Hydrogen Tunneling in Peptidylglycine α-Hydroxylating Monooxygenase

The temperature dependence of the primary and secondary intrinsic isotope effects for the C-H bond cleavage catalyzed by peptidylglycine alpha-hydroxylating monooxygenase has been determined. Analysis of the magnitude and Arrhenius behavior of the intrinsic isotope effects provides strong evidence for the use of tunneling as a primary catalytic strategy for this enzyme. Modeling of the isotope effect data allows for a comparison to the hydrogen transfer catalyzed by soybean lipoxygenase in terms of environmental reorganization energy and frequency of the protein vibration that controls the hydrogen transfer.