Cucumisin-like protease from the latex of Euphorbia supina

A protease has been purified From the latex of Euphorbia supina Rafin by two steps of chromatography. The M-t, was estimated by SDS-PAGE to be 80 kDa. Its activity was inhibited strongly by diisopropyl fluorophosphate: but not by EDTA, pepstatin, or cysteine protease inhibitors, indicating that the enzyme is a serine protease. The specificity of the protease is broad, but the preferential cleavage sites were C-terminal sites of hydrophobic amino acid residues. The N-terminal sequence of the first fifteen residues was determined and six of the residues match those in cucumisin [EC 3.4.21.25], a protease from the sarcocarp of melon fruit (Cucumis melo L. var. Prince). The results indicate that the E. supina Protease is a cucumisin-like serine protease. (C) 2000 Elsevier Science Ltd. All rights reserved.