Classification and Biological Functions of Glycoproteins

Glycoprotein is a protein containing oligosaccharide chains that are covalently linked to each other. The oligosaccharide chains are usually linked to the protein by glycosylation. Glycoproteins are commonly found in animals, plants and microorganisms, with a wide variety of species and functions.

They can be classified into three categories:

1. Soluble glycoproteins, which exist in intracellular fluid, various body fluids and mucus secreted by luminal glands. Soluble glycoproteins include enzymes (e.g. nucleases, proteases, glycosidases), peptide hormones (e.g. chorionic gonadotropin, luteinizing hormone, thyrotropin, erythropoietin), antibodies, complement, and certain growth factors, interferons, inhibitors, lectins and toxins.
2. Membrane bound glycoprotein, whose peptide chains are composed of hydrophobic peptides and hydrophilic peptides. The hydrophobic peptides can be one to several and are embedded in the membrane lipid bilayer through hydrophobic interactions. Membrane-bound glycoproteins include enzymes, receptors, lectins and transport proteins. These glycoproteins are often involved in cell recognition and can serve as surface markers or surface antigens for a particular cell or cells at a particular stage.
3. Structural glycoproteins, insoluble macromolecular glycoproteins in the extracellular matrix, such as collagen and various non-collagenous glycoproteins (fibronectin, laminin, etc.). They not only play a supporting, connecting and buffering role as structural components of the extracellular matrix, but also participate in cell recognition, adhesion and migration, and regulate cell proliferation and differentiation.

Biological function of glycoprotein

Their main biological function is the biological recognition of cells or molecules. For example, sperm need to recognize the corresponding glycoprotein on the egg cell membrane when the egg is fertilized. Receptor proteins, tumor cell surface antigens, etc. are also glycoproteins. The sugar chain of glycoprotein is also involved in maintaining its peptide chain in its natural conformation of biological activity and stabilizing the peptide chain structure, and endows the entire glycoprotein molecule with specific physicochemical properties (e.g., lubricity, viscoelasticity, resistance to heat inactivation, protease hydrolysis, and resistance to freezing).

Glycoproteins are associated with the occurrence and development of many diseases such as infections, tumors, cardiovascular diseases, liver diseases, kidney diseases, diabetes, and certain genetic diseases. Furthermore, the glycoproteins and glycolipids on the cell surface can be "shed" to the surrounding environment or enter the blood circulation, which can be used as abnormal markers to provide information for clinical diagnosis. Glycoproteins in body fluids often have specific or strong or weak changes when suffering from certain diseases, which can help in diagnosis or prognosis. For example, antibodies against specific glycan structures on the surface of specific cells can be used as targeted carriers of therapeutic drugs. The use of glycans (monosaccharides, oligosaccharides or glycopeptides) against infections and against tumor metastasis has also emerged.

In view of their important biological functions, researchers have developed many methods such as glycoprotein mass spectrometry detection to explore the structure and mechanisms of action of glycoproteins to help develop diagnostic, therapeutic, and prognostic tools for diseases.

Glycoproteins are already a very popular area of research, with more than 20,000 glycoprotein-related articles published in 2021. Creative Proteomics, a leader in glycoproteomics, can provide comprehensive glycoprotein analysis services to accelerate your research project.

Creative Proteomics has gradually grown into an integrated service provider with targeted lipidomics and untargeted lipidomics analysis services for researchers in pharmaceutical, biotechnology, agriculture, and nutrition industries.