title: Enzyme kinetics of an alternative splicing isoform of mitochondrial 8-oxoguanine DNA glycosylase, ogg1-1b, and compared with the nuclear ogg1-1a.
abstract: Eight alternatively spliced isoforms of human 8-oxoguanine DNA glycosylase (OGG1) (OGG1-1a to -1c and -2a to -2e) are registered in the National Center for Biotechnology Information. OGG1(s) in mitochondria have not yet been fully characterized biochemically. In this study, we purified mitochondrial recombinant OGG1-1b protein and compared its activity with nuclear OGG1-1a protein. The reaction rate constant (kg ) of the 7,8-dihydro-8-oxoguanine (8-oxoG) glycosylase activity of OGG1-1b was 8-oxoG:C >> 8-oxoG:T >> 8-oxoG:G > 8-oxoG:A (7.96, 0.805, 0.070, and 0.015 min(-1) , respectively) and that of the N-glycosylase/DNA lyase activity (kgl ) of OGG1-1b was 8-oxoG:C > 8-oxoG:T ≃8-oxoG:G >> 8-oxoG:A (0.286, 0.079, 0.040, and negligible min(-1) , respectively). These reaction rate constants were similar to those of OGG1-1a except for kgl against 8-oxoG:A. APEX nuclease 1 was required to promote DNA strand breakage by OGG1-1b. These results suggest that OGG1-1b is associated with 8-oxoG cleavage in human mitochondria and that the mechanism of this repair is similar to that of nuclear OGG1-1a.
authors.affiliation: Functional Genomics Laboratory, School of Science and Engineering, Aoyama Gakuin University, Sagamihara, Kanagawa, 252-5258, Japan. chiefurihata@gmail.com.
authors.forename: Akira
authors.initials: A
authors.lastname: Ogawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Watanabe
authors.forename: Sayaka
authors.initials: S
authors.lastname: Shoji
authors.forename: Chie
authors.initials: C
authors.lastname: Furihata
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human
keywords: Enzyme Activity; Mitochondrial OGG1-1b; Multiple-turnover Condition; Nuclear OGG1-1a; Single-turnover Condition