Binding and hydrolysis of radiolabeled pheromone and several analogs by male-specific antennal proteins of the mothAntheraea polyphemus

Abstract

Sensory hair proteins from antennae of males of the wild silk moth,Antheraea polyphemus (Lepidoptera, Saturniidae) were incubated with radiolabeled 6E,11Z-hexadecadienyl acetate in the presence of unlabeled pheromone analogs as competitive inhibitors. The two extracellular proteins of importance, a highly active sensillar esterase and an abundant 15,000 mol wt binding protein, interact to degrade labeled pheromone less efficiently in the presence of certain unsaturated acetate analogs of the natural pheromone.

Enzymatic hydrolysis of the acetate (or diazoacetate) was also examined for three pheromone analogs: [11,12-³H₂]-6E,11Z-hexadecadienyl diazoacetate, [11,12-³H₂]-hexadecyl acetate, and [9,10-³H₂]-9Z-tetradecenyl acetate. The former two are poor substrates at concentrations over four orders of magnitude. The 9Z–14:Ac, however, is the best alternative substrate for this in vitro pheromone metabolism system. Unlabeled 9Z–14: Ac is also the best competitive inhibitor of the hydrolysis of labeled 6E, 11Z–16: Ac. Whereas the tritiated natural pheromone shows a flat response (ca. 40% conversion) to increasing concentrations from 3 × 10⁻⁹ to 3 × 10⁻⁶ M, tritiated 9Z–14: Ac is degraded more rapidly at higher concentrations.