title: Electron spin-echo studies of the composition of the paramagnetic intermediate formed during the deamination of propanolamine by ethanolamine ammonia-lyase, and AdoCbl-dependent enzyme.
abstract: During the deamination of S-2-aminopropanol by the AdoCbl-dependent ethanolamine ammonia-lyase of Clostridia sp., a catalytic intermediate accumulates whose active site contains two paramagnetic species: cob(II)alamin and a free radical derived from the substrate molecule. Spin-echo spectroscopy has revealed that the unpaired electron on the substrate-derived radical is delocalized over a nitrogen atom that from its quadrupole splittings is probably a component of a secondary amide group. Experiments with 15N- and deuterium-labeled propanolamine gave no evidence of an interaction between this unpaired electron and the nitrogen originally attached to the substrate molecule. These results strongly suggest that the substrate-derived radical in this intermediate has already lost its nitrogen, and that this radical is stabilized by delocalization of the unpaired electron onto a nitrogen most likely situated in one of the peptide bonds of the enzyme backbone.
mesh_terms: D000642:Ammonia-Lyases / Q000494:pharmacology*; D003038:Cobamides / Q000494:pharmacology*; D003641:Deamination; D004981:Ethanolamine Ammonia-Lyase / Q000494:pharmacology*; D005609:Free Radicals; D009584:Nitrogen; D011412:Propanolamines; D013057:Spectrum Analysis
chemical_list: D003038:Cobamides; D005609:Free Radicals; D011412:Propanolamines; D000642:Ammonia-Lyases; D004981:Ethanolamine Ammonia-Lyase; C000913:cobamamide; D009584:Nitrogen