This CD includes terpenoid cyclases such as pentalenene synthase and aristolochene synthase which, using an all-trans pathway, catalyze the ionization of farnesyl diphosphate, followed by the formation of a macrocyclic intermediate by bond formation between C1 with either C10 (aristolochene synthase) or C11 (pentalenene synthase), resulting in production of tricyclic hydrocarbon pentalenene or bicyclic hydrocarbon aristolochene. As with other enzymes with the 'terpenoid synthase fold', they have two conserved metal binding motifs, proposed to coordinate Mg2+ ion-bridged binding of the diphosphate moiety of FPP to the enzymes. Metal-triggered substrate ionization initiates catalysis, and the alpha-barrel active site serves as a template to channel and stabilize the conformations of reactive carbocation intermediates through a complex cyclization cascade. These enzymes function in the monomeric form and are found in fungi, bacteria and Dictyostelium.
Jiyao W et al.(2023). "The conserved domain database in 2023.",