Mechanistic Investigation of a Non-Heme Iron Enzyme Catalyzed Epoxidation in (-)-4'-Methoxycyclopenin Biosynthesis

摘要

Mechanisms have been proposed for α-KG-dependent non-heme iron enzyme catalyzed oxygen atom insertion into an olefinic moiety in various natural products, but they have not been examined in detail. Using a combination of methods including transient kinetics, Moessbauer spectroscopy, and mass spectrometry, we demonstrate that AsqJ-catalyzed (-)-4'-methoxy-cyclopenin formation uses a high-spin Fe(Ⅳ)-oxo intermediate to carry out epoxidation. Furthermore, product analysis on ~(16)O/~(18)O isotope incorporation from the reactions using the native substrate, 4'-methoxy-dehydrocyclopeptin, and a mechanistic probe, dehydro-cydopeptin, reveals evidence supporting oxo↔hydroxo tautomerism of the Fe(Ⅳ)-oxo spedes in the non-heme iron enzyme catalysis.