Characterization of General Esterases in Workers of the Eastern Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract

General esterases from eastern subterranean termite, Reticulitermes flavipes (Kollar), workers were examined for activity and were characterized by electrophoretic and biochemical methods. Greater activity was observed toward α-naphthyl substrates when compared Pared with ρ-nitrophenyl substrates. The specific activity of the esterases increased with a corresponding increase in α-naphthyl acetate concentration. Maximal activities were observed with a buffer pH of 7.6 and an incubation temperature of 45c. The calculated Michaelis-Menten constant (Km) was 72.53 µM and the Vmax was 33.77 µM/min/mg of protein. Nondenaturing polyacrylamide gel electrophoresis revealed the presence of seven esterase bands, which were named EI-E7. Bands EI-E4 (slowest gel mobility) were determined to be cholinesterase based on physostigmine inhibition. The remaining three bands were identified as carboxylesterases based on inhibition by paraoxon. The molecular weights of the seven bands ranged from 71.5 to 97.2 kD.