Two of the most important nutrients that we need to supply to our body routinely are protein and carbohydrate. Both are essential as energy sources and also as building blocks of the cells of the body. In our food, protein and carbohydrate molecules may come in many ways, such as glycoproteins and proteoglycans.
Both glycoproteins and proteoglycans are chemical chains that feature proteins and carbohydrate units. The carbohydrate units may vary from monosaccharides to disaccharides to polysaccharides, bound covalently to the proteins. So, what are the differences between glycoproteins and proteoglycans?
A glycoprotein is a protein to which carbohydrate units are covalently bound through glycosidic bounds. In the human body, glycoproteins are very important. They are part of the membranes and Golgi apparatus in cells, and they also act as receptors and adhesion molecules. Some hormones, like FSH, LH, EPO, and TSH, are also considered glycoproteins.
On the other hand, a proteoglycan is composed of a protein core with one or more glycosaminoglycan (GAG) chains covalently attached. As the effect, proteoglycans tend to be larger than glycoproteins. Proteoglycans are found in connective tissues, contributing to the organization and physical properties of the extracellular matrix.
Glycoprotein vs Proteoglycan
|- Has short, highly branched chains with no repeating unit||- Has long unbranched chains with disaccharide units as repeating structures|
|- The carbohydrate content is 50% – 60%||- The carbohydrate content is 10% – 15%|
|- May or may not be negatively charged||- Is negatively charged due to the sulfate and uronic acid groups|
|- Found mainly within cells||- Found mainly in connective tissues|
|- Functions in cellular recognition||- Is important in the modulation of cellular development processes|
So, glycoprotein is a short but highly branched molecule with no repeating unit, found mainly within cells. Meanwhile, proteoglycan has long, unbranched chains that feature disaccharide units as repeating structures. It is largely found in connective tissues.