title: Molecular cloning and characterization of an NADPH quinone oxidoreductase from Kluyveromyces marxianus.
abstract: NAD(P)H quinone oxidoreductase is a ubiquitous enzyme that is known to directly reduce quinone substrates to hydroquinones by a two-electron reaction. We report the identification of NADPH quinone oxidoreductase from Kluyveromyces marxianus (KmQOR), which reduces quinone substrates directly to hydroquinones. The KmQOR gene was sequenced, expressed in Escherichia coli, purified, and characterized. The open-reading frame of the KmQOR gene consists of 1143 nucleotides, encoding a 380 amino acid polypeptide. The nucleotide sequence of the KmQOR gene was assigned to EMBL under accession number AY040868. The M(r) that was determined by SDS-PAGE for the protein subunit was about 42 kDa, and the molecular mass of the native KmQOR was 84 kDa, as determined by column calibration, indicating that the native protein is a homodimer. The KmQOR protein efficiently reduced 1,4-benzoquinone, whereas no activities were found for menadiones and methoxyquinones. These observations, and the result of an extended sequence analysis of known NADPH quinone oxidoreductase, suggest that KmQOR possesses a different action mechanism.
authors.affiliation: Biomedical Research Center, Korea Institute of Science and Technology, Cheongryang P.O. Box 131, Seoul 130-650, Korea. yshan2@kist.re.kr
authors.forename: Wook Hyun
authors.initials: WH
authors.lastname: Kim
authors.forename: Ji Hyung
authors.initials: JH
authors.lastname: Chung
authors.forename: Jung Ho
authors.initials: JH
authors.lastname: Back
authors.forename: Juhyun
authors.initials: J
authors.lastname: Choi
authors.forename: Joo Hwan
authors.initials: JH
authors.lastname: Cha
authors.forename: Hun Yeoung
authors.initials: HY
authors.lastname: Koh
authors.forename: Ye Sun
authors.initials: YS
authors.lastname: Han
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D007700:Kinetics; D007716:Kluyveromyces / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D016660:NAD(P)H Dehydrogenase (Quinone)