Molecular properties of the product radical in adenosylcobalamin-dependent ethanolamine deaminase

The adenosylcobalamin coenzyme-dependent ethanolamine deaminase from Salmonella typhimurium catalyzes the deamination of aminoethanol to ethanol and ammonia. The product radical observed during steady-state turnover of substrate aminoethanol has been characterized by electron paramagnetic resonance technique. This study explores the conformational dependent hyperfine coupling constants and energetics of the possible product radical intermediates by means of density functional theory based calculations; the results are compared with experimental ones derived from EPR spectra simulations. We have obtained sets of possible conformational structures of the observed product radical indicating that the radical trapped during the catalysis of ethanolamine deaminase corresponds to an activated energy state facilitating the subsequent hydrogen atom abstraction from the inert 5′-methyl group of deoxyadenosine.