Protease from the sarcocarp of Trichosanthes bracteata

A protease has been purified from sarcocarp of Trichosanthes bracteata (Lam.) Voigt by four steps of chromatography. Its M(r) was estimated by SDS-PAGE to be ca 67,000. The optimum pH of the enzyme was 11 at 35 degrees using casein substrate. The enzyme was strongly inhibited by di-isopropyl fluorophosphate, but not by EDTA and cysteine protease inhibitors. The oxidized insulin B-chain was cleaved at the peptide bonds of Cys7 (SO3H)-Gly8, Glu13-Ala14, Try16-Leu17 by the enzyme for 1 min. The results indicated that the T. bracteata protease is serine protease, similar to cucumisin from the sarcocarp of melon fruit (Cucumis melo L. var. Prince).