Chapter 10- Imi Biochem Flashcards
(51 cards)
Collagen and elastin form
connective tissue- protein fibers embedded in a matrix of proteoglycans (ground substances)
Function of collagen
Provide support for the organs and other structures of the body
The proteins and proteoglycans are synthesized by connective tissue cells
fibroblasts (generalized connective tissue), chondroblasts (cartilage), and osteoblasts (bone)
Collagen type I distribution in what tissues
bone, tendon, skin, dentin, fascia, arteries
Collagen type II distribution in what tissues
cartilage, vitreous humor
Collagen type III distribution in what tissues
skin, blood vessels, uterus
Collagen type IV distribution in what tissues
basement membrane
Collagen type V distribution in what tissues
skin, placenta, blood vessels, chorion uterus
Synthesis of collagen
INTRACELLULAR STAGE consists of the production of procollagen from precursor polypeptide chains that undergo the sequence of hydroxylation (requires vit C), glycosylation (galactosyl and glucose sugars added to hydroxylysyl residues), formation of a triple helix, and secretion. The hydroxylation requires vitamin C EXTRACELLULAR STAGE consists of the conversion of procollagen to tropocollagen by limited proteolysis from the amino and carboxyl termini, self-assembly of tropocollagen molecules into fibrils, and finally cross-linking of the fibrils to form collagen fibers facilitated by lysyl oxidase requiring copper cofactor
in collagen the a.a. acid arrangement must have
every third a.a. must be glycine
Types of Ehlers-Dalos syndrome
6 major types: hypermobility, classical, vascular, kyphoscoliosis, arthrochalasia, dermatospraxis
Osteogenesis imperfecta due to
lack of type I collagen
Scurvy due to
vitamin c deficiency, unable to hydroxylate lysine and proline
collagen cross-linking occurs by
derived from lysyl and hydroxylysyl amino acid residues. First, oxidative deamination of the -NH2 group of two amino acids forming corresponding aldehyde-containing residues allysine, and hydroxyallysine. Second aldehyde groups react spontaneously with each other forming collagen cross links. first reaction is copper dependent and occurs extracellularly by lysyl oxidase
Elastin
Connective tissue protein, extensively interconnected, rubbery network resulting in connective tissue elasticity
Elastin rich in
proline and lysine
elastic fibers composed of
elastin & glycoprotein microfibrils
Elastin can be found in
lungs, the walls of large arteries, and elastic ligaments
Structure of elastin
Tropoelastin interact with fibrillin (defects causes marfan syndrome), desmosine cross-link by lysyl oxidase
Role of alpha 1-antitrypsin in elastin degradation
protease inhibitor, >90% of plasma alpha 1-globin fraction, major role of inhibiting neutrophil elastase, synthesized in the liver, monocytes, alveolar macrophages
Role of alpha 1 antitrypsin in the lungs
inhibit elastase to prevent alveolar wall damage destruction that would lead to emphysema
Emphysema resulting from alpha 1 antitrypsin deficiency
2~5% of emphysema patients due to genetic defects, autosomal recessive inheritance GAG->AAG (Glu->Lys) at 342 (E342K): the most widespread
Smokers with alpha 1 antitrypsin deficiency
inactivate Met of alpha 1 antitrypsin
alpha 1 antitrypsin deficiency treatment
weekly IV administration of alpha 1 antitrypsin
