title: Purification and some properties of wild-type and N-terminal-truncated ethanolamine ammonia-lyase of Escherichia coli.
abstract: The methods of homologous high-level expression and simple large-scale purification for coenzyme B(12)-dependent ethanolamine ammonia-lyase of Escherichia coli were developed. The eutB and eutC genes in the eut operon encoded the large and small subunits of the enzyme, respectively. The enzyme existed as the heterododecamer alpha(6)beta(6). Upon active-site titration with adeninylpentylcobalamin, a strong competitive inhibitor for coenzyme B(12), the binding of 1 mol of the inhibitor per mol of the alphabeta unit caused complete inhibition of enzyme, in consistent with its subunit structure. EPR spectra indicated the formation of substrate-derived radicals during catalysis and the binding of cobalamin in the base-on mode, i.e. with 5,6-dimethylbenzimidazole coordinating to the cobalt atom. The purified wild-type enzyme underwent aggregation and inactivation at high concentrations. Limited proteolysis with trypsin indicated that the N-terminal region is not essential for catalysis. His-tagged truncated enzymes were similar to the wild-type enzyme in catalytic properties, but more resistant to p-chloromercuribenzoate than the wild-type enzyme. A truncated enzyme was highly soluble even in the absence of detergent and resistant to aggregation and oxidative inactivation at high concentrations, indicating that a short N-terminal sequence is sufficient to change the solubility and stability of the enzyme.
authors.affiliation: Department of Bioscience and Biotechnology, Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.
authors.forename: Keita
authors.initials: K
authors.lastname: Akita
authors.forename: Naoki
authors.initials: N
authors.lastname: Hieda
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Baba
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kawaguchi
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Sakamoto
authors.forename: Yuka
authors.initials: Y
authors.lastname: Nakanishi
authors.forename: Mamoru
authors.initials: M
authors.lastname: Yamanishi
authors.forename: Koichi
authors.initials: K
authors.lastname: Mori
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Toraya
mesh_terms: D002384:Catalysis; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology*; D004981:Ethanolamine Ammonia-Lyase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012995:Solubility
chemical_list: D011994:Recombinant Proteins; D004981:Ethanolamine Ammonia-Lyase