CHARACTERIZATION OF THE ESTERASE ISOZYMES OF IPS-TYPOGRAPHUS (COLEOPTERA, SCOLYTIDAE)

Four esterase isozymes hydrolyzing alpha-naphthyl acetate (alpha-NA) w ere detected screening whole body homogenates of larvae and adults of Ips typographus by electrophoresis. Two of the four isozymes (isozymes 3 and 4) were not detected by alpha-NA staining in the pupal stage, b ut topical application of juvenile hormone III (JH III) on the pupa in duced these isozymes. The JH esterase (JHE) activity on the gel was as sociated with the proteins of isozyme 2. The compounds OTFP, PTFP, and DFP inhibited this catalytic activity of isozyme 2 on the gel at low concentrations, whereas the proteins of isozyme 3 and 4 were affected only at higher concentrations. A quantitative developmental study was performed to characterize which of the esterases hydrolyzed JH III, us ing a putative surrogate substrate for JH (HEXTAT) and alpha-NA. The I -50 of several esterase inhibitors and the IH metabolites were also de fined. All findings supported the results that a protein associated wi th isozyme 2 is catabolizing JH and that isozymes 3 and 4 are the main contributors to the general esterase activity on alpha-NA. The JHE fr om Tenebrio molitor was purified by affinity chromatography. Although the recovery was low an analytical isoelectric focusing gel shelved th at the JHE activity of the purified enzyme T. molitor cochromatographe d at the same pl as the JHE activity of I. typographus. (C) 1997 Wiley -Liss, Inc.