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

Overview on tyrosinases: Genetics, molecular biology, phylogenetic relationship

Tyrosinases (TYRs) are enzymes found in various organisms that are crucial for melanin biosynthesis, coloration, and UV protection. They play vital roles in insect cuticle sclerotization, mollusk shell formation, fungal and bacterial pigmentation, biofilm formation, and virulence. Structurally, TYRs feature copper-binding sites that are essential for catalytic activity, facilitating substrate oxidation via interactions with conserved histidine residues. TYRs exhibit diversity across animals, plants, fungi, mollusks, and bacteria, reflecting their roles and function. Eukaryotic TYRs undergo post-translational modifications, such as glycosylation, which affect protein folding and activity. Bacterial TYRs are categorized into five types based on their structural variation, domain organization and enzymatic properties, showing versatility across bacterial species. Moreover, bacterial TYRs, akin to fungal TYRs, have been implicated in the synthesis of secondary metabolites with antimicrobial properties. TYRs share significant sequence homology with hemocyanins, oxygen-carrier proteins in mollusks and arthropods, highlighting their evolutionary relationships. The evolution of TYRs underscores the dynamic nature of these enzymes and reflects adaptive strategies across diverse taxa.

Exploring the Agricultural Applications of Microbial Melanin

Microbial melanins are a group of pigments with protective effects against harsh conditions, showing fascinating photoprotective activities, mainly due to their capability to absorb UV radiation. In bacteria, they are produced by the oxidation of L-tyrosine, generating eumelanin and pheomelanin. Meanwhile, allomelanin is produced by fungi through the decarboxylative condensation of malonyl-CoA. Moreover, melanins possess antioxidant and antimicrobial activities, revealing significant properties that can be used in different industries, such as cosmetic, pharmaceutical, and agronomical. In agriculture, melanins have potential applications, including the development of new biological products based on this pigment for the biocontrol of phytopathogenic fungi and bacteria to reduce the excessive and toxic levels of agrochemicals used in fields. Furthermore, there are possibilities to develop and improve new bio-based pesticides that control pest insects through the use of melanin-producing and toxin-producing Bacillus thuringiensis or through the application of melanin to insecticidal proteins to generate a new product with improved resistance to UV radiation that can then be applied to the plants. Melanins and melanin-producing bacteria have potential applications in agriculture due to their ability to improve plant growth. Finally, the bioremediation of water and soils is possible through the application of melanins to polluted soils and water, removing synthetic dyes and toxic metals.

Crotalaria burhia Buch. -Ham.: a comprehensive review of its botany, traditional uses, phytochemistry, and pharmacology

Crotalaria burhia (Family: Fabaceae) is an important medicinal plant widely distributed in arid parts of the world, including Pakistan, India, and Afghanistan. This plant has enormous ethnobotanical values and is used to treat various common ailments such as swelling, infections, cancer, hydrophobia, pain and skin diseases. Moreover, it is also utilised as food for goats, to make sheds for animals and as a suitable soil binder. This review article is an attempt to analyse critically and to provide updated and categorised information about C. burhia including comprehensive knowledge of the botanical description, traditional/folklore uses, phytochemistry, pharmacological/biological potential, and to facilitate scientific basis for future work. The phytochemical studies (qualitative and quantitative) on C. burhia have indicated the presence of important phytochemical classes, namely alkaloids, flavonoids, glycosides, saponins, phenolics, tannins, steroids, and terpenoids. Pharmacological studies such as anti-inflammatory/analgesic, antioxidant, anti-microbial, anti-tumour, anti-nociceptive, enzyme inhibition, and termiticidal activities were reported from different parts of this plant. Most of the bioassays from this plant have been done on the crude extract. Minimal information about the phytochemicals (responsible for biological activities), except a few compounds has been reported. The potential chemical compounds may need to be purified and tested for the biological potential from isolated compounds in future.

Alternative strategies for the recombinant synthesis, DOPA modification and analysis of mussel foot proteins - A case study for Mefp-3 from Mytilus edulis

Mussel foot proteins (Mfps) possess unique binding properties to various surfaces due to the presence of L-3,4-dihydroxyphenylalanine (DOPA). Mytilus edulis foot protein-3 (Mefp-3) is one of several proteins in the byssal adhesive plaque. Its localization at the plaque-substrate interface approved that Mefp-3 plays a key role in adhesion. Therefore, the protein is suitable for the development of innovative bio-based binders. However, recombinant Mfp-3s are mainly purified from inclusion bodies under denaturing conditions. Here, we describe a robust and reproducible protocol for obtaining soluble and tag-free Mefp-3 using the SUMO-fusion technology. Additionally, a microbial tyrosinase from Verrucomicrobium spinosum was used for the in vitro hydroxylation of peptide-bound tyrosines in Mefp-3 for the first time. The highly hydroxylated Mefp-3, confirmed by MALDI-TOF-MS, exhibited excellent adhesive properties comparable to a commercial glue. These results demonstrate a concerted and simplified high yield production process for recombinant soluble and tag-free Mfp3-based proteins with on demand DOPA modification.

Tyrosinase-based nanobiosensor for environmental monitoring of hormones in river water

This study explores the application of a tyrosinase cantilever nanobiosensor for detecting 17β-estradiol and estrone in typical water systems. The physical-chemical parameters of water were evaluated within the Tigre River micro-basin in Erechim, RS, to determine water potability for urban populations. Water clarity, conductivity, and pH levels were essential markers, adhering to recognized standards for water quality and human consumption. The cantilever nanobiosensor demonstrated strong sensitivity and a broad linear range, with a limit of detection (<0.00051 ppb) surpassing other enzymatic biosensors and covering a range of 0.0001-100 ppb. The real water sample quality investigated in relation to contamination with 17β-estradiol and estrone by nanobiosensor showed values below the LOD for both compounds. Recovery studies demonstrated the reliability of the nanobiosensor. Selectivity tests indicated minimal interference from structurally similar substances. This study validates the nanobiosensor's potential for environmental monitoring and hormone detection, aligning with standard practices.

Biochemical and In Silico Studies on Triazole Derivatives as Tyrosinase Inhibitors: Potential Treatment of Hyperpigmentation Related Skin Disorders

INTRODUCTION

Tyrosinase is a versatile, glycosylated copper-containing oxidase enzyme that mainly catalyzes the biosynthesis of melanin in mammals. Its overexpression leads to the formation of excess melanin, resulting in hyperpigmentary skin disorders, such as dark spots, melasma, freckles, etc. Therefore, inhibition of tyrosinase is a therapeutic approach for the treatment of hyperpigmentation.

METHODS

The current study focused on evaluating tyrosinase inhibitory activities of triazole derivatives 1-20, bearing different substituents on the phenyl ring. 17 derivatives have shown a potent tyrosinase inhibition with IC50 values between 1.6 to 13 μM, as compared to the standard drug, i.e., kojic acid (IC50 = 24.1 ± 0.5 μM). Particularly, compounds 11 and 15 displayed 12 times more potent inhibitory effects than the kojic acid.

RESULTS

The structure-activity relationship revealed that substituting halogens at the C-4 position of the benzene ring renders remarkable anti-tyrosinase activities. Compounds 1-3 and 8 showed a competitive type of inhibition, while compounds 5, 11, and 15 showed a non-competitive mode of inhibition. Next, we performed molecular docking analyses to study the binding modes and interactions between the ligands (inhibitors) and the active site of the tyrosinase enzyme (receptor). Besides this, we have assessed the toxicity profile of inhibitors on the BJ human fibroblast cell line.

CONCLUSION

The majority of the newly identified tyrosinase inhibitors were found to be noncytotoxic. The results presented herein form the basis of further studies on triazole derivatives as potential drug leads against tyrosinase-related diseases.

Potent inhibition of human tyrosinase inhibitor by verproside from the whole plant of Pseudolysimachion rotundum var. subintegrum

Affinity-based ultrafiltration-mass spectrometry coupled with ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry was utilised for the structural identification of direct tyrosinase ligands from a crude Pseudolysimachion rotundum var. subintegrum extract. False positives were recognised by introducing time-dependent inhibition in the control for comparison. The P. rotundum extract contained nine main metabolites in the UPLC-QTOF-MS chromatogram. However, four metabolites were reduced after incubation with tyrosinase, indicating that these metabolites were bound to tyrosinase. The IC50 values of verproside (1) were 31.2 µM and 197.3 µM for mTyr and hTyr, respectively. Verproside showed 5.6-fold higher efficacy than that of its positive control (kojic acid in hTyr). The most potent tyrosinase inhibitor, verproside, features a 3,4-dihydroxybenzoic acid moiety on the iridoid glycoside and inhibits tyrosinase in a time-dependent and competitive manner. Among these three compounds, verproside is bound to the active site pocket with a docking energy of -6.9 kcal/mol and four hydrogen bonding interactions with HIS61 and HIS85.

Oxidoreductase enzymes: Characteristics, applications, and challenges as a biocatalyst

Oxidoreductases are enzymes with distinctive characteristics that favor their use in different areas, such as agriculture, environmental management, medicine, and analytical chemistry. Among these enzymes, oxidases, dehydrogenases, peroxidases, and oxygenases are very interesting. Because their substrate diversity, they can be used in different biocatalytic processes by homogeneous and heterogeneous catalysis. Immobilization of these enzymes has favored their use in the solution of different biotechnological problems, with a notable increase in the study and optimization of this technology in the last years. In this review, the main structural and catalytical features of oxidoreductases, their substrate specificity, immobilization, and usage in biocatalytic processes, such as bioconversion, bioremediation, and biosensors obtainment, are presented.

Tyrosinase enzyme purification and immobilization from Pseudomonas sp. EG22 using cellulose coated magnetic nanoparticles: characterization and application in melanin production

Melanin is a brown-black pigment with significant roles in various biological processes. The tyrosinase enzyme catalyzes the conversion of tyrosine to melanin and has promising uses in the pharmaceutical and biotechnology sectors. This research aims to purify and immobilize the tyrosinase enzyme from Pseudomonas sp. EG22 using cellulose-coated magnetic nanoparticles. Various techniques were utilized to examine the synthesized nanoparticles, which exhibited a spherical shape with an average diameter of 12 nm and a negative surface potential of - 55.7 mV with a polydispersity index (PDI) of 0.260. Comparing the immobilized magnetic tyrosinase enzyme with the free enzyme, the study's findings showed that the immobilized tyrosinase enzyme had optimal activity at a pH of 6 and a temperature of 35 °C, and its activity increased as the concentration of tyrosine increased. The study investigated the antibacterial and anticancer bioactivity of the enzyme's melanin product and found that it exhibited potential antibacterial activity against a multi-drug resistant strain including S. aureus and E. coli. The produced melanin also demonstrated the potential to decrease cell survival and induce apoptosis in initiation cells.

Bacterial Tyrosinase Inhibition, Hemolytic and Thrombolytic Screening, and In Silico Modeling of Rationally Designed Tosyl Piperazine-Engrafted Dithiocarbamate Derivatives

Piperazine is a privileged moiety that is a structural part of many clinical drugs. Piperazine-based scaffolds have attracted the attention of pharmaceutical and medicinal scientists to develop novel, efficient therapeutic agents owing to their significant and promising biological profile. In the current study, an ecofriendly ultrasonic-assisted synthetic approach was applied to achieve a novel series of 1-tosyl piperazine dithiocarbamate acetamide hybrids 4a-4j, which was evaluated for in vitro tyrosinase inhibition and thrombolytic and hemolytic cytotoxic activities. Among all the piperazine-based dithiocarbamate acetamide target molecules 4a-4j, the structural analogs 4d displayed excellent tyrosinase inhibition efficacy (IC50 = 6.88 ± 0.11 µM) which was better than the reference standard drugs kojic acid (30.34 ± 0.75 µM) and ascorbic acid (11.5 ± 1.00 µM), respectively, which was further confirmed by in silico induced-fit docking (IFD) simulation Good tyrosinase activities were exhibited by 4g (IC50 = 7.24 ± 0.15 µM), 4b (IC50 = 8.01 ± 0.11 µM) and 4c (IC50 = 8.1 ± 0.30 µM) dithiocarbamate acetamides, which were also better tyrosinase inhibitors than the reference drugs but were less active than the 4d structural hybrid. All the derivatives are less toxic, having values in the 0.29 ± 0.01% to 15.6 ± 0.5% range. The scaffold 4b demonstrated better hemolytic potential (0.29 ± 0.01%), while a remarkably high thrombolytic chemotherapeutic potential was displayed by analog 4e (67.3 ± 0.2%).

Light effects on Lasiodiplodia theobromae metabolome cultured in vitro

INTRODUCTION

The present work identified and compared intracellular metabolites and metabolic networks in mycelial cultures of Lasiodiplodia theobromae grown under 12 natural light and 24 hours' dark using a 1 H NMR-based metabolomics approach.

MATERIALS AND METHODS

Fungal cultures were grown in potato dextrose media, and metabolites were extracted by sonication with sodium phosphate-buffered saline (pH = 6.0, 10% D2O, 0.1 mM TSP) from mycelium samples collected every week over four weeks.

RESULTS

Multivariate analyses revealed that the light exposure group showed a positive correlation within beta-hydroxybutyrate, acetoacetate, acetone, betaine, choline, glycerol, and phosphocholine. On the other hand, phenyl acetate, leucine, isoleucine, valine, and tyrosine were positively correlated with dark conditions. Light favored the oxidative degradation of valine, leucine, and isoleucine, leading to the accumulation of choline, phosphocholine, betaine, and ketone bodies (ketogenesis). Ketogenesis, gluconeogenesis, and the biosynthesis of choline, phosphocholine, and betaine, were considered discriminatory routes for light conditions. The light-sensing pathways were interlinked with fungal development, as verified by the increased production of mycelia biomass without fruiting bodies and stress signaling, as demonstrated by the increased production of pigments.

Tyrosinase Inhibitors: A Perspective

Due to its integral role in the biosynthesis of melanin in all kingdoms of life, tyrosinase has become an extremely important target for inhibition in several sectors of research including agricultural and cosmetic research. Inhibitors of tyrosinase have made it to the market in the cosmetics industry, but their use has been limited due to conflicting efficacy and potential toxicity, which has led to several small molecules being removed from the market. Undaunted, researchers have continued to pursue tyrosinase inhibitors with varying degrees of success. These pursuits have built an impressive and rich library of research. This review is intended to provide a perspective of the past twenty years (2003-2023) of research on tyrosinase inhibitors by highlighting exemplar molecules and developments.

Tyrosinase Enzyme Purification and Immobilization from Pseudomonas sp. EG22 Using Cellulose Coated Magnetic Nanoparticles: Characterization of Bioactivity in Melanin Product.. [DOI: 10.21203/rs.3.rs-3100351/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Melanin is a brown-black pigment produced by a variety of organisms and has significant roles in various biological processes such as insect cuticle sclerotization, wound healing, and fruit ripening. The tyrosinase enzyme catalyzes the conversion of tyrosine to melanin. Research on this enzyme and its derivatives has revealed promising uses in the pharmaceutical and biotechnology sectors. The aim of this research is to purify and immobilize the tyrosinase enzyme from Pseudomonas sp. EG22 using cellulose-coated magnetic nanoparticles. Various techniques, such as UV-visible spectroscopy, transmission electron microscopy (TEM), Zeta Sizer Nano ZS, and FTIR, were utilized to examine the synthesized nanoparticles. According to the findings, the nanoparticles exhibited a spherical shape with an average diameter of 12 nm. Furthermore, they possessed a negative surface charge, as evidenced by a polydispersity index (PDI) of 0.260 and a surface potential of -55.7 mV. The antibacterial and anticancer bioactivity of the enzyme's melanin product is also investigated. Results of the study indicated optimum tyrosinase activity at pH 6 and 35°C and increased with increasing tyrosine concentration. The results indicate that by immobilizing the tyrosinase enzyme on cellulose coated magnetic nanoparticles, its stability can be improved, enabling longer usage. Moreover, this method could prove beneficial in increasing the production of melanin. Produced melanin showed potential antibacterial activity against multi-drug resistant strain of Citrobacter freundii. The potential of melanin pigment to decrease cell survival and induce apoptosis in initiation cells was demonstrated. When treated with the IC50 concentration, HepG2 cells showed reduced resistance to melanin pigment.

Anti-tyrosinase and antimelanogenic effect of cinnamic acid derivatives from Prunus mahaleb L.: Phenolic composition, isolation, identification and inhibitory activity

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional use of Prunus species against skin diseases and especially for skin lightning cosmeceutical purposes is widespread in many cultures. Prunus mahaleb L. is a well known food plant and used in the baking industry for flavoring. The fruit kernels (endocarp) are used in India for hyperpigmentation.

AIM OF THE STUDY

To investigate the chemical composition with the antimelanogenesis effect of P. mahaleb seed and kernel extracts and isolated compounds.

MATERIALS AND METHODS

Isolation studies performed from the methanol extracts obtained from kernels and structures were determined using NMR and MS analysis. Antimelanogenesis effect was determined by mushroom tyrosinase assay, cellular tyrosinase assay and melanin content assay using B16F10 murine melanoma cells.

RESULTS

Five cinnamic acid derivatives were isolated and their structures (2-O-β-glucopyranosyloxy-4-methoxy-hydrocinnamic acid (1), cis-melilotoside (2), dihydromelilotoside (3), trans-melilotoside (4), 2-O-β-glucosyloxy-4-methoxy trans-cinnamic acid (5)) were elucidated using advanced spectroscopic methods. Mushroom tyrosinase enzyme inhibition of extracts, fractions and pure compounds obtained from P. mahaleb kernels were investigated and structure-activity relationship revealed. According to a detailed, comprehensive and validated LC-MS/MS technique analysis, vanilic acid (41.407 mg/g), protocatechuic acid (8.992 mg/g) and ferulic acid (4.962 mg/g) in the kernel ethylacetate fraction; quinic acid (14.183 mg/g), fumaric acid (8.349 mg/g) and aconitic acid (5.574 mg/g) were found as major phenolic compounds in the water fraction. The correlation of trace element copper content in extracts and fractions with mushroom enzyme activity was determined. By examining the enzyme kinetics of the compounds with effective cinnamic acid derivatives, inhibition types and enzyme binding constants K_i were calculated. Compounds 1,3 and 5 exhibited high noncompetitive tyrosinase inhibitory activity against L-tyrosine substrates, with IC₅₀ values of 0.22, 0.31 and 0.37 mM respectively. In addition compounds 1, 3 and 5 showed dose-dependent inhibitory effects on intracellular tyrosinase and melanin levels in α-melanocyte-stimulating hormone (α-MSH)-induced B16F10 melanoma cells.

CONCLUSIONS

Potent tyrosinase inhibitory compounds and extracts of P. mahaleb kernels suggest that it could be a new, non-toxic and inexpensive resource for the cosmeceutical industry and in skin diseases associated with hyperpigmentation.

Tissue engineering modalities in skeletal muscles: focus on angiogenesis and immunomodulation properties

Muscular diseases and injuries are challenging issues in human medicine, resulting in physical disability. The advent of tissue engineering approaches has paved the way for the restoration and regeneration of injured muscle tissues along with available conventional therapies. Despite recent advances in the fabrication, synthesis, and application of hydrogels in terms of muscle tissue, there is a long way to find appropriate hydrogel types in patients with congenital and/or acquired musculoskeletal injuries. Regarding specific muscular tissue microenvironments, the applied hydrogels should provide a suitable platform for the activation of endogenous reparative mechanisms and concurrently deliver transplanting cells and therapeutics into the injured sites. Here, we aimed to highlight recent advances in muscle tissue engineering with a focus on recent strategies related to the regulation of vascularization and immune system response at the site of injury.

Design, Synthesis, In Vitro, and In Silico Insights of 5-(Substituted benzylidene)-2-phenylthiazol-4(5H)-one Derivatives: A Novel Class of Anti-Melanogenic Compounds

(Z)-5-Benzylidene-2-phenylthiazol-4(5H)-one ((Z)-BPT) derivatives were designed by combining the structural characteristics of two tyrosinase inhibitors. The double-bond geometry of trisubstituted alkenes, (Z)-BPTs 1-14, was determined based on the ³J_C,Hβ coupling constant of ¹H-coupled ¹³C NMR spectra. Three (Z)-BPT derivatives (1-3) showed stronger tyrosinase inhibitory activities than kojic acid; in particular, 2 was to be 189-fold more potent than kojic acid. Kinetic analysis using mushroom tyrosinase indicated that 1 and 2 were competitive inhibitors, whereas 3 was a mixed-type inhibitor. The in silico results revealed that 1-3 could strongly bind to the active sites of mushroom and human tyrosinases, supporting the kinetic results. Derivatives 1 and 2 decreased the intracellular melanin contents in a concentration-dependent manner in B16F10 cells, and their anti-melanogenic efficacy exceeded that of kojic acid. The anti-tyrosinase activity of 1 and 2 in B16F10 cells was similar to their anti-melanogenic effects, suggesting that their anti-melanogenic effects were primarily owing to their anti-tyrosinase activity. Western blotting of B16F10 cells revealed that the derivatives 1 and 2 inhibited tyrosinase expression, which partially contributes to their anti-melanogenic ability. Several derivatives, including 2 and 3, exhibited potent antioxidant activities against ABTS cation radicals, DPPH radicals, ROS, and peroxynitrite. These results suggest that (Z)-BPT derivatives 1 and 2 have promising potential as novel anti-melanogenic agents.

A Comprehensive Review of Food Hydrogels: Principles, Formation Mechanisms, Microstructure, and Its Applications

Food hydrogels are effective materials of great interest to scientists because they are safe and beneficial to the environment. Hydrogels are widely used in the food industry due to their three-dimensional crosslinked networks. They have also attracted a considerable amount of attention because they can be used in many different ways in the food industry, for example, as fat replacers, target delivery vehicles, encapsulating agents, etc. Gels-particularly proteins and polysaccharides-have attracted the attention of food scientists due to their excellent biocompatibility, biodegradability, nutritional properties, and edibility. Thus, this review is focused on the nutritional importance, microstructure, mechanical characteristics, and food hydrogel applications of gels. This review also focuses on the structural configuration of hydrogels, which implies future potential applications in the food industry. The findings of this review confirm the application of different plant- and animal-based polysaccharide and protein sources as gelling agents. Gel network structure is improved by incorporating polysaccharides for encapsulation of bioactive compounds. Different hydrogel-based formulations are widely used for the encapsulation of bioactive compounds, food texture perception, risk monitoring, and food packaging applications.

Screening and Structure-Activity Relationship for Selective and Potent Anti-Melanogenesis Agents Derived from Species of Mulberry (Genus Morus)

Tyrosinase is a multifunctional, copper-containing and rate-limiting oxidase that catalyses crucial steps in the melanogenesis pathway and is responsible for skin-pigmentation abnormalities in mammals. Numerous tyrosinase inhibitors derived from natural and synthetic sources have been identified as an objective for the development of anti-melanogenesis agents. However, due to side effects and lack of expected efficiency, only a small percentage of them are used for medical and cosmetic purposes. This critical review focuses on searching for novel active substances and recently discovered plant-derived anti-tyrosinase inhibitors from the Morus genus (Moraceae family). A detailed analysis of their structure-activity relationships is discussed. The information contained in this article is crucial for the cosmetics and medical industries, in order to show new directions for the effective search for natural anti-melanogenesis products (with satisfactory efficiency and safety) to treat and cure hyperpigmentation.

A comprehensive phytochemical, biological, and toxicological studies of roots and aerial parts of Crotalaria burhia Buch.-Ham: An important medicinal plant

This study was designed to seek the phytochemical analysis, antioxidant, enzyme inhibition, and toxicity potentials of methanol and dichloromethane (DCM) extracts of aerial and root parts of Crotalaria burhia. Total bioactive content, high-performance liquid chromatography-photodiode array detector (HPLC-PDA) polyphenolic quantification, and ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) analysis were utilized to evaluate the phytochemical composition. Antioxidant [including 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH)], 2,2'-azino-bis[3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power assay (FRAP), cupric reducing antioxidant capacity CUPRAC, phosphomolybdenum, and metal chelation assays] and enzyme inhibition [against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-glucosidase, α-amylase, and tyrosinase] assays were carried out for biological evaluation. The cytotoxicity was tested against MCF-7 and MDA-MB-231 breast cell lines. The root-methanol extract contained the highest levels of phenolics (37.69 mg gallic acid equivalent/g extract) and flavonoids (83.0 mg quercetin equivalent/g extract) contents, and was also the most active for DPPH (50.04 mg Trolox equivalent/g extract) and CUPRAC (139.96 mg Trolox equivalent /g extract) antioxidant assays. Likewise, the aerial-methanol extract exhibited maximum activity for ABTS (94.05 mg Trolox equivalent/g extract) and FRAP (64.23 mg Trolox equivalent/g extract) assays. The aerial-DCM extract was noted to be a convincing cholinesterase (AChE; 4.01 and BChE; 4.28 mg galantamine equivalent/g extract), and α-glucosidase inhibitor (1.92 mmol acarbose equivalent/g extract). All of the extracts exhibited weak to modest toxicity against the tested cell lines. A considerable quantities of gallic acid, catechin, 4-OH benzoic acid, syringic acid, vanillic acid, 3-OH-4-MeO benzaldehyde, epicatechin, p-coumaric acid, rutin, naringenin, and carvacrol were quantified via HPLC-PDA analysis. UHPLC-MS analysis of methanolic extracts from roots and aerial parts revealed the tentative identification of important phytoconstituents such as polyphenols, saponins, flavonoids, and glycoside derivatives. To conclude, this plant could be considered a promising source of origin for bioactive compounds with several therapeutic uses.

Use of soil actinomycetes for pharmaceutical, food, agricultural, and environmental purposes

In this article, we reviewed the international scientific production of the last years on actinomycetes isolated from soil aiming to report recent advances in using these microorganisms for different applications. The most promising genera, isolation conditions and procedures, pH, temperature, and NaCl tolerance of these bacteria were reported. Based on the content analysis of the articles, most studies have focused on the isolation and taxonomic description of new species of actinomycetes. Regarding the applications, the antimicrobial potential (antibacterial and antifungal) prevailed among the articles, followed by the production of enzymes (cellulases and chitinases, etc.), agricultural uses (plant growth promotion and phytopathogen control), bioremediation (organic and inorganic contaminants), among others. Furthermore, a wide range of growth capacity was verified, including temperatures from 4 to 60 °C (optimum: 28 °C), pH from 3 to 13 (optimum: 7), and NaCl tolerance up to 32% (optimum: 0-1%), which evidence a great tolerance for actinomycetes cultivation. Streptomyces was the genus with the highest incidence among the soil actinomycetes and the most exploited for different uses. Besides, the interest in isolating actinomycetes from soils in extreme environments (Antarctica and deserts, for example) is growing to explore the adaptive capacities of new strains and the secondary metabolites produced by these microorganisms for different industrial interests, especially for pharmaceutical, food, agricultural, and environmental purposes.

Nomilin from Yuzu Seed Has In Vitro Antioxidant Activity and Downregulates Melanogenesis in B16F10 Melanoma Cells through the PKA/CREB Signaling Pathway

Yuzu (Citrus junos) is a citrus plant native to Asian countries, including Korea, Japan, and China. Yuzu peel and seed contain abundant vitamin C, citric acid, and polyphenols. Although the antioxidative and antimelanogenic activities of other citrus fruits and yuzu extract have been reported, the tyrosinase inhibitory activity of the limonoid aglycone contained in yuzu seed extract is unknown. We separated yuzu seeds into the husk, shell, and meal and evaluated antioxidant activity of each. The limonoid glucoside fraction of the husk identified nomilin, a novel tyrosinase inhibitor. We performed tyrosinase inhibitory activity and noncompetitive inhibition assays and docking studies to determine nomilin binding sites. Furthermore, we evaluated the antioxidative mechanism and antimelanogenic activity of nomilin in B16F10 melanoma cells. The concentration of nomilin that did not show toxicity was <100 µg/mL. Nomilin suppressed protein expression of TYR, TRP-1, TRP-2, and microphthalmia-associated transcription factor (MITF) in a concentration-dependent manner. Nomilin significantly reduced the levels of p-CREB and p-PKA at the protein level and decreased the levels of skin-whitening-related factors MITF, tyrosinase, TRP-1, and TRP-2 at the mRNA level in a concentration-dependent manner. Thus, nomilin from yuzu seed husk can be used as a skin-whitening agent in cosmetics.

Bacterial pigments: A colorful palette reservoir for biotechnological applications

Synthetic derivatives are currently used instead of pigments in many applicative fields, from food to feed, from pharmaceutical to diagnostic, from agronomy to industry. Progress in organic chemistry allowed to obtain rather cheap compounds covering the whole color spectrum. However, several concerns arise from this chemical approach, as it is mainly based on nonrenewable resources such as fossil oil, and the toxicity or carcinogenic properties of products and/or precursors may be harmful for personnel involved in the productive processes. In this scenario, microorganisms and their pigments represent a colorful world to discover and reconsider. Each living bacterial strain may be a source of secondary metabolites with peculiar functions. The aim of this review is to link the physiological role of bacterial pigments with their potential use in different biotechnological fields. This enormous potential supports the big challenge for the development of strategies useful to identify, produce, and purify the right pigment for the desired application. At the end of this ideal journey through the world of bacterial pigments, the attention will be focused on melanin compounds, whose production relies upon different techniques ranging from natural producers, heterologous hosts, or isolated enzymes. In a green workflow, the microorganisms represent the starting and final point of pigment production.

Paving the way towards effective plant-based inhibitors of hyaluronidase and tyrosinase: a critical review on a structure-activity relationship

Human has used plants to treat many civilisation diseases for thousands of years. Examples include reserpine (hypertension therapy), digoxin (myocardial diseases), vinblastine and vincristine (cancers), and opioids (palliative treatment). Plants are a rich source of natural metabolites with multiple biological activities, and the use of modern approaches and tools allowed finally for more effective bioprospecting. The new phytochemicals are hyaluronidase (Hyal) inhibitors, which could serve as anti-cancer drugs, male contraceptives, and an antidote against venoms. In turn, tyrosinase inhibitors can be used in cosmetics/pharmaceuticals as whitening agents and to treat skin pigmentation disorders. However, the activity of these inhibitors is stricte dependent on their structure and the presence of the chemical groups, e.g. carbonyl or hydroxyl. This review aims to provide comprehensive and in-depth evidence related to the anti-tyrosinase and anti-Hyal activity of phytochemicals as well as confirming their efficiency and future perspectives.

The Structure of Bilirubin Oxidase from Bacillus pumilus Reveals a Unique Disulfide Bond for Site-Specific Direct Electron Transfer

Efficient oxygen-reducing biocatalysts are essential for the development of biofuel cells or photo-bioelectrochemical applications. Bilirubin oxidase (BOD) is a promising biocatalyst for oxygen reduction processes at neutral pH and low overpotentials. BOD has been extensively investigated over the last few decades. While the enzyme’s internal electron transfer process and methods to establish electrical communication with electrodes have been elucidated, a crystal structure of BOD from bacterial origin has never been determined. Here we present the first crystal structure of BOD from Bacillus pumilus (BpBOD) at 3.5 Å resolution. Overall, BpBOD shows high homology with the fungal enzymes; however, it holds a unique surface-exposed disulfide bond between Cys229 and Cys322 residues. We present methodologies to orient the T1 site towards the electrode by coupling the reduced disulfide bond with maleimide moiety on the electrodes. The developed configurations were further investigated and revealed improved direct electron transfer rates with the electrodes. The work presented here may contribute to the construction of rationally designed bioanodes or biocathode configurations that are based on redox-active enzymes.

Metabolomics and transcriptomics unravel the mechanism of browning resistance in Agaricus bisporus

Agaricus bisporus is widely consumed on the world market. The easy browning of mushroom surface is one of the most intuitive factors affecting consumer purchase. A certain cognition on browning mechanism has been made after years of research. At present, people slow down the browning of mushrooms mainly by improving preservation methods. In addition, breeding is also a reliable way. In the production practice, we have identified some browning-resistant varieties, and we selected a browning-resistant variety to compare with an ordinary variety to reveal the resistance mechanism. Using transcriptomics and metabolomics, the differences in gene expression and metabolite levels were revealed, respectively. The results showed that differentially expressed genes (DEGs) like AbPPO4, AbPPO3 and AbPPO2 were differently expressed and these DEGs were involved in many pathways related to browning. The expression of AbPPO expression play an important role in the browning of A. bisporus and multiple PPO family members are involved in the regulation of browning. However, the resistance to browning cannot be judged only by the expression level of AbPPOs. For metabolomics, most of the different metabolites were organic acids. These organic acids had a higher level in anti-browning (BT) than easy-browning varieties (BS), although the profile was very heterogeneous. On the contrary, the content of trehalose in BS was significantly higher than that in BT. Higher organic acids decreased pH and further inhibited PPO activity. In addition, the BS had a higher content of trehalose, which might play roles in maintaining PPO activity. The difference of browning resistance between BS and BT is mainly due to the differential regulation mechanism of PPO.

Endophytic fungi: a potential source of industrial enzyme producers

Microbial enzymes have gained interest for their widespread use in various industries and medicine due to their stability, ease of production, and optimization. Endophytic fungi in plant tissues produce a wide range of secondary metabolites and enzymes, which exhibit a variety of biological activities. The present review illustrates promising applications of enzymes produced by endophytic fungi and discusses the characteristic features of the enzymes, application of the endophytic fungal enzymes in therapeutics, agriculture, food, and biofuel industries. Endophytic fungi producing ligninolytic enzymes have possible biotechnological applications in lignocellulosic biorefineries. The global market of industrially important enzymes, challenges, and future prospects are illustrated. However, the commercialization of endophytic fungal enzymes for industrial purposes is yet to be explored. The present review suggests that endophytic fungi can produce various enzymes and may become a novel source for upscaling the production of enzymes of industrial use.

Comparative analysis of mussel foot protein 3B co-expressed with tyrosinases provides a potential adhesive biomaterial

Mussel foot proteins (Mfps), which help mussels attach to various surfaces, are considered to be promising biomaterials due to their outstanding adhesive properties. However, limited production and lack of post-translational modifications of tyrosine residues into 3,4-dihydroxyphenylalanine (Dopa) in bacterial expression systems have hampered their applications. In the present study, for the first time we established the expression of recombinant Mytilus galloprovincialis foot protein type 3 variant B (fp-3B) in Escherichia coli; and achieved its viable production (~51 mg/L). Additionally, the Dopa content and adhesive properties of fp-3B co-expressed using various types of tyrosinases were compared. Consequently, the co-expression of fp-3B construct together with tyrosinase from Verrucomicrobium spinosum (TyrVs) yielded up to 87 mg/L of modified fp-3B; hydroxylation of tyrosine residues accounted for 57.18% by acid-borate difference spectroscopy. The modified fp-3B also showed significant coating and adhesive ability, and its bulk-scale adhesive strength was 2.9-fold higher than that of unmodified fp-3B. Compared with other type 3 mussel foot proteins, the high-yield expression and extensive hydroxylation level of the recombinant protein indicate that fp-3B co-expressed with TyrVs (3B-Vs) has the potential to be widely used as bioglues.

Melanin production by Pseudomonas sp. and in silico comparative analysis of tyrosinase gene sequences

Background

Melanin finds enormous applications in different industries for its unique photoprotective and anti-oxidant properties. Due to its emerging demand, scientific researchers are putting efforts to unravel more microorganisms with a potential of producing melanin on large scale. Hence, the present study was aimed at the isolation of extracellular melanin producing microorganisms from lime quarries of Karnataka, India. Besides this, the tyrosinase gene governing melanin synthesis in different organisms were compared in silico to understand its evolutionary aspects.

Material and methods

Melanin producing microorganisms were screened on tyrosine gelatin beef extract agar medium. Potential isolate was explored for submerged production of melanin in broth containing L-tyrosine. Melanin was characterized by UV-Vis spectroscopy, thin layer and high performance liquid chromatographic techniques. Antibacterial activity of melanin was performed by agar well assay. Comparative tyrosinase gene sequence analysis was performed by using Geneious 2021.1 trial version software.

Results

Pseudomonas otitidis DDB2 was found to be potential for melanin production. No antibacterial activity was exerted by the melanin against tested pathogens. The in silico studies showed that the common central domain of tyrosinase protein sequence of selected Pseudomonas sps. exhibited 100% identity with the common central domain of Homo sapiens tyrosinase (NP_000363.1).

Conclusions

Our study shows the production of melanin in good quantities by the isolate Pseudomonas otitidis DDB2 which can be explored for scale-up process. Since the melanin formed is of eumelanin type and the tyrosinase gene sequence of several Pseudomonas sp. showed relatedness to humans, this molecule may be further developed for sunscreen formulations.

Unleashing the shape of L-DOPA at last

Herein, we report the first rotational study of neutral L-DOPA, an extensively used supramolecular synthon and an amino acid precursor of the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) using broadband and narrowband Fourier transform microwave spectroscopies coupled with a laser ablation vaporization system. The spectroscopic parameters derived from the analysis of the rotational spectrum conclusively identify the existence of four distinct conformers of L-DOPA in the supersonic jet, further rejecting the previously reported catechol ring-induced conformational restriction. The analysis of the ¹⁴N nuclear quadrupole coupling hyperfine structure further revealed the orientation of the N-bearing functional group, proving the existence of stabilizing N-H⋯π interactions for the observed structures.

Application of bacterial tyrosinases in organic synthesis

Bacterial tyrosinases, as in the case of other bacterial oxidative enzymes, have been found to possess biochemical characteristics that typically make them more suited to applications requiring special operational conditions such as alkaline pH, high or low temperature, the presence of organic solvents, and the presence of inhibitors. Even though a great deal is known about fungal tyrosinases, bacterial tyrosinases still vastly remain underexplored for their potential application in organic synthesis. A literature survey in particular highlights the gaps in our knowledge pertaining to their biochemical properties. Bacterial tyrosinases have not only shown promise in the synthesis of medically important compounds such as L-3,4-dihydroxyphenylalanine (L-DOPA) and melanin but have also seen application in cross-linking reactions of proteins and the polymerization of environmental pollutants. Their ability to catalyse o-hydroxylation reactions have shown some degree of promise in the biocatalytic conversion of resveratrol to piceatannol, tyrosol to hydroxytyrosol, and many more. In this review, we will explore the world of bacterial tyrosinases, their current applications, and future perspectives for the application of these enzymes in organic synthesis.

Engineering Wired Life: Synthetic Biology for Electroactive Bacteria

Electroactive bacteria produce or consume electrical current by moving electrons to and from extracellular acceptors and donors. This specialized process, known as extracellular electron transfer, relies on pathways composed of redox active proteins and biomolecules and has enabled technologies ranging from harvesting energy on the sea floor, to chemical sensing, to carbon capture. Harnessing and controlling extracellular electron transfer pathways using bioengineering and synthetic biology promises to heighten the limits of established technologies and open doors to new possibilities. In this review, we provide an overview of recent advancements in genetic tools for manipulating native electroactive bacteria to control extracellular electron transfer. After reviewing electron transfer pathways in natively electroactive organisms, we examine lessons learned from the introduction of extracellular electron transfer pathways into Escherichia coli. We conclude by presenting challenges to future efforts and give examples of opportunities to bioengineer microbes for electrochemical applications.

Tyrosinase-based production of L-DOPA by Corynebacterium glutamicum

An increase in the number of elderly people suffering from the symptoms of Parkinson's disease is leading to an expansion in the market size of 3,4-dihydroxyphenyl-L-alanine (L-DOPA), which is the most commonly used drug for the treatment of this disease. Need for better quality products through economically feasible and sustainable processes makes biotechnological approaches attractive. The current study is focused on heterologous expression of Ralstonia solanacearum tyrosinase in Corynebacterium glutamicum cells to produce L-DOPA during growth on glucose or glucose/xylose mixtures. Whole-cells pre-grown on glucose were further exploited for biotransformation of L-tyrosine to L-DOPA. To prevent L-DOPA oxidation, not only the most commonly used agent, ascorbic acid, but also for the first time, thymol was evaluated. The highest L-DOPA titer was 0.26 ± 0.02 g/L at the end of growth on a mixture of 1% xylose and 3% glucose in the presence of 200 μM thymol as the oxidation inhibitor. The ability to co-utilize glucose and xylose to reach this titer could make these cells ideal for L-DOPA production using hydrolyzed lignocellulosic biomass. When the pre-grown cells were further used for biotransformation, the highest L-DOPA yield was 0.61 ± 0.02 g/gDCW with 4 mM ascorbic acid. Since L-tyrosine biotransformation is primarily dependent on tyrosinase activity, yield in this route could be improved by optimizing reaction conditions. As the industrial workhorse for amino acid production, these C. glutamicum cells will clearly benefit from strain development efforts and bioprocess optimization towards sustainable and economically feasible L-DOPA production. KEY POINTS: • Fermentative l-DOPA production was achieved in C. glutamicum. • Tyrosinase produced by C. glutamicum cells successfully transformed l-Tyr. • Thymol proved to be a significant oxidation inhibitor for l-DOPA production.

Recent advance in the discovery of tyrosinase inhibitors from natural sources via separation methods

Tyrosinase (TYR) inhibitors are in great demand in the food, cosmetic and medical industrials due to their important roles. Therefore, the discovery of high-quality TYR inhibitors is always pursued. Natural products as one of the most important sources of bioactive compounds discovery have been increasingly used for TYR inhibitors screening. However, due to their complex compositions, it is still a great challenge to rapid screening and identification of biologically active components from them. In recent years, with the help of separation technologies and the affinity and intrinsic activity of target enzymes, two advanced approaches including affinity screening and inhibition profiling showed great promises for a successful screening of bioactive compounds from natural sources. This review summarises the recent progress of separation-based methods for TYR inhibitors screening, with an emphasis on the principle, application, advantage, and drawback of each method along with perspectives in the future development of these screening techniques and screened hit compounds.

Potential opportunities of thinned clusters in viticulture: a mini review

Crop thinning is a common practice performed in the vineyard consisting of whole clusters or individual fruits being removed after flowering is attained. Current studies have reported that unripe grape products as verjuice and sour grape sauce contain high content of bioactive compounds such as polyphenols, sugars, organic acids, nitrogenous compounds and sterols. This mini-review overviewed the bioactive components obtained from thinned unripe grapes such as phenolic compounds, sugars, organic acids, minerals, nitrogen compounds and sterols, and their use as antibrowning and whitening agents, natural catalysts, food preservative and food additive. In addition, their beneficial effects for human health also were reviewed, as well as the practices to maximize the extraction of antioxidant compounds. Therefore, revalorizing the waste from this management practice in viticulture can increase the vineyard sustainability and farmers' economic profits. © 2021 Society of Chemical Industry.

Engineered tyrosinases with broadened bio-catalysis scope: immobilization using nanocarriers and applications

Enzyme immobilization is a widely used technology for creating more stable, active, and reusable biocatalysts. The immobilization process also improves the enzyme's operating efficiency in industrial applications. Various support matrices have been designed and developed to enhance the biocatalytic efficiency of immobilized enzymes. Given their unique physicochemical attributes, including substantial surface area, rigidity, semi-conductivity, high enzyme loading, hyper catalytic activity, and size-assisted optical properties, nanomaterials have emerged as fascinating matrices for enzyme immobilization. Tyrosinase is a copper-containing monooxygenase that catalyzes the o-hydroxylation of monophenols to catechols and o-quinones. This enzyme possesses a wide range of uses in the medical, biotechnological, and food sectors. This article summarizes an array of nanostructured materials as carrier matrices for tyrosinase immobilization. Following a detailed background overview, various nanomaterials, as immobilization support matrices, including carbon nanotubes (CNTs), carbon dots (CDs), carbon black (CB), nanofibers, Graphene nanocomposite, platinum nanoparticles, nano-sized magnetic particles, lignin nanoparticles, layered double hydroxide (LDH) nanomaterials, gold nanoparticles (AuNPs), and zinc oxide nanoparticles have been discussed. Next, applied perspectives have been spotlights with particular reference to environmental pollutant sensing, phenolic compounds detection, pharmaceutical, and food industry (e.g., cereal processing, dairy processing, and meat processing), along with other miscellaneous applications.

Tyrosinase and laccase-producing Bacillus aryabhattai TFG5 and its role in the polymerization of phenols

BACKGROUND

Tyrosinases and laccases are oxidoreductase enzymes that are used widely in the food, feed, textile, and biofuel industries. The rapidly growing industrial demand for bacterial oxido-reductases has encouraged research on this enzyme worldwide. These enzymes also play a key role in the formation of humic substances (HS) that are involved in controlling the biogeochemical carbon cycle, providing nutrients and bio-stimulants for plant growth, and interacting with inorganic and organic pollutants besides increasing carbon sequestration and mitigating greenhouse gas emission in the environment. The present study aimed to screen and characterize extracellular tyrosinase and laccase-producing soil bacteria that could be utilized in the polymerization of phenols.

RESULTS

Twenty isolates from different soil samples collected from forest ecosystems were characterized through ARDRA using restriction digestion with AluI, HpaII, and HaeIII restriction enzymes. The results of Hierarchical Cluster Analysis (HCA) revealed a 60 % similarity coefficient among 13 out of 20 isolates, of which, the isolate TFG5 exhibited only 10 % similarity when compared to all the other isolates. The isolate TFG5 exhibited both tyrosinase (1.34 U.mL- 1) and laccase (2.01 U.mL- 1) activity and was identified as Bacillus aryabhattai. The increased polymerization activity was observed when B. aryabhattai TFG5 was treated with phenols. The monomers such as catechol, p-Hydroxy benzoic acid, ferulic acid, and salicylic acid were polymerized efficiently, as evidenced by their FT-IR spectra depicting increased functional groups compared to the standard mushroom tyrosinase.

CONCLUSIONS

The polymerization ability of B. aryabhattai TFG5 could be applied to phenol-rich wastewater treatment for efficient precipitation of phenols. Furthermore, tyrosinases can be used for enhancing the synthesis of HS in soil.

Biomorphic Ceramics: Synthesis and Characterization of Preceramic Polymer-Modified Melanin

Recent efforts have demonstrated that the morphology of ceramics can be manipulated to control both their deformation mechanism and mechanical performance. However, precise control of the ceramic nanostructure is still difficult to achieve. Biotemplating, leading to biomorphic materials, provides a facile route to manipulate the nanostructure of the resulting materials, and the use of melanin as a coating provides a new route to biotemplated materials. Melanin is underutilized for structural materials partly due to the cost of procuring it from natural sources and the inability to control the shape and sizes of melanin particles. Taking a combined synthetic biology and chemical synthesis approach, we report the melanization of Escherichia coli and its subsequent silanization and functionalization with preceramic polymers to make novel biomorphic silicon-based ceramic materials. Graft-to and graft-from reactions were used to append preceramic polymers to the melanin, followed by pyrolysis under argon. Samples were analyzed by FTIR, XRD, XPS, and TEM and found to retain the shape and size of the original cells with high fidelity. The homogeneity of coverage and yield of the resulting ceramic materials depended on the type of grafting reaction. This work provides a promising proof-of-concept that bacterial-templated ceramics can be readily made and opens a host of possibilities for further studies and applications.

New tyrosinases with putative action against contaminants of emerging concern

Tyrosinases (EC 1.14.18.1) are type-3 copper metalloenzymes with strong oxidative capacities and low allosteric selectivity to phenolic and non-phenolic aromatic compounds, which have been used as biosensors and biocatalysts to mitigate the impacts of environmental contaminants over aquatic ecosystems. However, the widespread use of these polyphenol oxidases is limited by elevated production costs and restricted knowledge on their spectrum of action. Here, six tyrosinase homologs were identified and characterized from the genomes of four widespread freshwater ciliates using bioinformatics. Next, we performed a virtual screening to calculate binding energies between 3D models of these homologs and ~ 1000 contaminants of emerging concern (CECs), as an indirect approach to identify likely and unlikely targets for tyrosinases. Many fine chemicals, pharmaceuticals, personal care products, illicit drugs, natural toxins, and pesticides exhibited strong binding energies to these new tyrosinases, suggesting the spectrum of targets of these enzymes might be considerably broader than previously thought. Many ciliates, including those carrying tyrosinase genes, are fast-growing unicellular microeukaryotes that can be efficiently cultured, at large scales, under in vitro conditions, suggesting these organisms should be regarded as potential low-cost sources of new environmental biotechnological molecules.

Functionality study of chalcone-hydroxypyridinone hybrids as tyrosinase inhibitors and influence on anti-tyrosinase activity

In an attempt to synthesise new tyrosinase inhibitors, we designed and synthesised a series of chalcone-hydroxypyridinone hybrids as potential tyrosinase inhibitors adopting strategic modifications of kojic acid. All the newly synthesised compounds were characterised by NMR and mass spectrometry. Initial screening of the target compounds demonstrated that compounds 1a, 1d, and 1n had relatively strong inhibitory activities against tyrosinase monophenolase, with IC₅₀ values of 3.07 ± 0.85, 2.25 ± 0.8 and 2.75 ± 1.19 μM, respectively. The inhibitory activity against monophenolase was 6- to 8-fold higher than that of kojic acid. Compounds 1a, 1d, and 1n also showed inhibition of diphenolase, with IC₅₀ values of 17.05 ± 0.07, 11.70 ± 0.03 and 19.3 ± 0.28 μM, respectively. The inhibition kinetics of diphenolase indicates that compounds 1a and 1d induce reversible inhibition on tyrosinase. Finally, we found that copper coordination should be one of the important inhibitory mechanism of these compounds in tyrosinase.

A comprehensive review of the therapeutic potential of α-arbutin

Cosmetic dermatology preparations such as bleaching agents are ingredients with skin-related biological activities for increasing and improving skin beauty. The possibility of controlling skin hyperpigmentation disorders is one of the most important research goals in cosmetic preparations. Recently, cosmetics containing herbal and botanical ingredients have attracted many interests for consumers of cosmetic products because these preparations are found safer than other preparations with synthetic components. However, high-quality trial studies in larger samples are needed to confirm safety and clinical efficacy of phytotherapeutic agents with high therapeutic index. Arbutin (p-hydroxyphenyl-β-d-glucopyranoside) is a bioactive hydrophilic polyphenol with two isomers including alpha-arbutin (4-hydroxyphenyl-α-glucopyranoside) and β-arbutin (4-hydroxyphenyl-β-glucopyranoside). It is used as a medicinal plant in phytopharmacy. Studies have shown that alpha-arbutin is 10 times more effective than natural arbutin. A comparison of IC50 values showed that α-arbutin (with concentration 2.0 mM) has a more potent inhibitory activity on human tyrosinase against natural arbutin (with higher concentration than 30 mM). A review of recent studies showed that arbutin could be beneficial in treatment of various diseases such as hyperpigmentation disorders, types of cancers, central nervous system disorders, osteoporosis, diabetes, etc. This study was designed to describe the therapeutic efficiencies of arbutin.

Biochemical Properties of Tyrosinase from Aspergillus terreus and Penicillium copticola; Undecanoic Acid from Aspergillus flavus, an Endophyte of Moringa oleifera, Is a Novel Potent Tyrosinase Inhibitor

Tyrosinase is a copper-containing monooxygenase catalyzing the O-hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine then to dopaquinone that is profoundly involved in melanin synthesis in eukaryotes. Overactivation of tyrosinase is correlated with hyperpigmentation that is metabolically correlated with severe pathological disorders, so, inhibition of this enzyme is the most effective approach in controlling the overproduction of melanin and its hazardous effects. Thus, searching for a powerful, selective inhibitor of human tyrosinase to limit the hyper-synthesis of melanin is a challenge. Unlike the difficulty of overexpression of human tyrosinase, using fungal tyrosinase as a model enzyme to the human one to evaluate the mechanistics of enzyme inhibition in response to various compounds is the most feasible strategy. Thus, the purification of highly catalytic-efficient fungal tyrosinase, exploring a novel inhibitor, and evaluating the mechanistics of enzyme inhibition are the main objectives of this work. Aspergillus terreus and Penicillium copticola were reported as the most potential tyrosinase producers. The biochemical properties suggest that this enzyme displays a higher structural and catalytic proximity to human tyrosinase. Upon nutritional bioprocessing by Plackett–Burman design, the yield of tyrosinase was increased by about 7.5-folds, compared to the control. The purified tyrosinase was strongly inhibited by kojic acid and A. flavus DCM extracts with IC₅₀ values of 15.1 and 12.6 µg/mL, respectively. From the spectroscopic analysis, the main anti-tyrosinase compounds of A. flavus extract was resolved, and verified as undecanoic acid. Further studies are ongoing to unravel the in vivo effect and cytotoxicity of this compound in fungi and human, that could be a novel drug to various diseases associated with hyperpigmentation by melanin.

Skin-Whitening and Anti-Wrinkle Effects of Bioactive Compounds Isolated from Peanut Shell Using Ultrasound-Assisted Extraction

Response surface methodology was employed to optimize the ultrasound-assisted extraction (UAE) conditions for simultaneous optimization of dependent variables, including DPPH radical scavenging activity (RSA), tyrosinase activity inhibition (TAI), and collagenase activity inhibition (CAI) of peanut shell extracts. The effects of the main variables including extraction time (5.0~55.0 min, X₁), extraction temperature (26.0~94.0 °C, X₂), and ethanol concentration (0.0%~99.5%, X₃) were optimized. Based on experimental values from each condition, quadratic regression models were derived for the prediction of optimum conditions. The coefficient of determination (R²) of the independent variable was in the range of 0.89~0.96, which demonstrates that the regression model is suitable for the prediction. In predicting optimal UAE conditions based on the superimposing method, extraction time of 31.2 min, extraction temperature of 36.6 °C, and ethanol concentration of 93.2% were identified. Under these conditions, RSA of 74.9%, TAI of 50.6%, and CAI of 86.8% were predicted, showing good agreement with the experimental values. A reverse transcription polymerase chain reaction showed that peanut shell extract decreased mRNA levels of tyrosinase-related protein-1 and matrix metalloproteinase-3 genes in B16-F0 cell. Therefore, we identified the skin-whitening and anti-wrinkle effects of peanut shell extracts at protein as well as gene expression levels, and the results show that peanut shell is an effective cosmetic material for skin-whitening and anti-wrinkle effects. Based on this study, peanut shell, which was considered a byproduct, can be used for the development of healthy foods, medicines, and cosmetics.

Enhancing Catecholase Activity of a Recombinant Human Tyrosinase Through Multiple Strategies

Background:

Tyrosinases are copper-containing enzymes that initiate the melanin synthesis. They catalyze the direct oxidation of L-tyrosine or L-DOPA into L-DOPAquinone.

Objectives:

In present study, we aimed to obtain a recombinant tyrosinase with enhanced catecholase activity through site-directed mutagenesis.

Materials and Methods:

The coding sequence of human tyrosinase along with native signal sequence was cloned into pET-28a (+). BL-21 was used as expression host and recombinant protein was purified by Ni-NTA resins. Site-directed mutagenesis was performed on M374 residue to achieve four mutants: M374D, M374T, M374K and M374R. Chloride ions (Cl^-) were removed from all solutions, and an extra amount of Cu²⁺ ions was added to recombinant tyrosinases by a novel technique during the purification process. Removal of Cl^- ions and addition of extra Cu²⁺ ions tripled catecholase activity of the recombinant protein. Therefore, all mutants were obtained under similar conditions.

Results:

Although all the mutants presented higher catecholase activity in comparison to the wild-type enzyme, a significant increase in catecholase activity of the M374D mutant was observed ‒ 13.2-fold. In silico modeling suggested that a de novo hydrogen bond occurs between side chain carboxyl oxygens of D374 and H367 in M374D. In the wild-type tyrosinase, the peptide oxygen atom of M374 is responsible for hydrogen bonding with H367.

Conclusions:

Our data suggests that M374D mutational variant has applications in different areas such as agriculture, industry, and medicine.

The Potential of Selected Agri-Food Loss and Waste to Contribute to a Circular Economy: Applications in the Food, Cosmetic and Pharmaceutical Industries

The food sector includes several large industries such as canned food, pasta, flour, frozen products, and beverages. Those industries transform agricultural raw materials into added-value products. The fruit and vegetable industry is the largest and fastest-growing segment of the world agricultural production market, which commercialize various products such as juices, jams, and dehydrated products, followed by the cereal industry products such as chocolate, beer, and vegetable oils are produced. Similarly, the root and tuber industry produces flours and starches essential for the daily diet due to their high carbohydrate content. However, the processing of these foods generates a large amount of waste several times improperly disposed of in landfills. Due to the increase in the world’s population, the indiscriminate use of natural resources generates waste and food supply limitations due to the scarcity of resources, increasing hunger worldwide. The circular economy offers various tools for raising awareness for the recovery of waste, one of the best alternatives to mitigate the excessive consumption of raw materials and reduce waste. The loss and waste of food as a raw material offers bioactive compounds, enzymes, and nutrients that add value to the food cosmetic and pharmaceutical industries. This paper systematically reviewed literature with different food loss and waste by-products as animal feed, cosmetic, and pharmaceutical products that strongly contribute to the paradigm shift to a circular economy. Additionally, this review compiles studies related to the integral recovery of by-products from the processing of fruits, vegetables, tubers, cereals, and legumes from the food industry, with the potential in SARS-CoV-2 disease and bacterial diseases treatment.

Reductase-catalyzed tetrahydrobiopterin regeneration alleviates the anti-competitive inhibition of tyrosine hydroxylation by 7,8-dihydrobiopterin

l-Tyrosine hydroxylation by tyrosine hydroxylase is a significant reaction for preparing many nutraceutical and pharmaceutical chemicals.

Adsorbed hollow fiber immobilized tyrosinase for the screening of enzyme inhibitors from Pueraria lobata extract

In this study, a method based on adsorbed hollow fiber immobilized tyrosinase (TYR) was developed to screening potential TYR inhibitors from Pueraria lobate extract. Kojic acid and ranitidine were used as positive and negative control to verify the reliability of the proposed method, respectively. Several significant parameters of the screening process, including the amount of P. lobata extract, adsorption time and incubation time, were optimized. After investigating the repeatability of the developed method, seven potential active compounds in P. lobata extract were successfully detected and their chemical structures were tentatively identified by liquid chromatography - mass spectrometry analysis. Furthermore, the inhibitory activity of four identified compounds on TYR was tested in vitro, and three of them, namely, puerarin, puerarin-6″-O-xyloside and puerarin apioside were verified to have good TYR inhibitory activity with IC₅₀ value of 478.5, 513.8, and 877.3 μM, respectively. In addition, the molecular docking results indicated that these compounds could bind to the amino acid residues in TYR catalytic pocket. These results proved that the proposed method is a feasible approach for screening of TYR inhibitors from plant extract.