Artocarpus integer leaf protease: Purification and characterisation

The presence of a protease in Artocarpus integer leaves, which are traditionally used as a meat tenderiser, was verified by the presence of a band at 69 kDa, using caseinolytic zymography. Purification by temperature phase partitioning with Triton X-114, ammonium sulphate precipitation and gel filtration chromatography yielded a preparation with a 12-fold increase in enzyme purity and a final specific activity of 76.67 U/mg. The cysteinic nature of this enzyme was confirmed through inhibition of enzyme activity by E-64 and iodoacetamide and enhancement of activity by cysteine and 2-mercaptoethanol. The protease retained 70% of its activity over a broad pH range (pH 6–12), with optimal activity recorded at pH 10 and 40 °C. The enzyme was stable at temperatures up to 70 °C, with 80% of its activity intact. Addition of 5 mM Ca2+ stimulated enzyme activity and a kinetic study of the enzyme yielded Km and Vmax values of 0.304 mg/mL and 0.735 mg/mL/min, respectively.