Comparison of cysteine proteases of four laticiferous plants and characterization of Euphorbia nivulia Buch.-Ham. latex glycosylated cysteine peptidase

Investigations have been carried out on proteolytic activities of four laticiferous plants, viz. Calotropis procera (Ait.) R. Br. (Ruie), Carica papaya Linn. (Papaya), Euphorbia nivulia Buch.-Ham. (Sabar) and Ficus carica Linn. (Anjir) using Hammerstein grade casein and skimmed milk powder. Ratio of milk clotting to proteolytic activity was highest in the latex sample of C. papaya followed by F. carica, E. nivulia and C. procera. The crude enzyme of Sabar, Ruie, Papaya and Anjir latices exhibit high proteolytic activity with in a pH range from 6.0-7.8, 6.5-8.0, 6.0-7.5 and 6.0-7.0, while maximum milk clotting activity with in a pH range from 6.0-6.5, 6.0-7.0, 6.0-6.5 and 6.5-7.0, respectively. The optimum temperature of proteolytic enzymes of plant latices were recorded over the temperature range 10-80°C at pH 7.0. Whereas, the optimum temperature range of milk clotting protease(s) for milk coagulation was found in between 45-55°C. Proteolytic activity of all latices was inhibited by cysteine protease inhibitors. Thus, cysteine protease is a unique property of all plant latices. This article describes comparative accounts of proteolytic activities of four plants and characterization of glycosylated cysteine protease of E. nivulia latex.