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Bacteria can produce gibberellin plant hormones. While the bacterial biosynthetic pathway is similar to that of plants, the individual enzymes are very distantly related and arose via convergent evolution. The cytochromes P450 (CYPs) that catalyze the multi-step oxidation of the alkane precursor ent -kaurene ( 1 ) to ent -kauren-19-oic acid ( 5 ), are called ent -kaurene oxidases (KOs), and in plants are from the CYP701 family, and share less than 19% amino acid sequence identity with those from bacteria, which are from the phylogenetically distinct CYP117 family. Here the reaction series catalyzed by CYP117 was examined by 18 O 2 labeling experiments, the results indicate successive hydroxylation of 1 to ent -kauren-19-ol ( 2 ) and then ent -kauren-19,19-diol ( 3 ) and most likely an intervening dehydration to ent -kauren-19-al ( 4 ) prior to the concluding hydroxylation to 5 . Accordingly, the bacterial and plant KOs converged on catalysis of the same series of reactions, despite their independent evolutionary origin. 

Biosynthesis of the gibberellin (GA) plant hormones evolved independently in plants and microbes, but the pathways proceed by similar transformations. The combined demethylation and γ‐lactone ring forming transformation is of significant mechanistic interest, yet remains unclear. The relevant CYP112 from bacteria was probed by activity assays and¹⁸O₂‐labeling experiments. Notably, the ability oftert‐butyl hydroperoxide to drive this transformation indicates use of the ferryl‐oxo (Compound I) from the CYP catalytic cycle for this reaction. Together with the confirmed loss of C20 as CO₂, this necessitates two catalytic cycles for carbon–carbon bond scission and γ‐lactone formation. The ability of CYP112 to hydroxylate the δ‐lactone form of GA₁₅, shown by the labeling studies, is consistent with the implied use of a further oxygenated heterocycle in the final conversion of GA₂₄into GA₉, with the partial labeling of GA₉, thus demonstrating that CYP112 partitions its reactants between two diverging mechanisms.