Phenylalanine biosynthesis and its relationship to accumulation of capsaicinoids during Capsicum chinense fruit development

Activities of phenylalanine (Phe) biosynthetic enzymes chorismate mutase (CM) and arogenate dehydratase (ADT) and of phenylalanine ammonia lyase [PAL, an enzyme that directs Phe towards capsaicinoid (CAP) synthesis] were analyzed during Capsicum chinense Jacq. (habanero pepper) fruit development. A maximum CM activity coincided with a maximum CAP accumulation. However, ADT exhibited two activity peaks, one during the early phase (10 - 17 days post-anthesis, DPA) and another during the late phase (35 - 37 DPA); only the latter coincided with CAP. Interestingly, PAL activity was inversely related to CAP accumulation; lower activities coincided with a maximum CAP content. These results suggest the operation of a control mechanism that coordinated Phe synthesis and its channeling towards CAP synthesis during the course of fruit development.