ABSTRACT
Natural terpenoids have elaborate structures and various bioactivities, making difficult their synthesis and labeling with isotopes. We report here the enzymatic total synthesis of plant hormone gibberellins (GAs) with recombinant biosynthetic enzymes from stable isotope-labeled acetate. Mevalonate (MVA) is a key intermediate for the terpenoid biosynthetic pathway. ¹³C-MVA was synthesized from ¹³C-acetate via acetyl-CoA, using four enzymes or fermentation with a MVA-secreted yeast. The diterpene hydrocarbon, ent-kaurene, was synthesized from ¹³C-acetate and ¹³C-MVA with ten and six recombinant enzymes in one test tube, respectively. Four recombinant enzymes, P450 monooxygenases and soluble dioxygenases involved in the GA4 biosynthesis from ent-kaurene via GA12 were prepared in yeast and Escherichia coli. All intermediates and the final product GA4 were uniformly labeled with ¹³C without dilution by natural abundance when [U-¹³C2] acetate was used. The ¹³C-NMR and MS data for [U-¹³C20] ent-kaurene confirmed ¹³C-¹³C coupling, and no dilution with the ¹²C atom was observed.
