단백질 ≫ 단백질종류 ≫ 콜라겐

proteoglycan   

세포골격, ECM
- 증점(단순)다당류 , 복합다당류
- 세포는 Fiber 덩어리다 , 세포는 콜라겐 덩어리다
- 콜라겐 Collagen ,  콜라겐 조성 및 합성과정
- 엘라스틴 elastin,  Proteoglycan
- Fibronectin,  Laminins
- Integrins,  Cadherins

Glycosaminoglycans and Proteoglycans Are Components of the Extracellular Matrix

동물조직의 세포의 공간은 gel 같은 물질인 extracellular matrix로 채워져 있다. Glycosaminoglycan은 반복적인 disaccharide unit 로 구성된 linear polymer 이다. 2개의 monosaccharide 중 하나는 N-acetylglucosamine 또는 N-acetylgalactosamine 이고 나머지는 대부분의 경우 uronic acid, 대개 glucuronic acid 이다. Glycosaminoglycan 은 세포의 단백질과 결합하여 proteoglycan을 형성한다. Proteoglycan의 95% 이상은 polysaccharide이다.

* Glycosaminoglycan은 독립적인 negative charge(COO-, OSO3-)를 가지며, 따라서 repulsion 때문에 3차원 구조는 extended linear form이다.

1. proteoglycan matrix = highly hydrated, gel-like matrix composed of proteins with covalently attached
               glucoseamine polymers AND free polysaccharide chains
2. collagen and elastin fibers are enmeshed in  proteoglycan matrix
3.  glycoaminoglycans (GAGs) = free polysaccharides  of the proteoglycan matrix
    a. made from several repeating disaccharide units
                      (1) chondroitin sulfate,  (2) keratan sulfate, (3) hyaluronate
    b. repeating carbonhydrate units are highly charged and polar
                      (1) attract water,  (2) attract cations
                      (3) form a gelatinous matrix in which collagen and elastin fibrils are embedded
  4.  proteoglycans = proteins with covalently attached GAG
    a.  "mucoproteins" is another name
    b.  GAG bound periodically along length of protein
                         -GAG attached enzymatically outside of cell
    c.  GAG can vary
    d.  core proteins can vary
    e.  get great variety of different proteoglycans
    f.   core proteins highly variable in size
                        (1) MW varies from 10,000 to 500,000 daltons
    g.  number of GAG chains varies from 1 to 200 per core protein
    h.  typical GAG length about 800 monosaccharide units
    i.   crosslinking of proteoglycans can occur
                        (1) get huge covalently linked assembles
                                -higher magnification
                                -sometimes several millimeters thick!
  5. proteoglycans hold HUGE amounts of water
                 a. can hold 50X their dry weight in water
  6. proteoglycans resistant to compression
                 a. due to high water content
  7. free polymer of  hyaluronate lubricates joints
     a. hyaluronate exists as free molecule with 100s of repeating disaccharide units
    b. serves as lubricant in joints between moveable bones
    c. hyaluronate can be isolated and purified from the  combs of roosters
       (1) purified hyaluronate can be injected into joints to reduce friction and inflammation