Calcium protects pituitary basic fibroblast growth factors from limited proteolysis by co-purifying proteases

Extracts from bovine pituitaries and other tissues contained basic fibroblast growth factor-like peptides of 22–26 kda, co-fractionating with smaller, 16–20 kda bFGFs. Heparin-bound, 22–26 kda bFGFs were converted to smaller, heparin-binding forms by tryptic proteolysis. In solution, 22–26 kda bFGFs were converted to smaller, heparin-binding forms by an activity present in pituitary extracts. Calcium protected higher molecular weight pituitary bFGFs from truncation by the endogenous activity, which was not acid-activated, co-purified with bFGF during heparin-sepharose chromatography, remained operant at high salt concentrations and was inhibited by phenylmethan-sulfonyl fluoride.