Biochemical properties of peroxidase from white and red cultivars of kolanut ( Cola nitida )

Biochemical properties of purified polyphenol oxidase from bitter leaf (Vernoniaamygdalina)

Polyphenol oxidase which is responsible for oxidative conversion of phenolic compounds to polymers, has continued to attract the attention of scientists. Here, we report the extraction, purification and biochemical properties of polyphenol oxidase (PPO) from bitter leaf (Vernonia amygdalina). The enzyme was purified and concentrated using a non-conventional approach, aqueous two-phase partitioning (ATPS) and the biochemical properties of the purified enzyme were investigated. Substrate specificity studies revealed that the enzyme predominantly exhibits diphenolase activity. The order of substrate preference was catechol > L-DOPA > caffeic acid > L-tyrosine > resorcinol>2-naphthol > phenol. The optimum pH and temperature obtained for the enzyme using catechol as substrate were 5.5 and 50 °C respectively. The estimated Michaelis constant (K_m) and maximum velocity (V_max) for the purified vaPPO using catechol as substrate were 183 ± 5.0 mM and 2000 ± 15 units/mg protein respectively. The catalytic efficiency (V_max/K_m) of the purified vaPPO was 10.9 ± 0.03 min/mg. Na⁺, K⁺ and Ba²⁺ remarkably activated the enzyme and the level of activation was proportional to the concentration. The vaPPO presented stability in the presence of up to 50 mM of the different metal ions tested. In contrast, Cu²⁺ and NH₄⁺ inhibited the enzyme even 10 mM concentrations. The enzyme was stable in chloroform retaining up to 60% relative activity at 50% (v/v) concentration. There was an increase in the activity (143%) of the enzyme at 30% (v/v) chloroform., revealing that vaPPO could catalyze the substrate more efficiently in 30% (v/v) chloroform. Total loss of enzyme activity was observed at 20% (v/v) concentrations of acetone, ethanol and methanol. In conclusion, the properties of the vaPPO such as its catalysis in the presence of organic solvents, metals and high temperature would be of interest in many biotechnological applications.

A minireview on the bioremediative potential of microbial enzymes as solution to emerging microplastic pollution

Accumulating plastics in the biosphere implicates adverse effects, raising serious concern among scientists worldwide. Plastic waste in nature disintegrates into microplastics. Because of their minute appearance, at a scale of <5 mm, microplastics easily penetrate different pristine water bodies and terrestrial niches, posing detrimental effects on flora and fauna. The potential bioremediative application of microbial enzymes is a sustainable solution for the degradation of microplastics. Studies have reported a plethora of bacterial and fungal species that can degrade synthetic plastics by excreting plastic-degrading enzymes. Identified microbial enzymes, such as IsPETase and IsMHETase from Ideonella sakaiensis 201-F6 and Thermobifida fusca cutinase (Tfc), are able to depolymerize plastic polymer chains producing ecologically harmless molecules like carbon dioxide and water. However, thermal stability and pH sensitivity are among the biochemical limitations of the plastic-degrading enzymes that affect their overall catalytic activities. The application of biotechnological approaches improves enzyme action and production. Protein-based engineering yields enzyme variants with higher enzymatic activity and temperature-stable properties, while site-directed mutagenesis using the Escherichia coli model system expresses mutant thermostable enzymes. Furthermore, microalgal chassis is a promising model system for "green" microplastic biodegradation. Hence, the bioremediative properties of microbial enzymes are genuinely encouraging for the biodegradation of synthetic microplastic polymers.

Studies on peroxidase from Moringa oleifera Lam leaves

Kinetic and physicochemical properties of Moringa oleifera peroxidase purified using a novel and cost efficient protocol was investigated with a view to providing information on its possible biotechnological potentials. Moringa oleifera peroxidase was purified to homogeneity in two steps, involving ATPS and size exclusion chromatography on Sephadex G-100 with a yield of 84.12 %. In-gel activity staining revealed the presence of one isoform of peroxidase. The purified peroxidase is monomeric with native and subunits molecular weight of 38.9 and 43.5 kDa respectively. Kinetic parameters - V _max, K _m(app) ^{o-dianisidine}, K _m(app) ^H ₂ ^O ₂ of the purified enzyme were 2.5 units/mg protein, 0.020 ± 0.04 mM and 1.37 ± 0.18 mM respectively. Its optimum pH and temperature were 5 and 30 °C respectively. The purified enzyme cross-linked BSA into an insoluble matrix with the aid of caffeic acid. The study concluded that the purification scheme adopted is rapid and efficient, the purified enzyme exhibited some physiochemical properties that make it suitable for various biotechnological applications.

Breakthroughs in the discovery and use of different peroxidase isoforms of microbial origin

Peroxidases are classified as oxidoreductases and are the second largest class of enzymes applied in biotechnological processes. These enzymes are used to catalyze various oxidative reactions using hydrogen peroxide and other substrates as electron donors. They are isolated from various sources such as plants, animals and microbes. Peroxidase enzymes have versatile applications in bioenergy, bioremediation, dye decolorization, humic acid degradation, paper and pulp, and textile industries. Besides, peroxidases from different sources have unique abilities to degrade a broad range of environmental pollutants such as petroleum hydrocarbons, dioxins, industrial dye effluents, herbicides and pesticides. Ironically, unlike most biological catalysts, the function of peroxidases varies according to their source. For instance, manganese peroxidase (MnP) of fungal origin is widely used for depolymerization and demethylation of lignin and bleaching of pulp. While, horseradish peroxidase of plant origin is used for removal of phenols and aromatic amines from waste waters. Microbial enzymes are believed to be more stable than enzymes of plant or animal origin. Thus, making microbially-derived peroxidases a well-sought-after biocatalysts for versatile industrial and environmental applications. Therefore, the current review article highlights on the recent breakthroughs in the discovery and use of peroxidase isoforms of microbial origin at a possible depth.