Document Type : Original Paper

Author

• A. Asoodeh

Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Islamic Republic of Iran

Abstract

The main objective of this study was to purify and characterize an esterase from Shewanella sp F88. The enzyme was purified 41-fold and an overall yield of 21 %, using a two-step procedure, including ammonium sulfate precipitation and Q-sepharore chromatography. Molecular weight of the enzyme was 62.3 kDa according to SDS-PAGE data. The enzyme showed an optimum activity at pH 6.5 and 58 ˚C. Evolution of substrate specificity demonstrated that this thermostable enzyme had the highest activity towards para-nitrophenol acetate (pNPA, C2). Michaelis-Menten constant (K_m) and maximum velocity (V_max) of pNPA-hydrolyzing reaction were 12.6 mM and 550 U.mg^-1, respectively. Enzyme activity was declined in the presence of metal ions (2 and 5 mM), including Fe²⁺, Ca²⁺, Cu²⁺, Zn²⁺, Mg²⁺ and Mn²⁺. The half-lives of purified esterase was 70 and 31 min at 60 °C and 80 °C, respectively. In conclusion, the enzyme is a novel thermostable lipolytic enzyme characterized from Shewanella species.