title: The hunt for 8-oxoguanine deaminase.
abstract: An enzyme from Pseudomonas aeruginosa, Pa0142 (gi|9945972), that is able to catalyze the deamination of 8-oxoguanine (8-oxoG) to uric acid has been identified for the first time. 8-Oxoguanine is formed by the oxidation of guanine residues within DNA by reactive oxygen species, and this lesion results in G:C to T:A transversions. The value of k(cat)/K(m) for the deamination of 8-oxoG by Pa0142 at pH 8.0 and 30 degrees C is 2.0 x 10(4) M(-1) s(-1). This enzyme can also catalyze the deamination of isocystosine and guanine at rates that are approximately an order of magnitude lower. The three-dimensional structure of a homologous enzyme (gi|44264246) from the Sargasso Sea has been determined by X-ray diffraction methods to a resolution of 2.2 A (PDB entry). The enzyme folds as a (beta/alpha)(8) barrel and is a member of the amidohydrolase superfamily with a single zinc in the active site. This enzyme catalyzes the deamination of 8-oxoG with a k(cat)/K(m) value of 2.7 x 10(5) M(-1) s(-1). Computational docking of potential high-energy intermediates for the deamination reaction to the X-ray crystal structure suggests that active-site binding of 8-oxoG is facilitated by hydrogen-bond interactions from a conserved glutamine that follows beta-strand 1 with the carbonyl group at C6, a conserved tyrosine that follows beta-strand 2 with N7, and a conserved cysteine residue that follows beta-strand 4 with the carbonyl group at C8. A bioinformatic analysis of available protein sequences suggests that approximately 200 other bacteria possess an enzyme capable of catalyzing the deamination of 8-oxoG.
authors.affiliation: Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Hall
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Fedorov
authors.forename: Ricardo
authors.initials: R
authors.lastname: Marti-Arbona
authors.forename: Elena V
authors.initials: EV
authors.lastname: Fedorov
authors.forename: Peter
authors.initials: P
authors.lastname: Kolb
authors.forename: J Michael
authors.initials: JM
authors.lastname: Sauder
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Burley
authors.forename: Brian K
authors.initials: BK
authors.lastname: Shoichet
authors.forename: Steven C
authors.initials: SC
authors.lastname: Almo
authors.forename: Frank M
authors.initials: FM
authors.lastname: Raushel
mesh_terms: D020134:Catalytic Domain; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000201:enzymology; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D006148:Guanine Deaminase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D014527:Uric Acid / Q000378:metabolism
chemical_list: D014527:Uric Acid; C024829:8-hydroxyguanine; D006147:Guanine; D006148:Guanine Deaminase