The extracellular matrix is a complex combination of non-cellular materials that support biochemical and biomechanical processes in the tissues and organs. Among the components of the extracellular mix are two distinct types of biomolecules: proteoglycans and glycoproteins.


Immunology researchers
are primarily interested in these biomolecules due to their role in the human tissue processes and immune system function. For example, scientists have researched the effects of proteoglycans and glycoproteins on wound healing, liver cancer, viral pathogens, and many other areas.

 

Measuring Proteoglycans

Detecting proteoglycan in your tissue samples is a two-part process. First, properly prepare your tissue samples using an optimized assay buffer. Next, measure sulfated glycosaminoglycans with a simple colorimetric readout.

 

The Differences Between Proteoglycans & Glycoproteins

Learn more about the differences between proteoglycans and glycoproteins in the table below.

 ProteoglycansGlycoproteins
StructureCore protein covalently attached to one or more glycosaminoglycan chainsOligosaccharide chains covalently attached to proteins
LocationConnective tissuesCell surface
FunctionCombine with collagen to form cartilage, modulation of cellular developmentCell-to-cell recognition and signaling
Carbohydrate Content50–60%10–15%
ChargeCarbohydrate chains of proteoglycans are negatively chargedCarbohydrate chains of glycoproteins may or may not be negatively charged
SignificanceThe water associated with proteoglycans provides the cushion function of cartilage. The inability to sufficiently break down proteoglycans is linked to several genetic disorders and leads to other disease symptoms.Carbohydrate modifications are essential to proper functioning of proteins. Changes in glycosylation patterns are common in cancer cells. Carbohydrates can also affect the performance of therapeutic antibodies.
TypesChondroitin sulfate, dermatan sulfate, heparan sulfate, keratan sulfate, othersCollagens, mucins, transferrin, immunoglobulins, others

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6 Comments

  1. Hi Anne,
    This is a great post, but the numbers for the carbohydrate content are reversed. It’s 50-60% for the proteoglycans and 10-15% for most common glycoproteins (and things like uromodulin and most mucins would be 30+% sugars).
    Best,
    Jared Gerlach

    • Well I stand corrected. I don’t know where I found the higher percentage for glycoproteins but your figures make more sense to me, especially given the function of proteoglycans.

    • That’s a good question Lance. I was referring to articular cartilage when I wrote that, not thinking about other forms of cartilage. It could be that in a shark fin or external ear of a mammal there would be less glycosaminoglycan because those tissues are stiffened by the proteoglycans but not bearing weight as in articular cartilage. You could certainly check with a longer hydrolysis of the sample to be sure you have freed up all the GAG. With our tissue digestion kit we could clearly see an increase in glycosaminoglycan with increasing digestion time.

  2. I am a student and i have a doubt. If carbohydrates are core to glycoproteins then why is the amount of carbohydrates less in glycoproteins than proteoglycans?

    • I understand your doubt. I think of both glycoproteins and proteoglycans as having a protein core. One description of proteoglycans is to think of them like a test tube brush. The protein in the middle with the bristles being carbohydrate chains. With proteoglycans the proteins are usually longer and carbohydrates are placed at points along the protein sequence. In both cases the beginning is a protein but in the case of proteoglycans it is totally surrounded by carbohydrate.

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