. "Catalyzes the head-to-head condensation of two molecules of farnesyl diphosphate (FPP) into the colorless C(30) carotenoid dehydrosqualene (4,4'-diapophytoene). This is the initial step in the biosynthesis of staphyloxanthin, an orange carotenoid present in most staphylococci strains (By similarity)." .