Cytochrome P450-enzymes involved in the biosynthesis of mono- and sesquiterpenes

Terpenoids form the largest group of plant specialized metabolites and exhibit essential functions in plant metabolism, propagation and defence. Since several mono- and sesquiterpenoids, like artemisinin, menthol and nootkatone, have proven beneficial for mankind, they also possess high socio-economic value. The general mechanisms of terpene biosynthesis are understood and enzymes catalysing the formation of the isoprenoid basic carbon skeletons have been described frequently. In the subsequent pathway steps, it is mainly cytochromes P450 that catalyse the decoration of these basic skeletons and thereby contribute significantly to the structural diversity observed. Structure-function relationship, even though discussed intensively, is poorly understood for this enzyme family; even with the phylogenic relationship well established identification of the functionality of the single enzymes is challenging, and, so far, only a few have been characterized. This review provides an overview over cytochromes P450 participating in the biosynthesis of mono- and sesquiterpenes. Only enzymes that have been described thoroughly after purification and heterologous expression are included in this review and their characteristic features are discussed.