title: Purification and biochemical properties of SDS-stable low molecular weight alkaline serine protease from Citrullus colocynthis.
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 K(m) and K(cat) 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.
authors.affiliation: a Department of Bioscience , COMSATS Institute of Information Technology Islamabad , Pakistan.|b H.E.J Research Institute of Chemistry , International Centre for Chemical Sciences, University of Karachi , Karachi , Pakistan.
authors.forename: Muhammad Bashir
authors.initials: MB
authors.lastname: Khan
authors.affiliation: c Department of Chemistry , University of Science and Technology , Bannu , Pakistan.
authors.forename: Hidayatullah
authors.initials: H
authors.lastname: Khan
authors.affiliation: a Department of Bioscience , COMSATS Institute of Information Technology Islamabad , Pakistan.
authors.forename: Muhammad Usman
authors.initials: MU
authors.lastname: Shah
authors.affiliation: a Department of Bioscience , COMSATS Institute of Information Technology Islamabad , Pakistan.
authors.forename: Sanaullah
authors.initials: S
authors.lastname: Khan
mesh_terms: D065986:Citrullus colocynthis / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D012639:Seeds / Q000737:chemistry; D057057:Serine Proteases / Q000737:chemistry* / Q000302:isolation & purification; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D057057:Serine Proteases
keywords: Citrullus colocynthis; biochemical characterisation; detergent stability; purification; serine protease; thermostability