Substrate transfer in carotene biosynthesis in Phycomyces

Lycopene cyclization to gamma-carotene and then to beta-carotene is partially blocked in Phycomyces by the presence of car R mutations in heterokaryosis or by the addition of 2-(4-chlorophenyl)thiotriethylamine . HCl to the medium. We have quantitatively determined the carotenes synthesized by Phycomyces under conditions of partially blocked cyclization and in the presence of either car A mutations in heterokaryosis or polyoxyethylenesorbitan monooleate (Tween-80) in the medium. We conclude that transfer of intermediate substrates between the enzyme aggregates involved in carotenogenesis does occur in the wild type but not in heterokaryons for car A mutations, and is facilitated by Tween-80.