Purification and molecular mass determination of P. americana protease (A). The purified enzyme was separated on 12% SDS-PAGE and protein bands were stained with CBBR-250. Lane 1, standard molecular weight markers, Lane 2, crude extract, Lane 3, acetone precipitate, Lane 4, gel filtration fraction. (B) Detection of protease activity of purified enzyme by gel X-ray film contact print method. Fractions from each purification step were resolved on 10% native-PAGE and protease activity isoforms were visualized on X-ray film. Lane 1, crude extract, Lane 2, acetone precipitate, Lane 3, gel filtration fraction.