Lectin Activity in Commonly Consumed Plant-Based Foods: Calling for Method Harmonization and Risk Assessment

Lectins are ubiquitous proteins characterized through their ability to bind different types of carbohydrates. It is well known that active lectins from insufficiently prepared legumes can cause adverse human health effects. The objective of this study was to determine the activity of lectins in samples across plant families representing commercially available edible plants, and the feasibility of inactivating lectins through soaking and boiling. Lectins were extracted from the plant families Adoxaceae, Amaranthaceae, Cannabaceae, Fabaceae, Gramineae, Lamiaceae, Linaceae, Pedaliaceae, and Solanaceae. A hemagglutination assay based on non-treated or trypsin treated rabbit erythrocytes was used to measure the lectin activity. The results showed the highest lectin activity in species from the Fabaceae family and demonstrated that soaking and boiling have an effect on the levels of active lectins. This is the first large study that combines lectin activity obtained from two different assays with raw and processed edible plants. In addition, we examined the current risk assessment, and regulations necessary for an adequate official reporting of results. We encourage the scientific community to further explore this field and agree on harmonized methods for analysis and interpretation, and hope that our methodology can initiate this development.

Trefoil Factor Family (TFF) Peptides

Trefoil factor family (TFF) peptides mainly consist of characteristic TFF domains, which contain about 40 amino acid residues, including 6 conserved cysteine residues. TFF peptides possess a single (mammalian TFF1 and TFF3), two (mammalian TFF2, Xenopus laevis xP2) or four TFF domains (X. laevis xP4). They exhibit lectin activities and are characteristic exocrine products of the mucous epithelia. Here, they play different roles for mucosal protection and the innate immune defense: TFF1 is a gastric tumor suppressor; TFF2 builds a lectin complex with the mucin MUC6, physically stabilizing the inner gastric mucus layer; and TFF3 forms a disulfide-linked heterodimer with IgG Fc binding protein (FCGBP), probably preventing the infiltration of microorganisms. Minor amounts of TFF peptides are endocrine products of the immune and nervous systems. Pathologically, TFF peptides are linked to inflammation. There are increasing indications that TFF peptides can antagonize cytokine receptors, such as receptors for IL-1β, IL-6, and TNFα (thereby acting as anti-inflammatory peptides). TFF peptides can probably also activate a variety of receptors, such as CXCR4. The TFF domain is a unique shuffled module which is also present in a number of mosaic proteins, such as zona pellucida proteins, sugar degrading enzymes and frog skin mucins. Here, their function seems to be defined by a lectin activity, which might even allow a role in fertilization.

BIOCHEMICAL CHARACTERISTIC OF SOLUBLE LECTINS IN CORN UNDER THE IMPACT OF WATER DEFICIT AND HYPERTHERMIA

Introduction. Drought and high temperature are two of the key factors of the environment limiting crop capacity of grains. Response of the plants to drought and high temperature is very complex and includes interaction between various molecular, physiological and biochemical processes. Synthesis of a number of proteins present under normal conditions, including lectins, increases along with synthesis of stress proteins under adverse conditions.Aim. The goal of our study is to identify the changes in the activity and biochemical characteristics of soluble lectins in maize seedlings with different drought tolerance under water and heat stress in order to create new biochemical methods for assessing drought tolerance.Methods. Three-day young sprouts of corn lines (Zea mays L.) with different levels of drought tolerance were used in the research: drought-tolerant lines Od 329, IK107 zM, non-drought tolerant lines GK 26, IK107VS3 / 66. Lectin activity was defined on the basis of their ability to agglutinate trypsinized erythrocytes of white rats. Electrophoresis was performed in 10 % PAGE following the Laemmli method.Results. The study enabled us to identify increase in soluble lectin activity (244-281 % of the reference value) under the given stress factors in drought-tolerant lines, and decrease in soluble lectin activity (39 - 79 % of reference value) under the given stress factors in non-drought-tolerant lines. Soluble lectins were isolated and purifid using salting out with ammonium sulfate, dialysis and affiity chromatography. The molecular weight of the isolated soluble lectins is in the range of 50-60 kDa. The isolated lectins had a high affiity for N-acetylglucosamine and D-fructose-6-phosphate.Conclusion. Therefore, it has been established that corn lines with positively different levels of drought tolerance are characterized by varying activity of soluble lectins.

All major cholesterol-dependent cytolysins use glycans as cellular receptors

Cholesterol-dependent cytolysins (CDCs) form pores in cholesterol-rich membranes, but cholesterol alone is insufficient to explain their cell and host tropism. Here, we show that all eight major CDCs have high-affinity lectin activity that identifies glycans as candidate cellular receptors. Streptolysin O, vaginolysin, and perfringolysin O bind multiple glycans, while pneumolysin, lectinolysin, and listeriolysin O recognize a single glycan class. Addition of exogenous carbohydrate receptors for each CDC inhibits toxin activity. We present a structure for suilysin domain 4 in complex with two distinct glycan receptors, P1 antigen and αGal/Galili. We report a wide range of binding affinities for cholesterol and for the cholesterol analog pregnenolone sulfate and show that CDCs bind glycans and cholesterol independently. Intermedilysin binds to the sialyl-TF O-glycan on its erythrocyte receptor, CD59. Removing sialyl-TF from CD59 reduces intermedilysin binding. Glycan-lectin interactions underpin the cellular tropism of CDCs and provide molecular targets to block their cytotoxic activity.

Repurposed Drugs That Block the Gonococcus-Complement Receptor 3 Interaction Can Prevent and Cure Gonococcal Infection of Primary Human Cervical Epithelial Cells

ABSTRACT In the absence of a vaccine, multidrug-resistant Neisseria gonorrhoeae has emerged as a major human health threat, and new approaches to treat gonorrhea are urgently needed. N. gonorrhoeae pili are posttranslationally modified by a glycan that terminates in a galactose. The terminal galactose is critical for initial contact with the human cervical mucosa via an interaction with the I-domain of complement receptor 3 (CR3). We have now identified the I-domain galactose-binding epitope and characterized its galactose-specific lectin activity. Using surface plasmon resonance and cellular infection assays, we found that a peptide mimic of this galactose-binding region competitively inhibited the N. gonorrhoeae-CR3 interaction. A compound library was screened for potential drugs that could similarly prohibit the N. gonorrhoeae-CR3 interaction and be repurposed as novel host-targeted therapeutics for multidrug-resistant gonococcal infections in women. Two drugs, methyldopa and carbamazepine, prevented and cured cervical cell infection by multidrug-resistant gonococci by blocking the gonococcal-CR3 I-domain interaction. IMPORTANCE Novel therapies that avert the problem of Neisseria gonorrhoeae with acquired antibiotic resistance are urgently needed. Gonococcal infection of the human cervix is initiated by an interaction between a galactose modification made to its surface appendages, pili, and the I-domain region of (host) complement receptor 3 (CR3). By targeting this crucial gonococcal–I-domain interaction, it may be possible to prevent cervical infection in females. To this end, we identified the I-domain galactose-binding epitope of CR3 and characterized its galactose lectin activity. Moreover, we identified two drugs, carbamazepine and methyldopa, as effective host-targeted therapies for gonorrhea treatment. At doses below those currently used for their respective existing indications, both carbamazepine and methyldopa were more effective than ceftriaxone in curing cervical infection ex vivo. This host-targeted approach would not be subject to N. gonorrhoeae drug resistance mechanisms. Thus, our data suggest a long-term solution to the growing problem of multidrug-resistant N. gonorrhoeae infections.

Characterization of Lectin from Colpomenia Sinuosa and Effect of Physico Chemical Parameters on Haemagglutination Activity

Lectin is a protein which has the ability to bind carbohydrates and named as haemagglutinin. Lectins with specific carbohydrate specificity have been purified from various plant tissues and other organisms and exploited extensively in many aspects of biochemistry and biomedicine. Similar to land plants, lectins from marine algae appear to be useful in some biological applications. Although several studies on lectins from marine algae have been reported till date, few lectins from algae have been characterized in detail. The present study was focused on the lectin isolated from C.sinuosa. The algal lectin has high sugar specificity with N-acetylglucosamine and higher enzyme activity with trypsin. This lectin was identified as CaCl2 dependent – ‘C’ type lectin and was sensitive to EDTA. Higher H.A titre value was observed with CaCl2 and the lower with MnCl2 and ZnCl2 . Significant lectin activity was observed between pH 7 to 8 and temperature between 20 to 40 O C

Trefoil factors share a lectin activity that defines their role in mucus

The trefoil factors (TFFs) are disulfide-rich mucosal peptides that protect the epithelium by promoting cell migration and increasing the viscoelasticity of the mucosa. Here we show that all TFFs are divalent lectins that recognise the GlcNAc-α-1,4-Gal disaccharide, which terminates type-III mucin-like O-glycans. Structural, mutagenic and biophysical data support a model of mucus viscoelasticity that features non-covalent cross-linking of glycoproteins by TFFs.