Characterization of the acetyltransferase used in pheromone biosynthesis in moths: Specificity for the Z isomer in tortricidae

Abstract

Characterization of the acetyltransferase (acetyl-CoA: fatty alcohol acetyltransferase) that catalyzes the conversion of fatty alcohols to acetate esters was carried out in the redbanded leafroller moth, Argyrotaenia velutinana. This enzyme is one of the last enzymes used in the pheromone biosynthetic pathway of many moths. Characterization of the acetyltransferase involved an in vitro enzyme assay using a pheromone gland homogenate. The enzyme found only in the pheromone gland, was active during the photophase and at all adult ages tested (1–5-days-old). The enzyme was derermined to be microsomal and exhibited specificity for the Z isomer of all 12, 14 and 16 carbon monounsaturated fatty alcohol substrates tested. The shape of the kinetic curves for the Z and E isomers of Δ11-tetradecenol were similar for time of incubation, protein and substrate concentration, with the Z isomer always forming 1.5–2 times more product. Substrate competition assays between Z and E11-tetradecenol indicate that one enzyme is involved and it converts the Z isomer to product faster than the E isomer. Substrate preference assays conducted with the enzyme from Choristoneura rosaceana, C. fumiferana and Platynota idaeusalis (all Tortricidae) pheromone glands also indicate specificity for the Z isomer. On the other hand, assays conducted with Trichoplusia ni (Noctuidae) and three strains ( Z, E and hybrid) of Ostrinia nubilalis (Pyralidae) indicate no preferences between the Z and E isomers.