Neutral Sterol Metabolism in Insects I

Since they are unable to biosynthesize sterols, many phytophagous and omnivorous insects satisfy their cholesterol requirement by side chain dealkylation of the C-24 aikyl group of dietary C~ and C29 phytosterols. However, not all insects that can dealkylate the phytosterol side chain produce cholesterol. In addition, certain insects, e.g., some Hymenoptera, Hemiptera, and Diptera, are unable to dealkylate the sterol side chain. Although Cz7 ecdysteroids {molting hormones), which are biosynthesized from cholesterol, are the major ecdysteroids in most insects, many of those species that are unable to deaikylate phytosterols utilize campesterol as a precursor for the C2s ecdysteroid makisterone A. The considerable diversity of steroid utilization between certain insect species makes it difficult to generalize about insect steroid biochemistry. The ability to disrupt certain unique aspects of steroid utilization and metabolism in insects might be exploited for developing new insect control technology. Lipids 26, 614-618 (1991).