Probing the radical mechanism of galactose oxidase using an ultrafast radical probe

Processing of trans-2-phenylcyclopropylmethanols 5 and 6 by the monocopper/tyrosine radical enzyme galactose oxidase led to mechanism-based inactivation with a partition ratio, (kcat + kinact)/kinact, of approximately 1 and a primary deuterium isotope effect, kinact(H)/kinact(D), of 3.2. The data are consistent with a radical mechanism for galactose oxidase with a short lived ketyl radical anion intermediate.