Ipsdienol is an important pheromone component for pine engraver beetle, Ips pini. Ipsdienol is a ten carbon monoterpenoid secondary alcohol and ipsdienone is the corresponding ketone. We are characterizing the activity of recombinant IDOL DH produced in Sf9 (insect) cells. The enzyme has a high stereospecificity: (-) ipsdienol was found to be a substrate while (+)-ipsdienol was neither a substrate nor inhibitor. Closely related monoterpenoids, such as nerol, geraniol, and citral, were neither substrates nor inhibitors. Smaller compounds, such as 2-propanol, also failed to act as an inhibitor or substrate. This indicates the binding site of this enzyme is highly selective. Failure to act as an inhibitor most likely indicates these compounds bind weakly (-)-Ipsdienol, ipsdienone, ipsenol, and ipsenone are substrates. Interestingly, menthone, a cyclic analog of ipsdienol, was found to have substrate activity. Results from gel permeation chromatography shows the active conformation of IDOL DH is a tetramer. Together these results suggest IDOLDH has a highly specific substrate binding site, and is a key component in pheromone biosynthesis
