Vitamin B12 Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin B12, including details on cyanocobalamin, benefits, supplements, deficiency, side-effects, sources.

Magnetic field effect studies indicate reduced geminate recombination of the radical pair in substrate-bound adenosylcobalamin-dependent ethanolamine ammonia lyase.

Jones AR, Hay S, Woodward JR, Scrutton NS

Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK.

The apparent conflict between literature evidence for (i) radical pair (RP) stabilization in adenosylcobalamin (AdoCbl)-dependent enzymes and (ii) the manifestation of magnetic field sensitivity due to appreciable geminate recombination of the RP has been reconciled by pre-steady-state magnetic field effect (MFE) investigations with ethanolamine ammonia lyase (EAL). We have shown previous stopped-flow MFE studies to be insensitive to magnetically induced changes in the net forward rate of C-Co homolytic bond cleavage. Subsequently, we observed a magnetic-dependence in the continuous-wave C-Co photolysis of free AdoCbl in 75% glycerol but have not done so in the thermal homolysis of this bond in the enzyme-bound cofactor in the presence of substrate. Consequently, in the enzyme-bound state, the RP generated upon homolysis appears to be stabilized against the extent of geminate recombination required to observe an MFE. These findings have strong implications for the mechanism of RP stabilization and the unprecedented catalytic power of this important class of cobalamin-dependent enzymes.

Published 12 December 2007 in J Am Chem Soc, 129(50): 15718-27.
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