An Update of Lectins from Marine Organisms: Characterization, Extraction Methodology, and Potential Biofunctional Applications

Abstract

Lectins are a unique group of nonimmune carbohydrate-binding proteins or glycoproteins that exhibit specific and reversible carbohydrate-binding activity in a non-catalytic manner. Lectins have diverse sources and are classified according to their origins, such as plant lectins, animal lectins, and fish lectins. Marine organisms including fish, crustaceans, and mollusks produce a myriad of lectins, including rhamnose binding lectins (RBL), fucose-binding lectins (FTL), mannose-binding lectin, galectins, galactose binding lectins, and C-type lectins. The widely used method of extracting lectins from marine samples is a simple two-step process employing a polar salt solution and purification by column chromatography. Lectins exert several immunomodulatory functions, including pathogen recognition, inflammatory reactions, participating in various hemocyte functions (e.g., agglutination), phagocytic reactions, among others. Lectins can also control cell proliferation, protein folding, RNA splicing, and trafficking of molecules. Due to their reported biological and pharmaceutical activities, lectins have attracted the attention of scientists and industries (i.e., food, biomedical, and pharmaceutical industries). Therefore, this review aims to update current information on lectins from marine organisms, their characterization, extraction, and biofunctionalities.

Keywords: adhesins; bio-functional roles; characterization; extraction and purification; hemagglutinins; immunomodulation; marine lectins.

Figure 1

Typical crystal structures of (A) rhamnose-binding lectin CLS3 from chum salmon (Oncorhynchus keta) [21], (B) F-lectin (fucolectin) from striped bass (Morone saxatilis) serum [22], (C) carp fishelectin (C-type lectin) [23], (D) zebrafish (Dario rerio) galectin-1-L2 [24], (E) Mytilus californianus galactose-binding lectin [25], (F) zebrafish (D. rerio) Dln1 (mannose-binding lectin) [26]. Individual images were obtained from Protein Data Bank (PDB, https://www.rcsb.org/, accessed on 20 June 2022).

Figure 2

Schematic presentation of lectin extraction and purification process.

Figure 3

Biofunctional and immunopotential roles of marine lectin.

Figure 4

Cell wall structure of Gram-positive (A) and Gram-negative (B) bacteria. Antibacterial mechanism showing lectin binding to bacterial cells and subsequent inhibition (C).

Figure 5

Schematic diagram of the mechanism of entry of SARS-CoV-2, viral replication, and viral RNA packing in a human cell (modified from [197]). The red line indicates the inhibition sites of SARS-CoV-2 by fish lectins. Copyright © 2020 Informa UK Limited, trading as Taylor & Francis Group.

Figure 6

Mechanism of lectin anti-viral activity targeted different steps in the virus life cycle (redrawn from [202] with permission, lisence no. 5337420221584. Copyright © 2021 Elsevier B.V. All rights reserved.

Figure 7

Cellular function of lectins as immunity enhancer. Abbreviations: IL-1β: Interleukin 1 beta, NADPH: Reduced nicotinamide adenine dinucleotide phosphate, CPLA2: Cytosolic Phospholipase A2, COX: Cyclooxygenase, NETosis: Neutrophil Extracellular Traps mediated necrosis, MHC: Major Histocompatibility Complex, CD4: Cluster of Differentiation 4, CD8: Cluster of Differentiation 8.

Figure 8

Direct recognition of pathogens and production of pro-inflammatory cytokines. Abbreviations: FAS: Fas receptor, FASL: Fas ligand.