The role of ascorbic acid in the biosynthesis of collagen II. Site and nature of ascorbic acid participation

Abstract

Studies have been conducted on collagen biosynthesis by embryonic chick tibias in tissue culture and on the nature of the action of ascorbic acid in this system. Inhibitors of electron transport and uncouplers of oxidative phosphorylation were found to inhibit the synthesis of peptide-bound hydroxyproline and other proteins to a similar extent. Although depressed DNA and RNA synthesis by the bones is an early effect of ascorbic acid depletion, the effect of ascorbic acid on collagen synthesis did not appear to be on either the stability or synthesis of collagen mRNA. Puromycin was found to inhibit the synthesis of peptide-bound hydroxyproline more than it inhibited the incorporation of proline into protein, indicating that the incorporation of proline into peptide linkage preceded hydroxylation. Simultaneous addition of ascorbic acid and puromycin to bones prelabeled with [ 14C]proline increased the amount of peptide-bound hydroxyproline in the absence of peptide synthesis. These results indicate that ascorbic acid exerts a direct action on collagen synthesis by stimulating the hydroxylation of peptide-bound proline.