Date of Award
Doctor of Philosophy
Biochemistry, Biophysics and Molecular Biology
Reuben J. Peters
Due to their abundance in secondary metabolites, plants are a rich source of chemical diversity. Terpenoids comprise the largest class of natural products, yet many of the biosynthetic pathways leading to their production remain under explored. Using rice as a model system, the biosynthesis of labdane-related class I synthases and P450s was explored through the development of a facile, modular metabolic engineering system. Herein, details of the characterization of the rice class I labdane-related synthase family and CYP76M7 are included. Accordingly, it was found that rice possesses a stemodene synthase, bi-selective syn-labdatriene/ent-sandaracopimaradiene synthase, and a cassadiene C11 hydroxylating P450. Phytochemical analysis of rice extracts revealed the presence of the characterized diterpenes made by class I synthases. Additionally, it was found that the class I synthases exhibit a high degree of plasticity with respect to substrate selection and product outcome, including the ability of OsKSL4 T696I to produce aphidicolene. Furthermore, the first bacterial class I synthases involved in gibberellin production has been identified and characterized. Kaurene oxidase is the first cytochrome P450 involved in the biosynthesis of gibberellin growth hormones. Oxygen labeling experiments revealed this multifunctional P450 undergoes successive hydroxylation reactions with retention of intermediates through a gem-diol to form a carboxylic acid. The studies presented in this thesis detail the development of a metabolic engineering system to investigate terpenoid biosynthesis, the characterization of class I synthases and P450s, and mechanistic investigations of class I synthases and P450s involved in labdane-related biosynthesis.
Morrone, Dana, "On the biosynthesis of labdane-related diterpenoids by class I synthases and P450s: a" (2008). Graduate Theses and Dissertations. 11311.