- Discussion:
- biosynthesis of collagen is initiated w/
osteoblasts;
- these intracellular events involve protein synthesis on endoplasmic
reticulum to form 3 polypeptide chains, which make up protocollagen;
- protocollagen is hydroxylated to form procollagen, which is glyco-
sylated at the endoplasmic reticulum;
- degree of hydroxylation of the lysine residue is important in
that it will determine the number of crosslinks and therefore
strength of the collagen;
- procollagen is converted to a triple helix before secretion from cell
by microtubules;
- procollagen helices are actually longer than collagen molecules owing
to amino-terminal and carboxy-terminal endpieces that keep collagen
soluble while inside the cell;
- intracellular processes require more than eight enzymes, result
in over l50 modifications of each chain, and alter one-tenth
of the amino acids;
- once the
osteoblasts secretes procollagen, a procollagen
peptidase splits off the terminal endpieces, and polymerization and
maturation naturally follow;
- covalent bonds are formed between the adjacent collagen molecules both
within microfibrils and between adjacent microfibrils;
- these crosslinks determine maximal tensile strength of tissue
collagen & its subsequent solubility and thus extractability;
