The production and secretion of procollagen peptidase by human fibroblasts in culture

Procollagen peptidase, the enzyme that converts procollagen to collagen prior to fiber formation, is produced by human fibroblasts in culture. Almost all of the enzymntic activity was found in the medium while little activity was detected with the cells. Activity was not significant during the rapid proliferative phase of cell growth. However, as the cells reached saturation density procollagen pcptidase activity increased rapidly. The accumulation of enzyme in the medium of cultured fibroblasts is consistent with an extracellular conversion of procollagen to collagen, since the proposed functions of the extra aminoterminal peptides of procollagen are to prevent intracellular fibrogenesis and to facilitate secretion.