REGULATION OF ENZYMATIC-ACTIVITY INVOLVED IN SEX-PHEROMONE PRODUCTIONIN THE HOUSEFLY, MUSCA-DOMESTICA

Ovarian produced ecdysteroids regulate sex pheromone production in the female housefly, inducing the synthesis of (Z)-9-tricosene (Z9-23:Hy) , cis-9,10-epoxytricosane, (Z)-14-tricosen-10-one and methylalkanes. E xperiments were performed to gain a detailed understanding of the proc esses affected by 20-hydroxyecdysone (20-HE) that result in sex pherom one production as the female becomes reproductively mature. A novel mi crosomal fatty acid synthetase (FAS) is present in the epidermal tissu e and plays a role in producing the methyl-branched fatty acid precurs ors to the methylalkanes. This FAS is released from the microsomes in the presence of 3 M KCl. A major enzyme activity influenced by 20-HE i s the fatty acyl-CoA elongation system. A shift in the chain length sp ecificity of the products of the elongation system causes the change i n the chain lengths of the alkenes produced to switch from C-27 and lo nger in the previtellogenic female to C-23 in the mature female. Data is presented indicating that it is the condensation activity of the el ongation system that is affected. Z9-23:Hy arises from a 24 carbon acy l group which is reduced to an aldehyde, and then converted to the hyd rocarbon. Data is presented demonstrating that it is the fatty acyl-Co A derivative and not the free fatty acid that is the substrate. There does not appear to be a chain length specificity which regulates the c onversion of fatty acyl-CoAs to hydrocarbons as both 24 and 28 carbon fatty acyl-CoAs are converted to hydrocarbon by both males and females of all ages.