Microbial tyrosinases: promising enzymes for pharmaceutical, food bioprocessing, and environmental industry

Ectopic Expression of Production of Anthocyanin Pigment 1 (PAP1) Improves the Antioxidant and Anti-Melanogenic Properties of Ginseng (Panax ginseng C.A. Meyer) Hairy Roots

The development of genetically engineered cell cultures has been suggested as a potential approach for the production of target compounds from medicinal plants. In this study, we generated PAP1 (production of anthocyanin pigment 1)-overexpressing ginseng (Panax ginseng C.A. Meyer) hairy roots to improve the production of anthocyanins, as well as the bioactivity (e.g., antioxidant and whitening activities) of ginseng. Based on differentially expressed gene analysis, we found that ectopic expression of PAP1 induced the expression of genes involved in the ‘phenylpropanoid biosynthesis’ (24 genes), and ‘flavonoid biosynthesis’ (17 genes) pathways, resulting in 191- to 341-fold increases in anthocyanin production compared to transgenic control (TC) hairy roots. Additionally, PAP1-overexpressing ginseng hairy roots exhibited an approximately seven-fold higher DPPH-free radical scavenging activity and 10-fold higher ORAC value compared to the TC. In α-melanocyte-stimulating hormone-stimulated B16F10 cells, PAP1-overexpressing ginseng hairy roots strongly inhibited the accumulation of melanin by 50 to 59% compared to mock-control. Furthermore, results obtained by quantitative real-time PCR, western blot, and tyrosinase inhibition assay suggested that the anti-melanogenic activity of PAP1-overexpressing ginseng hairy roots is mediated by tyrosinase activity inhibition. Taken together, our results suggested that the ectopic expression of PAP1 is an effective strategy for the enhancement of anthocyanin production, which improves the biological activities of ginseng root cultures.

Marigold-like tyrosinase-embedded nanostructures-a nano-in-micro system

Marigold-like tyrosinase-entrenched nanostructures were developed by a facile method using a metal cofactor to overcome the limitations of conventional enzyme immobilization techniques. The protein-copper complex promotes the hierarchical self-assembly of nanopetals into marigold-like microstructures through a sequential germination process. Nanopetals, which originated from bead-like tiny projections, showed budding over the surface and promoted the anisotropic growth of copper phosphate nanocrystals upon co-ordination with the active functional groups in protein. This organic-inorganic hybrid showed excellent re-usability, comparable catalytic efficiency, faster reaction rate, improved storage, and thermal stability without affecting the enzyme activity.

Enzyme-catalysed polymer cross-linking: Biocatalytic tools for chemical biology, materials science and beyond

Intermolecular cross-linking is one of the most important techniques that can be used to fundamentally alter the material properties of a polymer. The introduction of covalent bonds between individual polymer chains creates 3D macromolecular assemblies with enhanced mechanical properties and greater chemical or thermal tolerances. In contrast to many chemical cross-linking reactions, which are the basis of thermoset plastics, enzyme catalysed processes offer a complimentary paradigm for the assembly of cross-linked polymer networks through their predictability and high levels of control. Additionally, enzyme catalysed reactions offer an inherently 'greener' and more biocompatible approach to covalent bond formation, which could include the use of aqueous solvents, ambient temperatures, and heavy metal-free reagents. Here, we review recent progress in the development of biocatalytic methods for polymer cross-linking, with a specific focus on the most promising candidate enzyme classes and their underlying catalytic mechanisms. We also provide exemplars of the use of enzyme catalysed cross-linking reactions in industrially relevant applications, noting the limitations of these approaches and outlining strategies to mitigate reported deficiencies.

Relationship of Agaricus bisporus mannose-binding protein to lectins with β-trefoil fold

Agaricus bisporus mannose-binding protein (Abmb) was discovered as part of the mushroom tyrosinase (PPO3) complex, but its function in the mushroom has remained obscure. The protein has a β-trefoil structure that is common for Ricin-B-like lectins. Indeed, its closest structural homologs are the hemagglutinin components of botulinum toxin (HA-33) and the Ricin-B-like lectin from Clitocybe nebularis (CNL), both of which bind galactose, and actinohivin, a recently discovered mannose-binding lectin from actinomycetes. Here we show that Abmb is evolutionarily related to them, which are lectins with a β-trefoil fold. We also show for the first time that Abmb can exhibit typical lectin agglutination activity but only when in the complex with mushroom tyrosinase. This is unexpected and unique because the two proteins are not evolutionarily related and have different activities. Lectin and tyrosinase major role in defense mechanism as well as Abmb and PPO3 gene regulation during the early stages of the development of mushroom fruiting bodies suggested that Abmb has likely a function in defense against bacterial infection and/or insect-induced damage.

A Coculture Based Tyrosine-Tyrosinase Electrochemical Gene Circuit for Connecting Cellular Communication with Electronic Networks

There is a growing interest in mediating information transfer between biology and electronics. By the addition of redox mediators to various samples and cells, one can both electronically obtain a redox "portrait" of a biological system and, conversely, program gene expression. Here, we have created a cell-based synthetic biology-electrochemical axis in which engineered cells process molecular cues, producing an output that can be directly recorded via electronics-but without the need for added redox mediators. The process is robust; two key components must act together to provide a valid signal. The system builds on the tyrosinase-mediated conversion of tyrosine to L-DOPA and L-DOPAquinone, which are both redox active. "Catalytic" transducer cells provide for signal-mediated surface expression of tyrosinase. Additionally, "reagent" transducer cells synthesize and export tyrosine, a substrate for tyrosinase. In cocultures, this system enables real-time electrochemical transduction of cell activating molecular cues. To demonstrate, we eavesdrop on quorum sensing signaling molecules that are secreted by Pseudomonas aeruginosa, N-(3-oxododecanoyl)-l-homoserine lactone and pyocyanin.

Engineering functional inorganic nanobiomaterials: controlling interactions between 2D-nanosheets and enzymes

A better understanding of the enzyme-nanosheet interface is imperative for the design of functional, robust inorganic nanobiomaterials and biodevices, now more than ever, for use in a broad spectrum of applications. This feature article discusses recent advances in controlling the enzyme-nanosheet interface with regards to α-zirconium(iv) phosphate (α-ZrP), graphene oxide (GO), graphene, and MoS₂ nanosheets. Specific focus will be placed on understanding the mechanisms with which these materials interact with enzymes and elaborate on particular ways to engineer and control these interactions. Our main discoveries include: (1) upon adsorption to the nanosheet surface, a decrease in the entropy of the enzyme's denatured state enhances stability; (2) proteins are used to create biophilic landing pads for increased enzyme stability on many different types of nanosheets; (3) proteins and enzymes are used as exfoliants by shear force to produce biofunctionalized nanosheet suspensions; and (4) bionfunctionalized nanosheets exhibit no acute toxicity. Recognizing proper methods to engineer the interface between enzymes and 2D-nanosheets, therefore, is an important step towards making green, sustainable, and environmentally conscious inorganic bionanomaterials for sensing, catalysis and drug delivery applications, as well as towards the successful manipulation of enzymes for advanced applications.

Biotechnology and Bioprocesses: Their Contribution to Sustainability

Significant advancements in biotechnology have resulted in the development of numerous fundamental bioprocesses, which have consolidated research and development and industrial progress in the field. These bioprocesses are used in medical therapies, diagnostic and immunization procedures, agriculture, food production, biofuel production, and environmental solutions (to address water-, soil-, and air-related problems), among other areas. The present study is a first approach toward the identification of scientific and technological bioprocess trajectories within the framework of sustainability. The method included a literature search (Scopus), a patent search (Patentscope), and a network analysis for the period from 2010 to 2019. Our results highlight the main technological sectors, countries, institutions, and academic publications that carry out work or publish literature related to sustainability and bioprocesses. The network analysis allowed for the identification of thematic clusters associated with sustainability and bioprocesses, revealing different related scientific topics. Our conclusions confirm that biotechnology is firmly positioned as an emerging knowledge area. Its dynamics, development, and outcomes during the study period reflect a substantial number of studies and technologies focused on the creation of knowledge aimed at improving economic development, environmental protection, and social welfare.

Histology of ex vivo skin after treatment with fractionated picosecond Nd:YAG laser in high and low-energy settings

Background: The fractionated picosecond laser produces microscopic lesions in the epidermis and dermis, which are known as laser-induced optical breakdown (LIOB) and intra-dermal laser-induced cavitation (LIC). There have been multiple histological reports on these phenomena, although some have been challenged on the grounds of similarity to artifacts. Asian skins, with a higher melanin content, may react differently to this treatment, and present literature is also lacking in this area.Purpose: To observe and report the histological effect of different energy levels and parameters of the fractional 532 nm/1064 nm picosecond laser on Asian skin ex vivo.Methods: Six skin samples were taken from clinically normal-looking perilesional areas and treated with different energy levels and parameters of the fractional 532 nm/1064 nm picosecond laser. The specimens were then sent to the lab for H&E staining, and the slides were reviewed by a dermatopathologist.Results: Superficial, intra-epidermal LIOBs were seen in skin treating at higher laser energies; deep, intra-dermal LICs were seen in skin treated at lower energies. Lesion sizes and depths were consistent with previously reported values on Caucasian skins, and lesions were spaced in 600-μm intervals or its multiple.Conclusions: The histological findings are consistent with results from other ethnicities, and the spacing of lesions is a strong indication of their validity as LIOBs or LICs.

Melanin biosynthesis in bacteria, regulation and production perspectives

The production of black pigments in bacteria was discovered more than a century ago and related to tyrosine metabolism. However, their diverse biological roles and the control of melanin synthesis in different bacteria have only recently been investigated. The broad distribution of these pigments suggests that they have an important role in a variety of organisms. Melanins protect microorganisms from many environmental stress conditions, ranging from ultraviolet radiation and toxic heavy metals to oxidative stress. Melanins can also affect bacterial interactions with other organisms and are important in pathogenesis and survival in many environments. Bacteria produce several types of melanin through dedicated pathways or as a result of enzymatic imbalances in altered metabolic routes. The control of the melanin synthesis in bacteria involves metabolic and transcriptional regulation, but many aspects remain still largely unknown. The diverse properties of melanins have spurred a large number of applications, and recent efforts have been done to produce the pigment at biotechnologically relevant scales.

Cantilever Nanobiosensor Functionalized with Tyrosinase for Detection of Estrone and β-estradiol in Water

This work aimed to develop cantilever nanobiosensor functionalized with tyrosinase enzyme to detect 17β-estradiol and estrone hormones. In this system, the tyrosinase enzyme was covalently immobilized by self-assembled monolayer onto the cantilever sensor surface. It was possible to verify that the high hormone concentration investigated resulted in high voltage response. The nanobiosensor presented a distinction between the concentrations evaluated and was verified sensitivities of 0.497 and 0.101 V/μg, limit of detection of 0.1 and 0.4 ng/L for the hormones 17β-estradiol and estrone, respectively. The device showed good reversibility and during 30 days of storage maintained about 99% of the original signal. The cantilever nanobiosensor applied in different water samples (ultrapure, river, tap, and mineral) showed good performance, so could be readily extended toward the on-site monitoring of the other trace small molecular pollutants in environmental water matrices.

Phenolic Compounds from the Aerial Parts of Blepharis linariifolia Pers. and Their Free Radical Scavenging and Enzyme Inhibitory Activities

Background:Blepharis linariifolia Pers. (Family: Acanthaceae) is used in traditional medicines as a general tonic and for the treatment of various health problems in Sudan. The main aim of this study was to isolate and identify the major chemical constituents from the aerial parts of B. linariifolia and evaluate their bioactivities. Methods: The dried aerial parts of the plant were extracted successively with 100% acetone and 50% acetone, and thereafter the combined extract was subjected to repeated column chromatography to isolate the main components. Free radical scavenging activity was evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical method, and in vitro enzyme inhibitory activities against α-glucosidase, pancreatic lipase, and mushroom tyrosinase were evaluated. Results: From the detailed chemical analysis, verbascoside (1), vanillic acid (2), apigenin (3), and 6″-O-p-coumaroylprunin (4), were isolated and their structures were identified on the basis of their nuclear magnetic resonance (NMR) spectral data. Among the isolated compounds, verbascoside (1) showed the most potent free radical scavenging activity (IC50 = 22.03 ± 0.04 μM). Apigenin (3) and 6″-O-p-coumaroylprunin (4) showed promising inhibitory activities against all tested enzymes. Apigenin (3) showed the most potent inhibitory activity against α-glucosidase and tyrosinase (IC50 = 34.73 ± 1.78 μM and 23.14 ± 1.83 μM, respectively), whereas 6″-O-p-coumaroylprunin (4) showed potent inhibition for lipase (IC50 = 2.25 ± 0.17 μM). Conclusions: Four phenolic compounds were isolated and identified from B. linariifolia acetone extract, which are reported for the first time from this plant. All compounds showed good DPPH free radical scavenging activities, with verbascoside (1) being the most potent. Apigenin (3) was the most active as α-glucosidase and mushroom tyrosinase inhibitor, while 6″-O-p-coumaroylprunin (4) showed potent inhibitory activity for pancreatic lipase.

Biologically active compounds from two members of the Asteraceae family: Tragopogon dubius Scop. and Tussilago farfara L

Tragopogon dubius and Tussilago farfara are consumed as vegetables and used in folk medicine to manage common diseases. Herein, the chemical compositions and biological activities of different leaf extracts (ethyl acetate, methanol, and water) of T. dubius and T. farfara were evaluated. The antibacterial, antifungal, and antioxidant abilities of the extracts were tested using different assays including free radical scavenging, reducing power, phosphomolybdenum, and metal chelating assays. Enzyme inhibitory potentials were evaluated against cholinesterases, tyrosinase, α-amylase and α-glucosidase. Complexes of bioactive compounds (chlorogenic and rosmarinic acid) were docked into the enzymatic cavity of α-glucosidase and subjected to molecular dynamic calculation, enzyme conformational stability, and flexibility analysis. T. dubius and T. farfara extracts showed remarkable antioxidant potentials. Ethyl acetate extracts of T. dubius and T. farfara were the most potent inhibitors of acetylcholinesterase and butyrylcholinesterase. T. dubius ethyl acetate extract and T. farfara methanolic extract showed noteworthy activity against α-glucosidase. High performance liquid chromatography analysis revealed the abundance of some phenolic compounds including chlorogenic and rosmarinic acids. Ethyl acetate extract of T. dubius showed notable antifungal activity against all strains. Docking studies showed best pose for chlorogenic acid was stabilized by a network of hydrogen bonds with residues Asp1157, Asp1279, whereas rosmarinic acid showed several hydrogen bonds with Asp1157, Asp1420, Asp1526, Lys1460 and Trp1369. This study further validates the use of T. dubius and T. farfara in traditional medicine, as well as act as a stimulus for further studies for future biomedicine development. Communicated by Ramaswamy H. Sarma.

Novel Bacillus subtilis Spore-Displayed Tyrosinase Kit for Rapid Detection of Tyrosine in Urine: Pharmaceutical Applications for the Early Diagnosis of Kidney-Related Diseases

Purpose: Simple and cheap diagnostic kit development is one of the important aims of pharmaceutical developers and companies focused on public health improvement. The Bacillus subtilis spore surface-display technique is a genetic engineering method that is used to develop new-generation diagnostic kits applicable for the early detection of various types of diseases. In this study, we developed a novel simple, rapid, and inexpensive diagnostic paper-based kit to detect tyrosine in urine samples of humans and animals that is applicable for home or laboratory use.

Methods: The B. subtilis spore-displayed tyrosinase system developed by genetic engineering methods was used to prepare a paper-based kit to detect tyrosine in urine samples of different groups of patients (i.e., patients with diabetes, diabetes with chronic kidney disease (CKD), and chronic kidney disease) for the detection of tyrosine during the acute disease phase. To confirm the sensitivity and specificity of the kit, tyrosine was also detected in urine samples using conventional liquid chromatography/mass spectroscopy.

Results: Different concentrations of tyrosine (0.1–1 mM) were detected in urine samples based on visible changes of color from bright brownish-gray to dark brownish-gray within 1 hour. The kit could screen samples to distinguish the three groups of patients based on formation of a broad spectrum of colors reflecting the concentration of tyrosine.

Conclusion: To the best of our knowledge, this is the first diagnostic kit with potential to rapidly diagnose various diseases related to the production of tyrosine in biological samples. This kit is not only widely applicable, including for personal use in the home, but is also appropriate as a part of standard screening tests and health protection programs in countries with limited resources.

Aptitude of Oxidative Enzymes for Treatment of Wastewater Pollutants: A Laccase Perspective

Natural water sources are very often contaminated by municipal wastewater discharges which contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both, which frustrates the universal millenium development goal of provision of the relatively scarce pristine freshwater to water-scarce and -stressed communities, in order to augment their socioeconomic well-being. Seeing that both regulatory measures, as regards the discharge limits of wastewater, and the query for efficient treatment methods remain unanswered, partially, the prospects of enzymatic treatment of wastewater is advisable. Therefore, a reconsideration was assigned to the possible capacity of oxidative enzymes and the respective challenges encountered during their applications in wastewater treatment, and ultimately, the prospects of laccase, a polyphenol oxidase that oxidizes aromatic and inorganic substrates with electron-donating groups in treatment aromatic contaminants of wastewater, in real wastewater situations, since it is assumed to be a vehicle for a greener community. Furthermore, the importance of laccase-driven catalysis toward maintaining mass-energy balance, hence minimizing environmental waste, was comprehensibly elucidated, as well the strategic positioning of laccase in a model wastewater treatment facility for effective treatment of wastewater contaminants.

Highly efficient biocatalytic synthesis of L-DOPA using in situ immobilized Verrucomicrobium spinosum tyrosinase on polyhydroxyalkanoate nano-granules

L-DOPA (3,4-dihydroxyphenyl-L-alanine) is a preferred drug for Parkinson's disease, and is currently in great demand every year worldwide. Biocatalytic conversion of L-tyrosine by tyrosinases is the most promising method for the low-cost production of L-DOPA in both research and industry. Yet, it has been hampered by low productivity, low conversion rate, and low stability of the biocatalyst, tyrosinase. An alternative tyrosinase TyrVs from Verrucomicrobium spinosum with more efficient expression in heterologous host and better stability than the commercially available Agaricus bisporus tyrosinase was identified in this study. Additionally, it was prepared as a novel nano-biocatalyst based on the distinct one-step in situ immobilization on the surface of polyhydroxyalkanoate (PHA) nano-granules. The resulting PHA-TyrVs nano-granules demonstrated improved L-DOPA-forming monophenolase activity of 9155.88 U/g (Tyr protein), which was 3.19-fold higher than that of free TyrVs. The nano-granules also exhibited remarkable thermo-stability, with an optimal temperature of 50 °C, and maintained more than 70% of the initial activity after incubation at 55 °C for 24 h. And an enhanced affinity of copper ion was observed in the PHA-TyrVs nano-granules, making them even better biocatalysts for L-DOPA production. Therefore, a considerable productivity of L-DOPA, amounting to 148.70 mg/L h, with a conversion rate of L-tyrosine of 90.62% can be achieved by the PHA-TyrVs nano-granules after 3 h of biocatalysis under optimized conditions, without significant loss of enzyme activity or L-DOPA yield after 8 cycles of repeated use. Our study provides an excellent and robust nano-biocatalyst for the cost-effective production of L-DOPA.

Optimization of Bacillus licheniformis MAL tyrosinase: in vitro anticancer activity for brown and black eumelanin

The influence of tyrosinase in catalyzes/stimulates the eumelanin production was studied. Accordingly, bacterial sp. was isolated and identified as Bacillus licheniformis based on 16S rRNA. It could grow and gave monophenolase and diphenolase productivity in medium contained tyrosin and Cu²⁺ only. The tyrosinase enzymes were optimized by studying different environmental and nutritional factors. The maximum monophenolase and diphenolase productivity were obtained at 60 °C, pH9, Cu²⁺(0.01g), liver extract (1 g/L) and the oxygen level fixed at 20%. Also, the mannose as a carbon source increased the monophenolase production 6.2 times. For the first time, two types of eumelanin were extracted by hydrochloric acid treatment. The black and brown eumelanin weighed (0.1 g/100 mL and 0.7 g/100 mL respectively) and characterized by using FTIR and UV/Vis spectroscopy techniques. Their morphological structure and its elemental composition were characterized by SEM and EDAX respectively. The black melanin showed promising anticancer activity towards HEPG-2 and HCT-116 cell lines with IC₅₀ values (6.15, 5.54 μg) compared to Doxorubicin (4.05, 4.45 μg) respectively.

Concise Modular Synthesis of Thalassotalic Acids A-C

The novel N-acyldehydrotyrosine analogues known as thalassotalic acids A-C were isolated from a marine bacterium by Deering et al. in 2016. These molecules were shown to have tyrosinase inhibition activity and thus are an attractive set of molecules for further study and optimization. To this end, a concise and modular synthesis has been devised and executed to produce thalassotalic acids A-C and two unnatural analogues. This synthesis has confirmed the identity and inhibitory data of thalassotalic acids A-C, more potent synthetic analogues (IC₅₀ = 65 μM), and provides a route for further structure-activity relationship studies to optimize these molecules.

Development of a Novel Biosensor Based on Tyrosinase/Platinum Nanoparticles/Chitosan/Graphene Nanostructured Layer with Applicability in Bioanalysis

The present paper describes the preparation and characterization of a graphene, chitosan, platinum nanoparticles and tyrosinase-based bionanocomposite film deposited on the surface of a screen-printed carbon electrode for the detection of L-tyrosine by voltammetry. The redox process on the biosensor surface is associated with the enzymatic oxidation of L-tyrosine, which is favoured by graphene and platinum nanoparticles that increase electrical conductivity and the electron transfer rate. Chitosan ensures the biocompatibility between the tyrosinase enzyme and the solid matrix, as well as a series of complex interactions for an efficient immobilization of the biocatalyst. Experimental conditions were optimized so that the analytical performances of the biosensor were maximal for L-tyrosine detection. By using square wave voltammetry as the detection method, a very low detection limit (4.75 × 10⁻⁸ M), a vast linearity domain (0.1–100 μM) and a high affinity of the enzyme for the substrate (K_M^app is 53.4 μM) were obtained. The repeatability of the voltammetric response, the stability, and the reduced interference of the chemical species present in the sample prove that this biosensor is an excellent tool to be used in bioanalysis. L-tyrosine detection in medical and pharmaceutical samples was performed with very good results, the analytical recovery values obtained being between 99.5% and 101%. The analytical method based on biosensor was validated by the standard method of analysis, the differences observed being statistically insignificant at the 99% confidence level.

Catecholic Compounds in Ctenophore Colloblast and Nerve Net Proteins Suggest a Structural Role for DOPA-Like Molecules in an Early-Diverging Animal Lineage

Ctenophores, or comb jellies, are among the earliest-diverging extant animal lineages. Several recent phylogenomic studies suggest that they may even be the sister group to all other animals. This unexpected finding remains difficult to contextualize, particularly given ctenophores' unique and sometimes poorly understood physiology. Colloblasts, a ctenophore-specific cell type found on the surface of these animals' tentacles, are emblematic of this difficulty. The exterior of the colloblast is dotted with granules that burst and release an adhesive on contact with prey, ensnaring it for consumption. To date, little is known about the fast-acting underwater adhesive that these cells secrete or its biochemistry. We present evidence that proteins in the colloblasts of the ctenophore Pleurobrachia bachei incorporate catecholic compounds similar to the amino acid l-3,4-dihydroxyphenylalanine. These compounds are associated with adhesive-containing granules on the surface of colloblasts, suggesting that they may play a role in prey capture, akin to dihydroxyphenylalanine-based adhesives in mussel byssus. We also present unexpected evidence of similar catecholic compounds in association with the subepithelial nerve net. There, catecholic compounds are present in spatial patterns similar to those of l-3,4-dihydroxyphenylalanine and its derivatives in cnidarian nerves, where they are associated with membranes and possess unknown functionality. This "structural" use of catecholic molecules in ctenophores represents the earliest-diverging animal lineage in which this trait has been observed, though it remains unclear whether structural catechols are deeply rooted in animals or whether they have arisen multiple times.

Polyserotonin Nanoparticles as Multifunctional Materials for Biomedical Applications

Serotonin-based nanoparticles represent a class of previously unexplored multifunctional nanoplatforms with potential biomedical applications. Serotonin, under basic conditions, self-assembles into monodisperse nanoparticles via autoxidation of serotonin monomers. To demonstrate potential applications of polyserotonin nanoparticles for cancer therapeutics, we show that these particles are biocompatible, exhibit photothermal effects when exposed to near-infrared radiation, and load the chemotherapeutic drug doxorubicin, releasing it contextually and responsively in specific microenvironments. Quantum mechanical and molecular dynamics simulations were performed to interrogate the interactions between surface-adsorbed drug molecules and polyserotonin nanoparticles. To investigate the potential of polyserotonin nanoparticles for in vivo targeting, we explored their nano-bio interfaces by conducting protein corona experiments. Polyserotonin nanoparticles had reduced surface-protein interactions under biological conditions compared to polydopamine nanoparticles, a similar polymer material widely investigated for related applications. These findings suggest that serotonin-based nanoparticles have advantages as drug-delivery platforms for synergistic chemo- and photothermal therapy associated with limited nonspecific interactions.

Screening and Characterizing Tyrosinase Inhibitors from Salvia miltiorrhiza and Carthamus tinctorius by Spectrum-Effect Relationship Analysis and Molecular Docking

Tyrosinase (TYR) is a rate-limiting enzyme in the synthesis of melanin, while direct TYR inhibitors are a class of important clinical antimelanoma drugs. This study established a spectrum-effect relationship analysis method and high-performance liquid chromatography-mass spectrometry (LC-MS) analysis method to screen and identify the active ingredients that inhibited TYR in Salvia miltiorrhiza-Carthamus tinctorius (Danshen-Honghua, DH) herbal pair. Seventeen potential active compounds (peaks) in the extract of DH herbal pair were predicted, and thirteen of them were tentatively identified by LC-MS analysis. Furthermore, TYR inhibitory activities of five pure compounds obtained from the DH herbal pair were validated in the test in which kojic acid served as a positive control drug. Among them, three compounds including protocatechuic aldehyde, hydroxysafflor yellow A, and tanshinone IIA were verified to have high TYR inhibitory activity (IC50 value of 455, 498, and 1214 μM, resp.) and bind to the same amino acid residues in TYR catalytic pocket according to the results of the molecular docking test. However, the other two compounds lithospermic acid and salvianolic acid A had a weak effect on TYR, as they do not combine with the active amino acid residues or act on the active center of TYR. Therefore, the developed methods (spectrum-effect relationship analysis and molecular docking) could be used to effectively screen TYR inhibitors in complex mixtures such as natural products.

Phytochemical characterization,in vitroandin silicoapproaches for threeHypericumspecies

Members of theHypericumgenus are spread throughout the world and have a long history of use in traditional systems of medicines.

Biochemical aspects of mammalian melanocytes and the emerging role of melanocyte stem cells in dermatological therapies

Skin color in animals is richer than human beings and is determined by different types of pigments. Melanin is the key pigment responsible for the diverse pigmentation found in animal and human skin, hair, and eyes. Melanin pigment is synthesized by melanocytes and is consecutively transferred to adjacent keratinocytes; here, it acts as an internal sunscreen to defend from ultraviolet (UV) damage. Any defect in the process of melanocytes development and/or melanin synthesis results in esthetic problem of abnormal pigmentation. Clinically, abnormal pigmentation displays distinct increased or reduced pigment levels, known as hyperpigmentation or hypopigmentation. These defects affect either the melanocyte number or its function. Herein, we discuss the fundamental aspects of melanocytes/melanin biology taken together the underlying cause of pigmentary disorders. The current chapter also gives an insight into the melanocyte stem cells biology, which in turn can facilitate the development of novel treatment regimens for dermatological disorders.

Isolation and characterization of a novel tyrosinase produced by Sahara soil actinobacteria and immobilization on nylon nanofiber membranes

In the present study different actinomycete strains were collected and isolated from Algerian Sahara soil with the aim to select novel enzymes with promising features for biotechnological applications. The Ms1 strain was selected, amongst the others, for its capability to produce melanin in different solid media. Ms1 chromosomal DNA was sequenced and the strain assigned to Streptomyces cyaneofuscatus sp. A tyrosinase (MW∼30kD) encoding sequence was identified and the corresponding enzyme was isolated and biochemically characterized. The tyrosinase showed the highest activity and stability at neutral and alkaline pH and it was able to oxidize l-DOPA at T=55°C and pH 7. The enzyme showed variable stability in presence of various water-miscible organic solvents, while it was inactivated by reducing agents. The tyrosinase activity was unaffected by NaCl and enhanced by different cations. Furthermore, the enzyme showed a higher specificity for diphenols than monophenols showing a higher diphenolase than monophenolase activity. Finally, tyrosinase was stabilized by immobilization on nylon nanofiber membranes with a payload of 82% when 1% glutaraldeyde was used. Taken all together, these results show that the enzyme displays interesting properties for biotechnological purposes.

Robust Nonlinear Regression in Enzyme Kinetic Parameters Estimation

Accurate estimation of essential enzyme kinetic parameters, such as Km and Vmax, is very important in modern biology. To this date, linearization of kinetic equations is still widely established practice for determining these parameters in chemical and enzyme catalysis. Although simplicity of linear optimization is alluring, these methods have certain pitfalls due to which they more often then not result in misleading estimation of enzyme parameters. In order to obtain more accurate predictions of parameter values, the use of nonlinear least-squares fitting techniques is recommended. However, when there are outliers present in the data, these techniques become unreliable. This paper proposes the use of a robust nonlinear regression estimator based on modified Tukey’s biweight function that can provide more resilient results in the presence of outliers and/or influential observations. Real and synthetic kinetic data have been used to test our approach. Monte Carlo simulations are performed to illustrate the efficacy and the robustness of the biweight estimator in comparison with the standard linearization methods and the ordinary least-squares nonlinear regression. We then apply this method to experimental data for the tyrosinase enzyme (EC 1.14.18.1) extracted from Solanum tuberosum, Agaricus bisporus, and Pleurotus ostreatus. The results on both artificial and experimental data clearly show that the proposed robust estimator can be successfully employed to determine accurate values of Km and Vmax.

Microbial enzymes: industrial progress in 21st century

Abstract

Biocatalytic potential of microorganisms have been employed for centuries to produce bread, wine, vinegar and other common products without understanding the biochemical basis of their ingredients. Microbial enzymes have gained interest for their widespread uses in industries and medicine owing to their stability, catalytic activity, and ease of production and optimization than plant and animal enzymes. The use of enzymes in various industries (e.g., food, agriculture, chemicals, and pharmaceuticals) is increasing rapidly due to reduced processing time, low energy input, cost effectiveness, nontoxic and eco-friendly characteristics. Microbial enzymes are capable of degrading toxic chemical compounds of industrial and domestic wastes (phenolic compounds, nitriles, amines etc.) either via degradation or conversion. Here in this review, we highlight and discuss current technical and scientific involvement of microorganisms in enzyme production and their present status in worldwide enzyme market.

Graphical abstract

Non-specific binding sites help to explain mixed inhibition in mushroom tyrosinase activities

Inhibition and activation studies of tyrosinase could prove beneficial to agricultural, food, cosmetic, and pharmaceutical industries. Although non-competitive and mixed-inhibition are frequent modes observed in kinetics studies on mushroom tyrosinase (MT) activities, the phenomena are left unexplained. In this study, dual effects of phthalic acid (PA) and cinnamic acid (CA) on MT during mono-phenolase activity were demonstrated. PA activated and inhibited MT at concentrations lower and higher than 150 μM, respectively. In contrast, CA inhibited and activated MT at concentrations lower and higher than 5 μM. The mode of inhibition for both effectors was mixed-type. Complex kinetics of MT in the presence of a modulator could partly be ascribed to its mixed-cooperativity. However, to explain mixed-inhibition mode, it is necessary to demonstrate how the ternary complex of substrate/enzyme/effector is formed. Therefore, we looked for possible non-specific binding sites using MT tropolone-bound PDB (2Y9X) in the computational studies. When tropolone was in MTPa (active site), PA and CA occupied different pockets (named MTPb and MTPc, respectively). The close Moldock scores of PA binding posed in MTPb and MTPa suggested that MTPb could be a secondary binding site for PA. Similar results were obtained for CA. Ensuing results from 10 ns molecular dynamics simulations for 2Y9X-effector complexes indicated that the structures were gradually stabilized during simulation. Tunnel analysis by using CAVER Analyst and CHEXVIS resulted in identifying two distinct channels that assumingly participate in exchanging the effectors when the direct channel to MTPa is not accessible.

Enzymes as Green Catalysts for Precision Macromolecular Synthesis

The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.

Inhibitory effects of α-Na8SiW11CoO40 on tyrosinase and its application in controlling browning of fresh-cut apples

α-Na8SiW11CoO40 was synthesized and characterized. The inhibitory effects of α-Na8SiW11CoO40 on the activity of mushroom tyrosinase and the effects of α-Na8SiW11CoO40 on the browning of fresh-cut apples were studied. The Native-PAGE result showed that α-Na8SiW11CoO40 had a significant inhibitory effect on tyrosinase. Kinetic analyses showed that α-Na8SiW11CoO40 was an irreversible and competitive inhibitor. The inhibitor concentration leading to a 50% reduction in activity (IC50) was estimated to be 0.239 mM. Additionally, the results also showed that α-Na8SiW11CoO40 treatment could significantly decrease the browning process of apple slices and inhibit the polyphenol oxidase (PPO) activity. Moreover, application of α-Na8SiW11CoO40 resulted in higher peroxidase activity and promoted high amounts of phenolic compounds and ascorbic acid. This study may provide a promising method for the use of polyoxometalates to inhibit tyrosinase activity and control the browning of fresh-cut apples.

Hair dyes resorcinol and lawsone reduce production of melanin in melanoma cells by tyrosinase activity inhibition and decreasing tyrosinase and microphthalmia-associated transcription factor (MITF) expression

Hair coloring products are one of the most important cosmetics for modern people; there are three major types of hair dyes, including the temporary, semi-permanent and permanent hair dyes. The selected hair dyes (such as ammonium persulfate, sodium persulfate, resorcinol and lawsone) are the important components for hair coloring products. Therefore, we analyzed the effects of these compounds on melanogenesis in B16-F10 melanoma cells. The results proved that hair dyes resorcinol and lawsone can reduce the production of melanin. The results also confirmed that resorcinol and lawsone inhibit mushroom and cellular tyrosinase activities in vitro. Resorcinol and lawsone can also downregulate the protein levels of tyrosinase and microphthalmia-associated transcription factor (MITF) in B16-F10 cells. Thus, we suggest that frequent use of hair dyes may have the risk of reducing natural melanin production in hair follicles. Moreover, resorcinol and lawsone may also be used as hypopigmenting agents to food, agricultural and cosmetic industry in the future.

Purification and characterization of melanogenic enzyme tyrosinase from button mushroom

Melanogenesis is a biosynthetic pathway for the formation of the pigment melanin in human skin. A key enzyme, tyrosinase, catalyzes the first and only rate-limiting steps in melanogenesis. Since the discovery of its melanogenic properties, tyrosinase has been in prime focus and microbial sources of the enzyme are sought. Agaricus bisporus widely known as the common edible mushroom, it's taking place in high amounts of proteins, enzyme, carbohydrates, fibers, and low fat contents are frequently cited in the literature in relation to their nutritional value. In the present study tyrosinase from Agaricus bisporus was purified by ammonium sulphate precipitation, dialysis followed by gel filtration chromatography on Sephadex G-100, and ion exchange chromatography on DEAE-Cellulose; the enzyme was purified, 16.36-fold to give 26.6% yield on total activity in the crude extract and final specific activity of 52.19 U/mg. The SDS-PAGE electrophoresis showed a migrating protein band molecular weight of 95 kDa. The purified tyrosinase was optimized and the results revealed that the optimum values are pH 7.0 and temperature 35°C. The highest activity was reported towards its natural substrate, L-DOPA, with an apparent Km value of 0.933 mM. This indicated that tyrosinase purified from Agaricus bisporus is a potential source for medical applications.