Approaches to the purification of the juvenile hormone esterase from the cabbage looper,Trichoplusia ni

Several approaches to the purification of juvenile hormone (JH) esterase from second-day last-instar larvae of Trichoplusia ni were taken, including: ammonium sulphate precipitation, polyethylene glycol precipitation, hydrophobic interaction chromatography, anion exchange chromatography, and gel filtration chromatography. The most successful procedure involved a combination of polyethylene glycol precipitation with anion exchange chromatography on DEAE Sephacel which yielded a 134-fold purification of juvenile hormone esterase. When this preparation was subjected to semi-preparative electrophoresis followed by isoelectric focusing on a polyacrylamide slab gel, a single band of apparently homogeneous enzyme was obtained. Juvenile hormone esterase activity was unstable after electrophoresis and isoelectric focusing. The stability of juvenile hormone esterase activity in a water solution is influenced by protein concentration and by agents protecting sulphydryl groups. The results of this study support the hypothesis that a single protein is responsible for the majority of the JH hydrolysis catalyzed by haemolymph from the larvae of T. ni used in this study.