title: An electron paramagnetic resonance study on the mechanism-based inactivation of adenosylcobalamin-dependent diol dehydrase by glycerol and other substrates.
abstract: Adenosylcobalamin-dependent diol dehydrase undergoes mechanism-based inactivation by glycerol or other substrates during catalysis. X-band electron paramagnetic resonance spectra of holoenzyme were measured at -130 degrees C after reaction with such substrates. After short time of incubation, broad signals assigned to low-spin Co(II) of cob(II)alamin and doublet signals assigned to an organic radical intermediate derived from each substrate were observed with 1,2-propanediol, 1,2-ethanediol, glycerol and meso-2,3-butanediol with the magnitude of their exchange interaction (J-value) decreasing in this order. A substrate with the smaller magnitude of exchange interaction between low-spin Co(II) and an organic radical intermediate seems to be an efficient mechanism-based inactivator. Since the magnitude of exchange interaction decreases with the distance between radical species in a radical pair, these results suggest that a stabilizing effect of holoenzyme on radical intermediates during reactions decreases with the distance between Co(II) and a radical.
authors.affiliation: Faculty of Engineering, Okayama University, Japan. toraya@cc.okayama-u.ac.jp
authors.forename: T
authors.initials: T
authors.lastname: Toraya
authors.forename: M
authors.initials: M
authors.lastname: Yamanishi
authors.forename: H
authors.initials: H
authors.lastname: Muguruma
authors.forename: K
authors.initials: K
authors.lastname: Ushio
authors.forename: J
authors.initials: J
authors.lastname: Yamauchi
authors.forename: T
authors.initials: T
authors.lastname: Kawamura
mesh_terms: D001051:Apoenzymes; D003038:Cobamides; D003067:Coenzymes; D003080:Cold Temperature; D004578:Electron Spin Resonance Spectroscopy; D019855:Ethylene Glycol; D005026:Ethylene Glycols / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology*; D007709:Klebsiella / Q000201:enzymology; D011408:Propanediol Dehydratase / Q000037:antagonists & inhibitors* / Q000235:genetics; D011994:Recombinant Proteins
chemical_list: D001051:Apoenzymes; D003038:Cobamides; D003067:Coenzymes; D005026:Ethylene Glycols; D011994:Recombinant Proteins; D011408:Propanediol Dehydratase; C000913:cobamamide; D019855:Ethylene Glycol; D005990:Glycerol