A wounding-induced PPO from cowpea (Vigna unguiculata) seedlings

Extraction of ingredients from tea leaves using oxidative enzymatic reaction and optimization of extraction conditions

Peroxidase (POD) and polyphenol oxidase (PPO) are used as biocatalyst in many processes such as oxidization reactions, wastewater treatment, phenol synthesis and so on. The purpose of current study is enzymes extraction from biomass (tea leaves) as well as evaluation of their activation. Different parameters including temperature, buffer concentration, buffer type, buffer/tea leaves ratio, addition of high molecular weight polymers and emulsifiers, and pH were optimized in order to obtain the highest enzymes activity. Response Surface Methodology (RSM) procedure is employed for statistical analysis of enzymes extraction. It is understood from the result that PPO and POD possess the highest activity at temperatures of 25 °C and 50 °C, pH 7 and 5, buffer molarity of 0.1, and 0.05, buffer/tea leaves ratio = 5 for both, contact time = 20 min and 10 min, and presence of 6% and 3% PVP, 5% and 0% Tween 80 for PPO and POD, respectively. Amounts of highest activity for PPO and POD biocatalysts were calculated 0.42 U/mL and 0.025493 U/mL, respectively. Moreover, the entire inactivation of PPO took place after 30 min at 40 °C and 60 °C and 20 min at 80 °C. However, POD lost 35% of its activity after 30 min at 40 °C and 60 °C. The amount of 6% POD activity was kept after 45 min at 80 °C. Generally, it was indicated that POD was more resistant to thermal treatment than PPO.

Partial purification and characterization of the quality deteriorating enzymes from Indian pink guava (Psidium guajava L.), var. Lalit

Peroxidase (POD), polyphenol oxidase (PPO), ascorbate oxidase (AO) and pectin methylesterase (PME) from 'Lalit' guava variety have been purified using BioGel P-100 and UNOsphere Q resins. POD, PPO, AO, and PME were partially purified to 28, 30, 36 and 30 fold; single band on SDS-PAGE represented a molecular weight of 21, 70, 75, 50 kDa, respectively. Optimum pH for POD and AO was 6.5 whereas, PPO and PME showed optimum pH in the alkaline range of pH 8.0 and 8.5, respectively. AO showed optimum activity at 25 °C, POD and PPO showed optimum activity at 35 °C; however, PME showed maximum activity at 55 °C. AO was the most heat labile whereas, PME was the most heat stable enzyme studied and may carry an important role in the thermal processing of guava pulp as an indicator of the efficacy of treatment.

Foliar Desiccators Glyphosate, Carfentrazone, and Paraquat Affect the Technological and Chemical Properties of Cowpea Grains

The effects of the use of glyphosate (GLY), glyphosate plus carfentrazone (GLY/CAR), and paraquat (PAR) as plant desiccators on the technological and chemical properties of cowpea grains were investigated. All studied desiccants provided lower cooking time to freshly harvested cowpea. However, the coat color of PAR- and GLY/CAR-treated cowpea was reddish in comparison to the control treatment. Principal component analysis (PCA) from liquid chromatography-mass spectrometry (LC-MS) data sets showed a clear distinction among cowpea from the different treatments. Catechin-3-glucoside and epicatechin significantly contributed for discriminating GLY-treated cowpea, while citric acid was responsible for discriminating GLY/CAR-treated cowpea. Quercetin derivative and gluconic acid were responsible for discriminating control treatment. Residual glyphosate and paraquat content was higher than the maximum limits allowed by Codex Alimentarius and the European Union Commission. Improvements in the technological and chemical properties of cowpea may not be overlapped by the risks that those desiccants exhibit when exceeding the maximum limits of tolerance in food.

Characterization of Active Anthocyanin Degradation in the Petals of Rosa chinensis and Brunfelsia calycina Reveals the Effect of Gallated Catechins on Pigment Maintenance

Anthocyanin degradation decreases ornamental or nutritional values of horticultural products. To investigate factors that may influence colour change in flower development, anthocyanin degradation was compared between the flowers of Brunfelsia calycina and Rosa chinensis, which show rapid and slow degradation, respectively. In-gel activity assays, high performance liquid chromatography (HPLC) analysis of tannins, enzyme kinetics measurement and immune-detection of anthocyanin degradation related-perioxidases (PODs) were carried out for the comparison. Rose petals possessed significantly lower anthocyanin degradation-related POD activities than Brunfelsia petals, which may be related to the high tannin contents. Epicatechin gallate (ECG) and gallocatechin gallate (GCG) were detected in rose as 161.3 ± 12.34 and 273.56 ± 41.23 μg/g FW (Fresh Weight) respectively, while not detected in Brunfelsia. ECG and GCG inhibited the activities of the Brunfelsia POD with half maximal inhibitory concentrations (IC50s) as 21.5 and 29.7 μM respectively, and increased the colour intensities of the anthocyanins. Catechin and epicatechin did not inhibit the POD activity, while serving as POD substrates, with Km (the Michaelis constant) as 0.48 and 1.23 mM. Similar protein levels of the anthocyanin degradation-related 40-kDa PODs were detected in Brunfelsia and rose. In summary, high amount of tannins, particularly ECG and GCG, in red rose petals may inhibit the degradation-related enzymes, leading to the maintenance of anthocyanins in vivo.

Characterization of the action of tyrosinase on resorcinols

The action of tyrosinase on resorcinol and some derivatives (4-ethylresorcinol, 2-methylresorcinol and 4-methylresorcinol) was investigated. If the catalytic cycle is completed with a reductant such as ascorbic acid or an o-diphenol such as 4-tert-butylcatechol, these compounds act as substrates of tyrosinase in all cases. The reaction can also be carried out, adding hydrogen peroxide to the medium. All the above compounds were characterized as substrates of the enzyme and their kinetic constants, KM (Michaelis constant) and kcat (catalytic constant) were determined. Measurement of the activity of the enzyme after pre-incubation with resorcinol, 4-ethylresorcinol or 4-methylresorcinol points to an apparent loss of activity at short times, which could correspond to an enzymatic inactivation process. However, if the measurements are extended over longer times, a burst is observed and the enzymatic activity is recovered, demonstrating that these compounds are not suicide substrates of the enzyme. These effects are not observed with 2-methylresorcinol. The docking results indicate that the binding of met-tyrosinase with these resorcinols occurs in the same way, but not with 2-methylresorcinol, due to steric hindrance.

Extraction and Separation of Active Ingredients in Schisandra chinensis (Turcz.) Baill and the Study of their Antifungal Effects

Schisandra chinensis extracts (SEs) have traditionally been used as an oriental medicine for the treatment of various human diseases, however, their further application in the biocontrol of plant disease remains poorly understood. This study was conducted to develop eco-friendly botanical pesticides from extracts of S. chinensis and assess whether they could play a key role in plant disease defense. Concentrated active fractions (SE-I, SE-II, and SE-III) were obtained from S. chinensis via specific extraction and separation. Then, lignan-like substances, such as Schisanhenol B, were detected via High-Performance Liquid Chromatography-ElectroSpray Ionization-Mass Spectrometry (HPLC-ESI-MS) analyses of the active fractions. Moreover, the results from biological tests on colony growth inhibition and spore germination indicated that SE-I, SE-II, and SE-III could inhibit hyphal growth and spore generation of three important plant pathogenic fungi (Monilinia fructicola, Fusarium oxysporum, and Botryosphaeria dothidea). The study of the mechanisms of resistant fungi revealed that the oxidation resistance system, including reactive oxygen species (ROS), malondialdehyde (MDA), catalase (CAT), and superoxide dismutase (SOD), was activated. The expression of genes related to defense, such as pathogenesis-related protein (PR4), α-farnesene synthase (AFS), polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL) were shown to be up-regulated after treatment with SEs, which suggested an increase in apple immunity and that fruits were induced to effectively defend against the infection of pathogenic fungi (B. dothidea). This study revealed that SEs and their lignans represent promising resources for the development of safe, effective, and multi-targeted agents against pathogenic fungi.

The polyphenol oxidase gene family in poplar: phylogeny, differential expression and identification of a novel, vacuolar isoform

Polyphenol oxidases (PPOs) are oxidative enzymes that convert monophenols and o-diphenols to o-quinones using molecular oxygen. The quinone products are highly reactive following tissue damage and can interact with cellular constituents and cause oxidative browning and cross-linking. The induction of PPO in some plants as a result of wounding, herbivore attack, or pathogen infection has implicated them in defense. However, PPO-like enzymes that act as specific hydroxylases, for example in lignan and pigment biosynthesis, have also been discovered. Here, we present the first genome-enabled analysis of a PPO gene family. The Populus trichocarpa genome was found to contain a minimum of nine complete PPO genes, and seven of these were characterized further. The PPO gene family includes both recently duplicated and divergent sequences that are 36-98% identical at the amino acid level. Gene expression profiling in poplar tissues and organs revealed that the PPO genes are all differentially expressed during normal development, but that only a small subset of PPO genes are significantly upregulated by wounding, methyl jasmonate or pathogen infection. Our studies also identified PtrPPO13, a novel PPO gene that is predicted to encode an N-terminal signal peptide. Transient expression of green fluorescent protein fusions demonstrated its localization to the vacuolar lumen. Together, our findings show that the poplar PPO family is diverse and is likely linked to diverse physiological functions.

Activation of polyphenol oxidase in dormant wild oat caryopses by a seed-decay isolate of Fusarium avenaceum

Incubation of dormant wild oat (Avena fatua L., isoline M73) caryopses for 1-3 days with Fusarium avenaceum seed-decay isolate F.a.1 induced activity of the plant defense enzyme polyphenol oxidase (PPO). Both extracts and leachates obtained from F.a.1-treated caryopses had decreased abundance of an ∼57 kDa antigenic PPO and increased abundance of antigenic PPOs ranging from ∼52 to 14 kDa, as compared to extracts and leachates from untreated caryopsis. Leachates from caryopsis incubated for 2 days with F.a.1 also had 5.1- and 7.5-fold more total PPO activity/g fwt and specific activity, respectively. Fractionation of leachate proteins by ion-exchange chromatography associated the majority of PPO activity with an ∼36 kDa protein from untreated caryopses and ∼36, 25, and 24 kDa proteins from F.a.1-treated caryopses. Predicted peptide sequences obtained from high-performance liquid chromatography-tandem mass spectrometry analyses indicated that the ∼57 and 36 kDa wild oat proteins had a strong similarity to wheat PPO. However, the 25 and 24 kDa proteins were most similar to a Chitinase and oxalate oxidase, respectively. Our results indicate that F.a.1-induced activation of latent PPO in wild oat caryopsis likely involves a cleavage mechanism allowing activated PPOs to be readily mobilized into their surrounding environment.

Dehydration-related changes of peroxidase and polyphenol oxidase activity in fronds of the resurrection fern Asplenium ceterach L

Asplenium ceterach belongs to a group of poikilohydric ferns and it can recover uninjured from an almost completely dehydrated state. In our study, short term dehydration (24h) at four different water potentials, resulted in moderate water loss (partial desiccation) in fern tissue. The main phenolic acids represented in A. ceterach were chlorogenic (CGA) and caffeic acid (CA) and their content decreased during the dehydration process. For the first time, peroxidase (POD) and polyphenol oxidase (PPO) isoforms were determined in the rustyback fern. The results exhibit the presence of numerous anionic POD isoforms, with pI ranging from 4.4 to 5.8, but none of the cationic isoforms was detected. Two PPO isoforms were identified, one anionic with pI 6.3 and one cationic with pI of about 9.0. Short-term dehydration brought about a remarkable increase in POD and PPO activity using CGA as a substrate. Changes in enzyme activity and content of substrates during dehydration may play an important role in the adaptation of the rustyback fern to water deficit, and increase the overall plant resistance to stress conditions.