The processing of types I and III
procollagen was studied in skin fibroblast cultures from type VII A and B of the
Ehlers-Danlos syndrome [EDS] and age-matched controls. Synthesis of collagenous
proteins was significantly increased in EDS type VII B, and the activities of prolyl-4-hydroxylase and
galactosylhydroxylysyl glucosyltransferase were slightly increased in these cell lines, reflecting increased biosynthesis of
collagen. The synthesis of collagenous
proteins was close to normal in EDS type VII A cells. The synthesis of
type III procollagen per cell was increased, as also was the ratio of immunoreactive
type III procollagen to total
collagen production. The activity of
type I procollagen amino-terminal
proteinase was decreased in skin fibroblasts of type VII A and normal in those of type VII B relative to cell
protein or
DNA. Type III amino-terminal
proteinase activity was of a level found in normal cells when expressed relative to the
protein or
DNA, and the release of type III amino-terminal propeptides was nevertheless not disturbed in these EDS type VII cell cultures. The results show that only the conversion of
type I procollagen is defective in EDS type VII, and no general defect in
procollagen processing can be found in EDS type VII as has been suggested in the case of
dermatosparaxis, a connective tissue disorder in animals caused by disturbed
procollagen conversion.