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 mechani sms by which a magnetic field can interact with a biological system. T he kinetic parameter V-max/K-m (where K-m is the Michaelis constant) f or the coenzyme B-12-dependent enzyme ethanolamine ammonia lyase was d ecreased 25 percent by a static magnetic field near 0.1 tesla (1000 ga uss) with unlabeled ethanolamine and decreased 60 percent near 0.15 te sla with perdeuterated ethanolamine. This effect is likely caused by a magnetic field-induced change in intersystem crossing rates between t he singlet and triplet spin states in the {cob(II)alamin:5'-deoxyadeno syl radical} spin-correlated radical pair.