5.33 EU mg^?1 specific activity and 0.64% yield using several chromatographic methods. Various concentrations of the compounds were tested on in vitro AR activity. IC₅₀ values were found for phenol, pyrogallol, hydroquinone, resorcinol, catechol, and phloroglucinol as 6.5, 1.13, 5.45, 2.21, 1.8, and 2.09 mM, respectively, and their K_i constant was calculated as 3.45 ± 0.92, 0.96 ± 0.28, 3.07 ± 0.46, 1.59 ± 0.43, 2.5 ± 0.35, and 2.54 ± 0.45 mM, respectively. Pyrogallol showed better inhibitory effect compared to the other compounds. The inhibition mechanisms of all compounds were noncompetitive. In the presents study, in vitro AR inhibition was examined by the phenolic compounds.     

A Novel Catechol Oxidase Enzyme Electrode for the Specific Determination of Catechol

An enzyme electrode for the specific determination of catechol was developed by using catechol oxidase (EC 1.10.3.1) from eggplant (Solanum melangena L.) in combination with a dissolved oxygen probe. Optimization studies of the prepared catechol oxidase enzyme electrode established a phosphate buffer 50 mM at pH 7.0 and 35°C to provide the optimum conditions for affirmative electrode response. The enzyme electrode response depended linearly on a catechol concentration range of 5?10^-7-30?10^-5 M with a response time of 25 sec and substrate specificity of the catechol oxidase electrode of 100%. The biosensor retained its enzyme activity for at least 70 days.