The light subunit of mushroom Agaricus bisporus tyrosinase: Its biological characteristics and implications

The mannose-binding protein from Agaricus bisporus inhibits the growth of MDA-MB-231 spheroids

A mannose-binding protein from the mushroom Agaricus bisporus (Abmb) inhibits the growth of MDA-MB-231 cells, which is of an aggressive breast cancer subtype. This ability was observed in a monolayer cell (2D) culture setup, which often is unable to capture changes in cell morphology, polarity and division. That shortcoming may overestimate Abmb potency for its development as a pharmaceutical agent and its use in a therapy. Hence, Abmb's inhibition to the cell growth was performed in the 3D cell (spheroid) culture, which is more representative to the situation in vivo. The result showed that, although the presence of Abmb at ~14.7 μM already disrupted the MDA-MB-231 cell morphology in the 2D culture, its presence at ~16.5 μM only ceased the growth of the MDA-MB-231 spheroid. Further, Abmb is unique because structurally it belongs to the R-type lectin (RTL) family; most of mannose-binding protein is of the C-type lectin (CTL). As the natural ligand of Abmb is unknown thus the mechanism of action is unclear, Abmb effect on the cancer cells was assessed via observation of the altered expression of genes involved in the Wnt/β-catenin signalling, which is one of the canonical pathways in the proliferation of cancer cells. The results suggested that Abmb did not alter the pathway upon exerting its anti-proliferative activity to the MDA-MB-231 cells.

Computer-Aided Virtual Screening and In Vitro Validation of Biomimetic Tyrosinase Inhibitory Peptides from Abalone Peptidome

Hyperpigmentation is a medical and cosmetic problem caused by an excess accumulation of melanin or the overexpression of the enzyme tyrosinase, leading to several skin disorders, i.e., freckles, melasma, and skin cancer. Tyrosinase is a key enzyme in melanogenesis and thus a target for reducing melanin production. Although abalone is a good source of bioactive peptides that have been used for several properties including depigmentation, the available information on the anti-tyrosinase property of abalone peptides remains insufficient. This study investigated the anti-tyrosinase properties of Haliotis diversicolor tyrosinase inhibitory peptides (hdTIPs) based on mushroom tyrosinase, cellular tyrosinase, and melanin content assays. The binding conformation between peptides and tyrosinase was also examined by molecular docking and dynamics study. KNN1 showed a high potent inhibitory effect on mushroom tyrosinase with an IC₅₀ of 70.83 μM. Moreover, our selected hdTIPs could inhibit melanin production through the reductions in tyrosinase activity and reactive oxygen species (ROS) levels by enhancing the antioxidative enzymes. RF1 showed the highest activity on both cellular tyrosinase inhibition and ROS reduction. leading to the lower melanin content in B16F10 murine melanoma cells. Accordingly, it can be assumed that our selected peptides exhibited high potential in medical cosmetology applications.

In Vitro Antiviral Activity of Tyrosinase from Mushroom Agaricus bisporus against Hepatitis C Virus

Tyrosinases from a commercial Agaricus bisporus protein extract and directly isolated from white mushrooms were purified in order to obtaining the well-known tyrosinase from A. bisporus (TyrAB) of 45 kDa and a newly discovered 50 kDa tyrosinase isoform (Tyr50 kDa), and tested showing high antiviral activity against the hepatitis C virus for the first time. Cell toxicity and antiviral activity of tyrosinases were determined in cultured Huh 5-2 liver tumor cells transfected with a replicon system (a plasmid that includes all non-structural hepatitis C virus proteins and replicates autonomously). TyrAB was able to inhibit the replication of the hepatitis C virus without inducing toxicity in liver cells. In addition, the post-translational isoform Tyr50 kDa showed higher antiviral capacity than the former (up to 10 times greater), also exhibiting 10 times higher activity than the commercial drug Ribavirin^®. This antiviral activity was directly proportional to the enzymatic activity of tyrosinases, as no antiviral capacity was observed in the inactive form of the enzymes. The tyrosinases approach could represent a new antiviral inhibition mechanism, through a plausible catalytic mechanism of selective hydroxylation of the key role of tyrosine residues in viral proteases.

Prediction of the Mannose-Binding Site in the Agaricus bisporus Mannose-Binding Protein

Agaricus bisporus mannose-binding protein (Abmb) was discovered as part of mushroom tyrosinase (PPO3) complex. Apart from its presence, nothing is known about its function or activity in the mushroom. The protein is evolutionarily related to lectins with β-trefoil fold, which are glucose or galactose (and their derivatives) binding proteins. Abmb is also recently showed to display the typical agglutination activity of lectin when in complex with PPO3; this further supports Abmb similarity to its structural homologs from lectin with β-trefoil fold. However, Abmb has no affinity towards glucose or galactose but for mannose, thus its binding to the sugar may be different from its homologs. To date, the natural ligand of Abmb is unknown and the structure of Abmb in the presence of a ligand is not available. Therefore, the mannose-binding site of Abmb was predicted using molecular docking, which was consulted with the information from its structural homologs. This conservative approach would prevent over-speculation. The mannose-binding site of Abmb is likely located in the same region to that of Abmb structural homologs but with a shift in position due to the presence of additional surface loop. In addition, benefiting from the information from an in vitro study on Abmb sugar specificity, the mannose poses suggested that the sugar might interact with the side chains of Arg15, Thr45, Gln48, Asp49, Asp51 and Arg51. Most of these residues were equally present in Abmb structural homologs despite variation of their positions in the amino acid sequence. The variation probably originates from alteration of its amino acid sequence during evolution.

Immobilization of PR4A3 enzyme in pluronic F127 polymeric micelles against colorectal adenocarcinoma cells and increase of in vitro bioavailability

Traditional therapy for malignant neoplasms involving surgical procedures, radiotherapy and chemotherapy aims to kill neoplastic cells, but also affects normal cells. Therefore, exogenous proteases are the target of studies in cancer therapy, as they have been shown to be effective in suppressing tumors and reducing metastases. Pluronic F127 (F127) is a copolymer of amphiphilic blocks that has shown significant potential for drug administration, as it is capable of incorporating hydrophobic drugs and self-assembling in micrometers of nanometric size. This study investigated the effects of immobilization of the alkaline protease PR4A3 with pluronic F127 micelles on the enzyme-induced cytotoxicity. Protease immobilization was demonstrated through UV-visible and circular dichroism (CD) spectroscopies, as the enzyme interacts with the polymeric micelle of Pluronic F127 without changing its secondary structure. In addition, the immobilized form of the enzyme showed greater bioavailability after passing through the simulated gastrointestinal transit. Cell viability was assessed using the tetrazoic methylthiazole (MTT) assay. The results open perspectives for new research and development for PR4A3 in the treatment of colorectal carcinoma.

Lectins from the Edible Mushroom Agaricus bisporus and Their Therapeutic Potentials

The mushroom Agaricus bisporus secretes biologically active compounds and proteins with benefits for human health. Most reported proteins from A. bisporus are tyrosinases and lectins. Lectins are of therapeutic or pharmaceutical interest. To date, only limited information is available on A. bisporus lectins and lectin-like proteins. No therapeutic products derived from A. bisporus lectin (ABL) are available on the market despite its extensive exploration. Recently, A. bisporus mannose-binding protein (Abmb) was discovered. Its discovery enriches the information and increases the interest in proteins with therapeutic potential from this mushroom. Furthermore, the A. bisporus genome reveals the possible occurrence of other lectins in this mushroom that may also have therapeutic potential. Most of these putative lectins belong to the same lectin groups as ABL and Abmb. Their relationship is discussed. Particular attention is addressed to ABL and Abmb, which have been explored for their potential in medicinal or pharmaceutical applications. ABL and Abmb have anti-proliferative activities toward cancer cells and a stimulatory effect on the immune system. Possible scenarios for their use in therapy and modification are also presented.

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 comprehensive review on tyrosinase inhibitors

Tyrosinase is a multi-copper enzyme which is widely distributed in different organisms and plays an important role in the melanogenesis and enzymatic browning. Therefore, its inhibitors can be attractive in cosmetics and medicinal industries as depigmentation agents and also in food and agriculture industries as antibrowning compounds. For this purpose, many natural, semi-synthetic and synthetic inhibitors have been developed by different screening methods to date. This review has focused on the tyrosinase inhibitors discovered from all sources and biochemically characterised in the last four decades.

Natural and Bioinspired Phenolic Compounds as Tyrosinase Inhibitors for the Treatment of Skin Hyperpigmentation: Recent Advances

One of the most common approaches for control of skin pigmentation involves the inhibition of tyrosinase, a copper-containing enzyme which catalyzes the key steps of melanogenesis. This review focuses on the tyrosinase inhibition properties of a series of natural and synthetic, bioinspired phenolic compounds that have appeared in the literature in the last five years. Both mushroom and human tyrosinase inhibitors have been considered. Among the first class, flavonoids, in particular chalcones, occupy a prominent role as natural inhibitors, followed by hydroxystilbenes (mainly resveratrol derivatives). A series of more complex phenolic compounds from a variety of sources, first of all belonging to the Moraceae family, have also been described as potent tyrosinase inhibitors. As to the synthetic compounds, hydroxycinnamic acids and chalcones again appear as the most exploited scaffolds. Several inhibition mechanisms have been reported for the described inhibitors, pointing to copper chelating and/or hydrophobic moieties as key structural requirements to achieve good inhibition properties. Emerging trends in the search for novel skin depigmenting agents, including the development of assays that could distinguish between inhibitors and potentially toxic substrates of the enzyme as well as of formulations aimed at improving the bioavailability and hence the effectiveness of well-known inhibitors, have also been addressed.

Agaricus bisporus mannose binding protein is not an agglutinating protein

Agaricus bisporus mannose binding protein (Abmb) demonstrates permeability to epithelial monolayer barrier of the intestine, resistance to gastrointestinal tract conditions and to proteolysis therefore it holds potential as a drug carrier for oral route administration. Abmb also display antiproliferative activity to breast cancer cells and stimulation of immune system thus could potentially be also developed for therapeutic purpose. It is not immunogenic or toxic thereby safe for use. In this paper we further provide evidence that Abmb also lacks of agglutinating activity despite sharing high structural homology to lectins. Abmb is thereby the only mannose specific binding protein that is not member of lectin family. This evidence provides further support on the use of Abmb as pharmaceutical or medicinal agent. Its molecular globularity that may contribute to its lack of agglutination capacity was also evaluated.

Orf239342 from the mushroom Agaricus bisporus is a mannose binding protein

A recently discovered lectin-like protein from mushroom tyrosinase designated as orf239342 inhibits proliferation of the MCF-7 breast cancer cells. This characteristic is likely derived from its ability to recognize sugar entity on the cell surface. Thereby, the binding specificity of orf239342 to sugars was studied. Orf239342 was found to bind specifically to mannose upon analysis with the surface plasmon resonance technique. Finally, our in vitro study showed that mannose impeded orf239342 ability to inhibit proliferation of the MCF-7 breast cancer cells, providing further evidence for the mannose binding onto the protein. Our finding is a breakthrough to characterise orf239342 i.e. to define its functioning in the mushroom, association to the tyrosinase, or even possible application in breast cancer therapy. In addition, the finding allows the more appropriate designation of the protein as Agaricus bisporus mannose binding-protein (AbMb).

Bioconjugation of Captopril-Light Subunit of Agaricus bisporus Mushroom Tyrosinase: Characterization and Potential Use as a Drug Carrier for Oral Delivery

We show that a lectin like protein from the mushroom Agaricus bisporus (LSMT) is capable to permeate the epithelial monolayer barrier of the intestine ex vivo. The protein is not toxic or immunogenic upon prolonged administration and elevated dose in mice. Thus, it could be a candidate as a drug carrier for oral administration. However, its permeability should be tested after the protein has been modified, mimicking the condition in which it is used as a drug carrier. The protein was conjugated to captopril, the selected model of a Biopharmaceutical Classification System (BCS) class III drug, with high solubility but poor permeability. The drug was conjugated to LSMT that had been modified with 4-succinimidyloxycarbonyl-alpha-methyl-2-pyridyldithiotoluene (SMPT) as a linker. The success of LSMT modification was confirmed with TLC and MS; the latter also indicated the amount of captopril molecule linked. The modified LSMT could permeate through the intestinal monolayer barrier, and thus could be absorbed in the intestine after modification. The modified protein appears to remain stable after incubation in simulated gastrointestinal fluids. This pioneering work provides an essential basis for further development of the protein as a drug carrier for oral administration.

New insight into the allosteric effect of L-tyrosine on mushroom tyrosinase during L-dopa production

Kinetics studies of L-tyrosine (LTy) ortho-hydroxylation by mushroom tyrosinase (MT) confirmed that MT was severely, but not completely, inhibited at higher concentrations of LTy. Despite the availability of the crystal structure reports, no allosteric site has been identified on MT. To examine the assumption that a non-specific binding site works as a regulatory site, docking simulations were run for the second molecule of L-tyrosine (LTy₂) on the complexes of the first L-tyrosine molecule (LTy₁) with the heavy chain (H) of MT (LTy₁/HMT) and its dimer with the light chain (Ty₁/LHMT). In both, LTy₂ occupied a non-specific binding site (MTPc). MD simulations revealed LTy₂/HMT/LTy₁ and LTy₂/LHMT/LTy₁ were stable. Binding free-energy analysis supported the formation of LTy₂/HMT/LTy₁ and LTy₂/LHMT/LTy₁ at higher concentrations of LTy and disclosed the importance of ΔE_elec and ΔG_polar during binding of LTy₂ to MTPc. Upon LTy₂ binding to MTPc, the Cu-Cu distance remained unchanged while the spatial position of LTy₁ in the active site (MTPa) changed so that it would not be able to participate in ortho-hydroxylation. This study suggests a tuning role for L chain during binding of the ligands to MTPa and MTPc. Given these results, a plausible mechanism was proposed for the MT substrate inhibition.

Structure-Activity Relationships of Thiazolyl Resorcinols, Potent and Selective Inhibitors of Human Tyrosinase

Tyrosinase inhibitors are of great clinical interest as agents for the treatment of hyperpigmentary disorders; however, most compounds described in the literature lack clinical efficiency due to insufficient inhibitory activity against human tyrosinase (hTyr). Recently, we reported that thiazolyl resorcinols (4-resorcinylthiazol-2-amines and -amides) are both selective and efficacious inhibitors of hTyr in vitro and in vivo. Here, we measured dose-activity profiles of a large number of thiazolyl resorcinols and analogous compounds to better understand the molecular basis of their interaction with hTyr. We show that both the resorcinyl moiety and the thiazole ring must be intact to allow efficient inhibition of hTyr, while the substituents at the thiazole 2-amino group confer additional inhibitory activity, depending on their size and polarity. The results of molecular docking simulations were in excellent agreement with the experimental data, affording a rationale for the structural importance of either ring. We further propose that a special type of interaction between the thiazole sulfur and a conserved asparagine residue is partially responsible for the superior inhibitory activity of thiazolyl resorcinols against hTyr.

Study of response of Swiss Webster mice to light subunit of mushroom tyrosinase

The light subunit of mushroom, Agaricus bisporus, tyrosinase (LSMT), has been identified as an extrinsic component of the enzyme. Its function is unknown, but it can cross an epithelial cell layer, which suggests that it can be absorbed by the intestine. A similar capability has been demonstrated for the HA-33 component of the progenitor toxin from Clostridium botulinum, which is the closest structural homolog of LSMT. Unlike HA-33, LSMT appears to be non-immunogenic as shown by preliminary tests in Swiss Webster mice. We investigated the immunogenicity and histopathology of LSMT in mice to determine its safety in vivo. LSMT did not evoke generation of antibodies after prolonged periods of intraperitoneal administration. Histopathological observations confirmed the absence of responses in organs after twelve weekly administrations of LSMT. We found that LSMT is not toxic and is less immunogenic than the C. botulinum HA-33 protein, which supports further research and development for pharmaceutical application.

Biological responses in Balb/c mice after long-term parenteral administration of the light subunit of mushroom tyrosinase

Light subunit of mushroom tyrosinase (LSMT) is a protein of unknown function from mushroom Agaricus bisporus that has been demonstrated to permeate through rat intestine ex vivo. Thus, it can be absorbed in the intestine, thereby holding a promise as a drug carrier for oral administration, similar to HA-33 protein from botulinum, one of the closest structural homologs of LSMT. However, the safety of LSMT should be ensured prior to its use. Here, we described biological response of LSMT upon weekly intraperitoneal administration of 50 μg/day to the Balb/c mice for 12 weeks. Motoric and behavior profiles, as well as the index of main organs (liver, spleen, lung, heart, and kidney), and body weight, were not significantly changed as compared with the control group. Also, no IgG was detected in the serum. The results suggest that LSMT is safe for further development.