Abstract
The catalytic pathways of soluble methane monooxygenase (sMMO) and cytochrome P450CAM, iron-containing enzymes, are described and compared. Recent extensive density functional
ab initio electronic structure calculations have revealed many similarities in a number of the key catalytic steps, as well as some important differences. A particularly interesting and significant contrast is the role played by the protein in each system. For sMMO, the protein stabilizes various species in the catalytic cycle through a series of carboxylate shifts. This process is adequately described by a relatively compact model of the active site (∼100 atoms), providing a reasonable description of the energetics of hydrogen atom abstraction. For P450CAM, in contrast, the inclusion of the full protein is necessary for an accurate description of the hydrogen atom abstraction.
Using density functional theory, features of the intermediates in the reactions catalyzed be methane monooxygenase and cytochrome P450 can be delineated.