Chimeric Terpene Synthases Possessing both Terpene Cyclization and Prenyltransfer Activities

Prenyltransferase (PT) and terpene synthase (TPS) are key enzymes in the formation of the basic carbon skeletons of terpenoids. The PTs determine the prenyl carbon chain length, whereas TPSs generate the structural complexity of the molecular scaffolds, forming various ring structures. Normally, PTs and TPSs are separate, independent enzymes. However, in 2007, a chimeric enzyme, in which the PT was fused with the TPS, was found in a fungus. Recent studies have revealed that such chimeric TPSs are widely distributed in fungi and function in the biosyntheses of various terpene natural products, including sesterterpenes, which are a relatively rare group of terpenoids. This review summarizes the accumulated knowledge of these recently discovered, unique, chimeric TPSs.