STEROL-METABOLISM IN THE TOBACCO HORNWORM, MANDUCA-SEXTA - A REVIEW

A number of intermediates involved in the dealkylation and conversion of the major C-28 and C-29 phytosterols to cholesterol in insects were first isolated and identified in studies with the tobacco hornworm, M anduca sexta, carried out in our laboratory. We also investigated the effects of a variety of known sterol metabolism inhibitors in Manduca, particularly those affecting the Delta(24)-sterol reductase enzyme, a nd synthesized and tested a number of new inhibitors as well. In-depth studies of ecdysteroids in Manduca during embryogenesis and during pu pal-adult development provided new information on molting hormone cont ent, biosynthesis, and metabolism. In addition, this insect has been u tilized in the study of three specific enzyme systems of ecdysteroid m etabolism, namely 20-monooxygenase, 3-epimerase, and phosphotransferas e, which are critical to activation and deactivation of molting hormon es in insects.