Magnetic Field Effects on B 12 Ethanolamine Ammonia Lyase: Evidence for a Radical Mechanism

A change in radical pair recombination rates is one of the few mechanisms by which a magnetic field can interact with a biological system. The kinetic parameter V max /K m (where K m is the Michaelis constant) for the coenzyme B 12 -dependent enzyme ethanolamine ammonia lyase was decreased 25 percent by a static magnetic field near 0.1 tesla (1000 gauss) with unlabeled ethanolamine and decreased 60 percent near 0.15 tesla with perdeuterated ethanolamine. This effect is likely caused by a magnetic field-induced change in intersystem crossing rates between the singlet and triplet spin states in the [cob(II)alamin:5′-deoxyadenosyl radical} spin-correlated radical pair.