The substrate specificity of juvenile hormone esterase from Manduca sexta haemolymph

Haemolymph of $\text{Manduca sexta}$ fifth instar larvae contains a high esterase activity capable of hydrolyzing $\text{Hyalophora cecropia}$ C₁₈ juvenile hormone (JH). In an attempt to characterize the substrate specificity of the enzyme (s) involved, dilute haemolymph was incubated $\text{in vitro}$ with a series of JH-analogs. Ethyl esters with or without the 10,11-epoxide group were hydrolyzed readily but isopropyl esters and the (2Z)-isomer of JH were not affected. Indirect evidence was obtained for the hydrolysis of aziridine analogs of JH. Correlations of these results to biological activities are discussed.