ASSAY-METHODS FOR METHYL FARNESOATE ESTERASES IN CRUSTACEANS

Methyl farnesoate (MF) is a sesquiterpenoid that is synthesized by cru staceans and is structurally similar to the insect juvenile hormones. MF is metabolized to farnesoic acid by carboxylesterases present in cr ustacean tissues. In order to investigate the biological significance of MF metabolism, we have developed two rapid methods for measuring MF esterase activity. The first method is a radiochemical partition assa y that utilizes an authentic substrate. The [H-3]MF partition assay wa s used to evaluate the spectrophotometric esterase substrates methyl 1 -heptylthioacetothioate (HEPTAT) and methyl 1-pentylthioacetothioate ( PENTAT) for use with crude and partially purified samples of MF estera ses from lobster hepatopancreas (midgut gland). The spectrophotometric method is less specific for MF esterases than the partition assay but is less time consuming and nonradioactive, and it provides kinetic in formation. HEPTAT and PENTAT were suitable for rapid screening of chro matographic fractions for MF esterase activity. (C) 1997 Wiley-Liss, I nc.