GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

12. METABOLIC ACTIVITY OF AEROBIC HETEROTROPHS

12.6. INCOMPLETE OXIDATION

12.6.5. Formation of secondary metabolites

12.6.5.4. Lectins of microbial origin

Lectins are carbohydrate-binding Proteins characterized by a defined carbohydrate Specificity. The ability to interact with a specific carbohydrate is a fundamental characteristic of lectins. Lectins are used as Pharmaceuticals, diagnostic agents, and analytical Reagents. The most extensively studied biological reactions involving lectins include: agglutination of erythrocytes and other Cell types; adhesive activity; mitogenic stimulation of lymphocytes; phagocytic activity; enzymatic activity; and toxicity toward Eukaryotic Cells.

Until recently, plants and animal Tissues were the primary sources of lectins. However, even among these sources, There is a shortage of lectins with rare carbohydrate specificities (toward fucose, uronic acids, and sialic acids). Sialic acids (N-acetylneuraminic and N-glycolylneuraminic acids) can be viewed as Condensation products of N-acetylglucosamine and pyruvic acid. Sialic acids do not occur in a free state; rather, they are components of Glycoproteins and Glycoconjugates in biological fluids, and form an integral part of The Introduction/5.html">Eukaryotic Cell surface.

The technology for producing extracellular sialospecific bacterial lectins (developed in the 1980s) is an achievement of the Institute of Microbiology and Virology of the National Academy of Sciences of Ukraine. Representatives of the genus Bacillus (Bacillus subtilis) serve as producers of these unique lectins. Notably, the ability to synthesize lectins was discovered in saprophytic Bacteria for the first time.

Chemically, sialospecific bacillary lectins are glycoproteins containing up to 10% CARBOHYDRATES. They are heterogeneous in molecular weight: purified lectins contain components with molecular weights ranging from 31,000 to 70,000. The Molecular Weight of crude lectins does not exceed 15,000–19,000.

Bacterial lectins can be intracellular, cell surface-associated, or extracellular. Extracellular lectins found in the culture broth are of the greatest interest for biotechnology, as their isolation is simpler than that of cell-associated ones. The concentration of lectins in the culture broth is relatively low, typically not exceeding 100 mg/L.