The Biological Action and Structural Characterization of Eryngitin 3 and 4, Ribotoxin-like Proteins from Pleurotus eryngii Fruiting Bodies.

Ribotoxin-like proteins (RL-Ps) are specific ribonucleases found in mushrooms that are able to cleave a single phosphodiester bond located in the sarcin-ricin loop (SRL) of the large rRNA. The cleaved SRL interacts differently with some ribosomal proteins (P-stalk). This action blocks protein synthesis because the damaged ribosomes are unable to interact with elongation factors. Here, the amino acid sequences of eryngitin 3 and 4, RL-Ps isolated from Pleurotus eryngii fruiting bodies, were determined to (i) obtain structural information on this specific ribonuclease family from edible mushrooms and (ii) explore the structural determinants which justify their different biological and antipathogenic activities. Indeed, eryngitin 3 exhibited higher toxicity with respect to eryngitin 4 against tumoral cell lines and model fungi. Structurally, eryngitin 3 and 4 consist of 132 amino acids, most of them identical and exhibiting a single free cysteinyl residue. The amino acidic differences between the two toxins are (i) an additional phenylalanyl residue at the N-terminus of eryngitin 3, not retrieved in eryngitin 4, and (ii) an additional arginyl residue at the C-terminus of eryngitin 4, not retrieved in eryngitin 3. The 3D models of eryngitins show slight differences at the N- and C-terminal regions. In particular, the positive electrostatic surface at the C-terminal of eryngitin 4 is due to the additional arginyl residue not retrieved in eryngitin 3. This additional positive charge could interfere with the binding to the SRL (substrate) or with some ribosomal proteins (P-stalk structure) during substrate recognition.

The Structural Characterization and Antipathogenic Activities of Quinoin, a Type 1 Ribosome-Inactivating Protein from Quinoa Seeds.

Quinoin is a type 1 ribosome-inactivating protein (RIP) we previously isolated from the seeds of pseudocereal quinoa (Chenopodium quinoa) and is known as a functional food for its beneficial effects on human health. As the presence of RIPs in edible plants could be potentially risky, here we further characterised biochemically the protein (complete amino acid sequence, homologies/differences with other RIPs and three-dimensional homology modeling) and explored its possible defensive role against pathogens. Quinoin consists of 254 amino acid residues, without cysteinyl residues. As demonstrated by similarities and homology modeling, quinoin preserves the amino acid residues of the active site (Tyr75, Tyr122, Glu177, Arg180, Phe181 and Trp206; quinoin numbering) and the RIP-fold characteristic of RIPs. The polypeptide chain of quinoin contains two N-glycosylation sites at Asn115 and Asp231, the second of which appears to be linked to sugars. Moreover, by comparative MALDI-TOF tryptic peptide mapping, two differently glycosylated forms of quinoin, named pre-quinoin-1 and pre-quinoin-2 (~0.11 mg/100 g and ~0.85 mg/100 g of seeds, respectively) were characterised. Finally, quinoin possesses: (i) strong antiviral activity, both in vitro and in vivo towards Tobacco Necrosis Virus (TNV); (ii) a growth inhibition effect on the bacterial pathogens of plants; and (iii) a slight antifungal effect against two Cryphonectria parasitica strains.

Hortensins, Type 1 Ribosome-Inactivating Proteins from Seeds of Red Mountain Spinach: Isolation, Characterization, and Their Effect on Glioblastoma Cells.

Ribosome inactivating proteins (RIPs) are specific N-ß-glycosylases that are well-characterized in plants. Their enzymatic action is to damage ribosomes, thereby blocking protein translation. Recently, several research groups have been working on the screening for these toxins in edible plants to facilitate the use of RIPs as biotechnological tools and biopesticides and to overcome public prejudice. Here, four novel monomeric (type 1) RIPs have been isolated from the seeds of Atriplex hortensis L. var. rubra, which is commonly known as edible red mountain spinach. These enzymes, named hortensins 1, 2, 4, and 5, are able to release the ß-fragment and, like many other RIPs, adenines from salmon sperm DNA, thus, acting as polynucleotide:adenosine glycosidases. Structurally, hortensins have a different molecular weight and are purified with different yields (hortensin 1, ~29.5 kDa, 0.28 mg per 100 g; hortensin 2, ~29 kDa, 0.29 mg per 100 g; hortensin 4, ~28.5 kDa, 0.71 mg per 100 g; and hortensin 5, ~30 kDa, 0.65 mg per 100 g); only hortensins 2 and 4 are glycosylated. Furthermore, the major isoforms (hortensins 4 and 5) are cytotoxic toward human continuous glioblastoma U87MG cell line. In addition, the morphological change in U87MG cells in the presence of these toxins is indicative of cell death triggered by the apoptotic pathway, as revealed by nuclear DNA fragmentation (TUNEL assay).

Isolation, Characterization, and Biocompatibility of Bisporitin, a Ribotoxin-like Protein from White Button Mushroom (Agaricus bisporus).

White button mushroom (Agaricus bisporus (J.E. Lange) Imbach) is one of the widely consumed edible mushrooms. Indeed, A. bisporus fruiting bodies are a rich source of nutrients and bioactive molecules. In addition, several enzymes with biotechnological applications are found in A. bisporus (e.g., enzymes for lignocellulose degradation). Here, a novel ribotoxin-like protein (RL-P) from the edible mushroom A. bisporus was purified and characterized. This RL-P, named bisporitin, is a monomeric protein (17-kDa) exhibiting specific ribonucleolytic activity by releasing the α-fragment (hallmark of RL-Ps) when incubated with rabbit ribosomes. In addition, bisporitin shows magnesium-dependent endonuclease activity and displays a similar far-UV CD spectrum as ageritin, the prototype of RL-Ps, isolated from Cyclocybe aegerita fruiting bodies. Interestingly, bisporitin is the first member of RL-Ps to have noticeably lower thermal stability (Tm = 48.59 ± 0.98 °C) compared to RL-Ps isolated in other mushrooms (Tm > 70 °C). Finally, this protein is only partially hydrolyzed in an in vitro digestive system and does not produce adverse growing effects on eukaryotic cell lines. This evidence paves the way for future investigations on possible bioactivities of this RL-P in the digestive system.

An Updated Review of Bioactive Peptides from Mushrooms in a Well-Defined Molecular Weight Range.

Here, we report the current status of the bioactive peptides isolated and characterized from mushrooms during the last 20 years, considering 'peptide' a succession from to 2 to 100 amino acid residues. According to this accepted biochemical definition, we adopt ~10 kDa as the upper limit of molecular weight for a peptide. In light of this, a careful revision of data reported in the literature was carried out. The search revealed that in the works describing the characterization of bioactive peptides from mushrooms, not all the peptides have been correctly classified according to their molecular weight, considering that some fungal proteins (>10 kDa MW) have been improperly classified as 'peptides'. Moreover, the biological action of each of these peptides, the principles of their isolation as well as the source/mushroom species were summarized. Finally, this review highlighted that these peptides possess antihypertensive, antifungal, antibiotic and antimicrobial, anticancer, antiviral, antioxidant and ACE inhibitory properties.

Biochemical Traits, 1H NMR Profile and Residual DNA Content of 'Asprinio', White Wine from Campania Region (Southern Italy).

'Asprinio' is a white dry wine characteristic for its acidity and aromatic flavour, known as emerging DOP wine in Southern Italy. Nevertheless, little information is available on the metabolomic profile of this wine. Thus, in this paper we evaluated the colourimetric parameters, 1H NMR profiles and free amino acids content of 'Asprinio' wines, bottled by two different wineries (hereafter 'Asprinio_A' and 'Asprinio_B') collected in 2019 and 2020, using 'Greco di Tufo' for comparison. The colourimetric parameters are similar for both 'Asprinio' wines and differ from 'Greco di Tufo' wines. On the other hand, both 1H NMR and free amino acid content profiles show different chemometric profiles among the three wines analysed, although the profiles are similar for both vintages. Moreover, the multivariate analyses carried out highlight differences between 'Asprinio_A' and 'Asprinio_B', which exbibit also different residual yeast and plant DNA. Overall, considering that the two-manufacturing wineries use 100% 'Asprinio' grape, the difference retrieved between the two 'Asprinio' wines could be explained by the different grapevine training systems: 'vite maritata' (training system inherited from Etruscans) for 'Asprinio_A' and 'guyot' for 'Asprinio_B'.

Isolation, Characterization and Biological Action of Type-1 Ribosome-Inactivating Proteins from Tissues of Salsola soda L.

Ribosome-inactivating proteins (RIPs) are known as RNA N-glycosylases. They depurinate the major rRNA, damaging ribosomes and inhibiting protein synthesis. Here, new single-chain (type-1) RIPs named sodins were isolated from the seeds (five proteins), edible leaves (one protein) and roots (one protein) of Salsola soda L. Sodins are able to release Endo's fragment when incubated with rabbit and yeast ribosomes and inhibit protein synthesis in cell-free systems (IC50 = 4.83-79.31 pM). In addition, sodin 5, the major form isolated from seeds, as well as sodin eL and sodin R, isolated from edible leaves and roots, respectively, display polynucleotide:adenosine glycosylase activity and are cytotoxic towards the Hela and COLO 320 cell lines (IC50 = 0.41-1200 nM), inducing apoptosis. The further characterization of sodin 5 reveals that this enzyme shows a secondary structure similar to other type-1 RIPs and a higher melting temperature (Tm = 76.03 ± 0.30 °C) and is non-glycosylated, as other sodins are. Finally, we proved that sodin 5 possesses antifungal activity against Penicillium digitatum.

Myoglobin from Atlantic and Tinker mackerels: Purification, characterization and its possible use as a molecular marker.

Here, we report the characterization (purification, autoxidation rate, pseudoperoxidase activity) and amino acid sequence determination of S. scombrus (Atlantic mackerel) and S. colias (Tinker mackerel) mioglobins (Mbs), considering the increasing consumption of fresh and canned mackerel meat and Mb implication in meat storage (e.g.: browning and lipid oxidation). We found that Atlantic mackerel Mb has major autoxidation rate (0.204 ± 0.013 h-1) compared to Tinker mackerel Mb (0.140 ± 0.009 h-1), while the pseudoperoxidase activity is major for Tinker mackerel (Km: 87.71 ± 7.19 µM; kcat: 0.32 s-1) Mb with respect to Atlantic mackerel (Km: 96.08 ± 6.91 µM; kcat: 0.50 s-1). These functional differences are confirmed by primary structure determination, in which six amino acid substitutions are found, with the first N-terminal amino acid residue acetylated. Furthermore, we predicted by AphaFold 3D model both fish Mbs and used them to investigate the possible structural differences. In addition, phylogenetic analysis using Mb sequences from Scombridae family confirms that Atlantic and Tinker mackerels are two distinct species. Finally, an analytic qualitative RP-HPLC method to distinguish S. scombrus and S. colias specimens was developed considering the different retention times of the two mackerel apoMbs.

Ca2+ as activator of pseudoperoxidase activity of pigeon, Eurasian woodcock and chicken myoglobins: New features for meat preservation studies.

Myoglobin (Mb), hemeprotein that binds dioxygen in muscle, affects meat colour. Moreover, in presence of peroxides, metMb is a potent oxidant involved in oxidative rancidity in meat. Here, following pigeon Mb purification and primary structure mass spectroscopy characterization, we determined its autoxidation rate and pseudoperoxidase activity with respect to chicken and E. woodcock Mbs. The three Mbs exhibit different autoxidation rates (0.153-h-1 pigeon, 0.194-h-1 chicken and 0.220-h-1 E. woodcock Mbs) and similar specificity constant (9.86x103 M-1s-1 pigeon, 8.81x103 M-1s-1 chicken and 9.90x103 M-1s-1 E. woodcock Mbs), considering their pseudoperoxidase activity. Moreover, for the first time, we detected an increase in pseudoperoxidase activity in presence of Ca2+, particularly at pH 5.8. NMR and CD data indicate that the nonspecific Ca2+ binding induces small local structural rearrangements that in turn slightly reduce pigeon Mb thermal stability. However, considering Ca2+ concentration variations before and post-mortem, this finding must be considered for meat preservation.

Valle Agricola Chickpeas: Nutritional Profile and Metabolomics Traits of a Typical Landrace Legume from Southern Italy.

Chickpea (Cicer arietinum L.) from Valle Agricola is a legume cultivated in Southern Italy whose intake is strictly linked to rural traditions. In order to get new biochemical insight on this landrace and to promote its consumption and marketing, nutritional values (moisture content, total proteins, lipids, total and free amino acids) and metabolic traits are deeply investigated. Valle Agricola chickpea is nutritionally rich in proteins (19.70 g/100 g) and essential amino acids (7.12 g/100 g; ~40% of total). Carbohydrates, whose identity was unraveled by means of UHPLC-HR MS/MS analysis, were almost 60% of chemicals. In particular, a di-galactosylglycerol, a pinitol digalactoside, and a galactosylciceritol were found as constitutive, together with different raffinose-series oligosaccharides. Although lipids were the less constitutive compounds, glycerophospholipids were identified, while among free fatty acids linoleic acid (C18:2) was the most abundant, followed by oleic (C18:1) and palmitic (C16:0) acids. Isoflavones and hydroxybenzoic acid derivatives were also detected. Valle Agricola chickpeas showed very good levels of several mineral nutrients, especially magnesium (164 mg/100 g), potassium (748 mg/100 g), calcium (200 mg/100 g), zinc (4.20 mg/100 g) and manganese (0.45 mg/100 g). The boiling process favorably decreases anti-trypsin and anti-chymotrypsin activities, depleting this precious seed of its intrinsic antinutritional factors.