Collagen impaired hydroxylation

Why does impaired hydroxylation have such devastating consequences Collagen synthesized in the absence of ascorbate is less stable than the normal protein. Studies of the thermal stability of synthetic polypeptides have been especially informative. Hydroxyproline stabilizes the collagen triple helix by forming interstrand hydrogen bonds. The abnormal fibers formed by insufficiently hydroxylated collagen contribute to the skin lesions and blood-vessel fragility seen in scurvy. 

Vitamin C deficiency results in an impairment in the hydroxylation of collagen. Properly hydroxylated collagen molecules self-associate to form a triple-helix structure within the cell (Figure 9.83). Collagen that is not hydroxylated and does not form the triple helix is not readily secreted from the cell. Its secretion is impaired. The underhydroxylated collagen tends not to build up in the cell but instead is rapidly degraded. Historically, one confusing aspect of vitamin C research was that the deficiency seemed not to result in an accumulation of abnormal... 

Why does impaired hydroxylation have such devastating consequences Collagen synthesized in the absence of ascorbate is less stable than the normal protein. Studies of the thermal stability of synthetic polypeptides have been... 

A requirement for ascorbic acid in collagen formation has been well documented. This, it has been suggested, results from a utilization of this vitamin in the formation of hydroxjrproline from bound proline in a precollagen peptide (137,138) or for formation of an activated hydroxyproline (139). Mitoma and Smith (140) showed, however, that while ascorbic acid deficiency impaired collagen synthesis hydroxylation of proline was not affected. 

C Ascorbic acid Coenzyme in hydroxylation of proline and lysine in collagen synthesis antioxidant enhances absorption of iron Scurvy—impaired wound healing, loss of dental cement, subcutaneous hemorrhage... 

L-ascorbic acid deficiency results in reduced hydroxylation of proline and lysine, thus destabilizing the collagen triple helix, and the impaired collagen synthesis leads mainly to defective connective tissue. 

---