The production and properties of a tissue plasminogen activator from normal epithelial cells grown in microcarrier culture.

A plasminogen activator with different biochemical and physical properties to the one obtained from Bowes melanoma cells has been isolated from a normal epithelial cell line derived from guinea-pig keratocytes (GPK). Cell growth and enzyme production is carried out in microcarrier cultures using up to 15 g Cytodex 3 per litre. Cells are maintained in optimum conditions by the use of a closed perfusion loop and the system has been scaled up to 20 litres. Initially enzyme production was in serum-free medium following a growth phase in serum supplemented medium. However, the discovery that the cells produce the enzyme mainly during the replicative phase has led to investigating the use of serum-substitutes and growth factors on cell growth and enzyme production. The aim is to harvest the enzyme after the growth phase which precludes the use of high (greater than 1%) serum concentrations. The biochemical and biophysical properties of the enzyme are described.