title: Identification of the 1,2-propanediol-1-yl radical as an intermediate in adenosylcobalamin-dependent diol dehydratase reaction.
abstract: The reaction catalyzed by adenosylcobalamin-dependent diol dehydratase proceeds by a radical mechanism. A radical pair consisting of the Co(II) of cob(II)alamin and an organic radical intermediate formed during catalysis gives EPR spectra. The high-field doublet and the low-field broad signals arise from the weak interaction of an organic radical with the low-spin Co(II) of cob(II)alamin. To characterize the organic radical intermediate in the diol dehydratase reaction, several deuterated and (13)C-labeled 1,2-propanediols were synthesized, and the EPR spectra observed in the catalysis were measured using them as substrate. The EPR spectra with the substrates deuterated on C1 showed significant line width narrowing of the doublet signal. A distinct change in the hyperfine coupling was seen with [1-(13)C]-1,2-propanediol, but not with the [2-(13)C]-counterpart. Thus, the organic radical intermediate observed by EPR spectroscopy was identified as the 1,2-propanediol-1-yl radical, a C1-centered substrate-derived radical.
authors.affiliation: Department of Bioscience and Biotechnology, Faculty of Engineering, Okayama University, Tsushima-Naka, Okayama 700-8530, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Yamanishi
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Ide
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Murakami
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Toraya
mesh_terms: D001665:Binding Sites; D002247:Carbon Isotopes / Q000378:metabolism; D003038:Cobamides / Q000737:chemistry* / Q000378:metabolism; D041961:Deuterium Exchange Measurement; D004578:Electron Spin Resonance Spectroscopy; D004734:Energy Metabolism; D005609:Free Radicals; D006860:Hydrogen Bonding; D041121:Klebsiella oxytoca / Q000201:enzymology; D008958:Models, Molecular; D011408:Propanediol Dehydratase / Q000737:chemistry* / Q000378:metabolism; D011409:Propylene Glycols / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D002247:Carbon Isotopes; D003038:Cobamides; D005609:Free Radicals; D011409:Propylene Glycols; D011408:Propanediol Dehydratase; C000913:cobamamide