Studies on the biosynthesis of collagen. II. The conversion of 14C-L-proline to 14C-hydroxyproline by fowl osteoblasts in tissue culture

1. Fowl osteoblasts grown in bulk tissue cultures in the presence of (14)C-(L)-proline incorporated this amino acid into peptide linkage. A significant amount of the incorporated radioactivity was found in the hydroxyproline, glutamic acid, and aspartic acid fractions of the cultures. 2. The rate of formation of protein-bound (14)C-hydroxyproline from (14)C-(L)-proline was maximal in cultures grown for 15 hours and fell exponentially with the increasing age of the cultures. 3. (14)C-(L)-glutamic acid was incorporated by the osteoblast cultures, but no significant amount was converted to hydroxyproline.