What Are Proteoglycans?

Proteoglycan (PG) is a special type of glycoprotein, which consists of one or more glycosaminoglycans and a core protein covalently linked. In addition to glycosaminoglycan-containing glycan chains, proteoglycans also have some N- or (and) O-linked oligosaccharide chains. Proteoglycans are distributed not only on the extracellular matrix, but also on the cell surface and in secretory particles within the cell. ^[1]

Protein and

versus

except

Due to the different size and structure of core protein molecules,

As mentioned earlier, cartilage polymerizable proteoglycans can form typical proteoglycan aggregates based on HA molecules. Each polymerizable proteoglycan molecule (average Mr ~ 2.5 million) contains about 50 KS chains (M _r 10,000 ~ 15,000), about 100 CS chains (M _r 20,000 ~ 30,000) and several O -Linked oligosaccharide chains, which are distributed in different regions of the core protein (Mr 200,000 to 300,000), the entire molecule is shaped like a "test tube brush". Regularly bind a proteoglycan monomer (ie a core protein plus bound

include

Available in a series

Amino glycans and proteoglycans in the arterial wall are inherent factors that cause low-density lipoprotein and calcium deposition. The content of dermatan sulfate in the arterial wall increases with age, and can be combined with low-density lipoprotein at physiological pH and ionic strength. Aortic tissue with atherosclerotic plaques shows abnormally high levels of dermatan sulfate and is produced by smooth muscle cells that proliferate at the lesion.

Proteoglycans are also involved in tumorigenesis and metastasis. In some tumors, such as stromal tumors, nephroblastomas, breast cancer, and gliomas, the amount of hyaluronic acid synthesized and secreted by tumor cells increases, and the content of hyaluronic acid in body fluids (blood, urine) increases. It has certain diagnostic significance. Chondroitin sulfate is increased in tumor tissues such as liver, lung, breast, colon and prostate. In vitro experiments have shown that chondroitin sulfate can promote the growth of breast cancer; in vivo experiments have proved that it can promote the growth of Ehrlich ascites cancer. Chondroitin sulfate-degrading enzymes can inhibit the growth of Ehrlich ascites cancer. In short, the increase of hyaluronic acid and chondroitin sulfate in tumor tissue may be related to the uncontrolled proliferation. In contrast, heparan sulfate has the effect of inhibiting cell proliferation. In vitro experiments have demonstrated that heparan sulfate isolated from the liver or hepatic plasma membrane can inhibit the growth of liver cancer cells.

In human liver cancer, mouse myeloma, spontaneous breast cancer, and ascites-type liver cancer, it can be seen that the sulfated degree of heparan sulfate is reduced. This may not only affect its function of inhibiting cell proliferation, but may also weaken its affinity with fibronectin, laminin, and collagen, resulting in abnormal assembly of the matrix surrounding tumor cells, weakened adhesion between tumor cells, and tumors. Cells tend to detach from tumor tissue. This creates a prerequisite for tumor metastasis. In addition, an endoglycosidase that can degrade heparan sulfate exists in some metastatic tumors (such as melanoma). It can destroy heparan sulfate, and its degradation products are released into the blood. Coagulation activity can cause more than bleeding.

Congenital lack of enzymes that degrade aminoglycans (such as glycosidase or sulfatase) can cause aminoglycans or proteoglycans or their degradation products to accumulate in certain parts of the body, causing mucopolysaccharidosis.