Partial characterization of acid protease from Galactites tomentosa flowers

A plant aspartic protease from Galactites tomentosa Moench was purified 15,47 fold by salt precipitation then by size-exclusion chromatography.. The enzyme is an acid protease with optimum pH of 4. The optimal temperature for enzyme activity was 40°C and the half-life at 60°C was 21,6 min. The activity versus of the substrate concentration gave a hyperbolic curve, indicating a Michaelis kinetics. The KM calculated from Lineweaver–Burk plot is 3,47g/l when casein was used as substrate. The enzyme inhibition of 100% by pepstatin and on non-inhibition by EDTA and iodoacetamide proved it to be an aspartate protease. SDS–PAGE plus casein showed a single active zone and indicated an estimated molecular mass of 45 kDa.