Microsciadin, a New Milk-Clotting Cysteine Protease from an Endemic Species, Euphorbia microsciadia

In the present work, a new branch of biotechnological advantage of the latex of an endemic perennial plant, Euphorbia microsciadia has been introduced. A novel cysteine protease, designated as microsciadin, was purified from the latex of Euphorbia microsciadia by a combination of sequential usage of SPSepharose Fast Flow column in two different pHs and a final gel filtration chromatography. Microsciadin is a monomeric protein with an apparent molecular mass of 60 kDa by SDSPAGE. Although the enzyme was stable over a wide range of pH and temperatures, it displayed the maximum activity at 45 °C and pH of 4.5. The enzyme was strongly inhibited by Iodoacetamide, E64 and Hg2+ ions indicated that it belongs to the cysteine protease family. Furthermore, the enzyme showed suitable stability in the presence of various denaturants and organic solvents. Moreover, primary studies on milk clotting activity of the enzyme revealed its high potential to dairy industry. The acidophilic feature of microsciadin in associated with its high milkclotting activity and remarkable operational stability suggest its potential application in cheese industry, as well as other food and biotechnological fields.