Purification and Characterization of Alkaline Protease Isolated from Cotton (Gossypium hirsutum) Seeds

Proteases are widely utilized both in physiological and commercial fields such as medicine, food, detergent, and leather. Plant-originated proteases play a significant role in several biomedical fields due to their easy accessibility and activity. Pakistan is an agro-based country and can be an ideal place for the isolation of industrially important proteases from plant sources such as cotton, which is the main crop and frequently available and low cost. Purification of protease was carried out by fractionation with two-fold acetone, ethanol, methanol and various concentrations (40-80%) of ammonium sulphate. The precipitates formed were collected after centrifugation and dialyzed for 24 hours against universal buffer pH 7.0 and was centrifuged in a cooled refrigerated. The dialyzed sample was loaded on Sephadex G–100 gel column. The fractions of the samples were collected and their absorbance of protein was monitored at 280 nm. The homogeneity of the purified enzyme was checked by SDS gel electrophoresis The purified protease enzyme has optimum activity at 30°C and pH 8.0 when casein was used as substrate. The Km and Vmax values of purified cotton seed's alkaline protease activity was recorded as 0.03M and 17 μmol/minute respectively. Protease activity was increased by the addition of cysteine but inhibited by Iodoacetic acid and β-Mercaptoethanol and decreased with some metal ions. These characteristics of the purified enzyme allowed classifying it as a cysteine protease. In conclusion, this study suggests that the alkaline protease enzyme is the best choice for commercial use