Purification and properties of an acid protease from human ascitic fluid

An acid protease was isolated from the ascitic fluid of a patient with ovarian cancer. It was purified about 400-fold to homogeneity by ammonium sulfate fractionation, gel filtration on Sephadex G-200 and DEAE-cellulose column chromatography. Its molecular weight was calculated to be 28 000 by gel filtration, and its isoelectric points was found to be pH 4.1. It showed similar activities on acid-denatured bovine serum albumin and on acid-denatured bovine hemoglobin, and its optimal pH for both substrates was 3.0. Sulfhydryl compounds and metal ions had no apparent effects on this enzyme, but pepstatin was strongly inhibitory.