Purification and Characterization of an Esterase from <Emphasis Type="Italic">Acinetobacter lwoffii</Emphasis> I6C-1

EstA was purified from the supernatant by A. lwoffii 16C-1. Its molecular mass was determined to be 45 kDa, and the optimal activity occurred when the pH level was 8.0 at a temperature of 37°C. The activation energies for the hydrolysis of p-nitrophenyl butyrate was determined to be 11.25 kcal/mol in the temperature range of 10–37°C. The enzyme was unstable at temperatures higher than 50°C. The Michaelis constant (K _m ) and V _max for p-nitrophenyl butyrate were 11 μM and 131.6 μM min⁻¹ mg of protein-1, respectively. The enzyme was strongly inhibited by Hg²⁻, Ca²⁺, Mg²⁺, Fe²⁺, Cu²⁺, Zn²⁺, Mn²⁺, Co²⁺, ethylemediaminetetraacetic acid (EDTA), phenylmethylsulfonyl fluoride (PMSF), and diisopropyl fluorophosphate (DFP). Received: 20 August 2001 / Accepted: 20 September 2001