Abstract
A low molecular weight serine protease from seeds of Citrullus colocynthis was purified to electrophoretic homogeneity with high level of catalytic efficiency (22,945 M−1 S−1). The enzyme was a monomer with molecular mass of 25 kDa estimated by SDS–PAGE. The enzyme was highly active over a pH range of 6.5–9.0 and temperature range of 20–80 °C, with maximum activity at pH 7.5 and at 50 °C. The Km and Kcat were 73 μg/mL and 67/s, respectively. The enzyme was strongly inhibited by PMSF, moderately by soybean trypsin inhibitor, indicating that the enzyme was a serine protease. The enzyme retained 86 and 73% of its activity in the presence of urea and DTT, respectively, and its activity was slightly enhanced in the presence of anionic detergent (SDS). Thus, the enzyme is a novel SDS-stable protease with high catalytic efficiency over wide ranges of pH and temperature which is commercially promising for various industrial applications.
Graphical abstract
Acknowledgement
We are very grateful to Prof. Muhammad Iqbal Chaudry, director of HEJ-Research Institute of Chemistry, University of Karachi for allowing us to use their research facilities.
Disclosure statement
No potential conflict of interest was reported by the authors.