| Abstract: | The cell-free synthesis of hyaluronic acid has been demonstrated in extracts of cultured human fibroblasts. Preparations from fibroblasts of normal individuals as well as those from patients with Marfan syndrome incorporate glucuronic acid and N-acetylglucosamine from their UDP derivatives into hyaluronic acid. Extracts from Marfan fibroblasts demonstrate 3 to 10 times more total and specific hyaluronic acid synthetase activity than do preparations from normal fibroblasts. All synthetic activity was found in particulate fractions with the bulk of activity localized in material sedimenting as large membrane fragments. Marfan and normal preparations exhibited similar properties with respect to substrate, cofactor, pH requirements, and heat stability. Neither the Marfan nor normal enzyme systems could be stimulated by exogenous acceptors, nor did either preparation contain a soluble factor which stimulated or inhibited the enzymic activity of the other. The genetic defect in Marfan syndrome appears to result in increased activity of hyaluronic acid synthetase without demonstrable changes in properties of the particulate enzymes involved. |
