INTRACELLULAR SIGNAL-TRANSDUCTION OF PBAN ACTION IN THE SILKWORM, BOMBYX-MORI - INVOLVEMENT OF ACYL COA REDUCTASE

In the silkworm, Bombyx mori, production of the sex pheromone bombykol is regulated by a neurohormone termed PBAN. We have detected the acti vity of acyl CoA reductase in the pheromone gland of B. mori by using palmitoyl CoA as a substrate, The acyl CoA reductase requires NADPH, b ut not NADH, as a proton donor, When the pheromone gland was incubated with the PBAN fragment peptide TKYFSPRLamide, palmitoyl CoA was incor porated and converted into the corresponding C-16 alcohols. Radio HPLC analysis revealed that these C-16 alcohols were hexadecan-1-ol (81.2% ), (Z)-11-hexadecen-1-ol (12.3%), and (E, Z)-10, 12-hexadecadien-1-ol (= bombykol, 6.5%). The production of C-16 alcohols in the pheromone g land was inhibited by the known bombykol biosynthesis inhibitors EDTA, LaCl3, W-7, trifluoperazine, p-nitrophenyl phosphate, NaF and compact in, By contrast, when the pheromone gland homogenate was incubated in the presence of palmitoyl CoA and NADPH, production of C-16 alcohols w as affected by compactin, W-7 and trifluoperazine, but not by EDTA, La Cl3, p-nitrophenyl phosphate and NaF. These results indicate that comp actin, W-7 and trifluoperazine directly suppress the step catalyzed by acyl CoA reductase, whereas EDTA, LaCl3, pNPP, and NaF inhibit bombyk ol production by affecting other biochemical steps in the signal trans duction of PBAN action, The present results also imply that PBAN regul ates the step catalyzed by acyl CoA reductase and that palmitoyl CoA c ould be used as a substrate of the acyl CoA reductase that regulates b ombykol biosynthesis.