Dual role of the carboxyl-terminal region of pig liver l-kynurenine 3-monooxygenase: Mitochondrial-targeting signal and enzymatic activity

Kumiko Hirai, Hidehito Kuroyanagi, Yoshitaka Tatebayashi, Yoshitaka Hayashi, Kanako Hirabayashi-Takahashi, Kuniaki Saito, Seiich Haga, Tomihiko Uemura, Susumu Izumi

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Abstract

l-kynurenine 3-monooxygenase (KMO) is an NAD(P)H-dependent flavin monooxygenase that catalyses the hydroxylation of l-kynurenine to 3-hydroxykynurenine, and is localized as an oligomer in the mitochondrial outer membrane. In the human brain, KMO may play an important role in the formation of two neurotoxins, 3-hydroxykynurenine and quinolinic acid, both of which provoke severe neurodegenerative diseases. In mosquitos, it plays a role in the formation both of eye pigment and of an exflagellation-inducing factor (xanthurenic acid). Here, we present evidence that the C-terminal region of pig liver KMO plays a dual role. First, it is required for the enzymatic activity. Second, it functions as a mitochondrial targeting signal as seen in monoamine oxidase B (MAO B) or outer membrane cytochrome b5. The first role was shown by the comparison of the enzymatic activity of two mutants (C-terminally FLAG-tagged KMO and carboxyl-terminal truncation form, KMOΔC50) with that of the wild-type enzyme expressed in COS-7 cells. The second role was demonstrated with fluorescence microscopy by the comparison of the intracellular localization of the wild-type, three carboxyl-terminal truncated forms (ΔC20, ΔC30 and ΔC50), C-terminally FLAG-tagged wild-type and a mutant KMO, where two arginine residues, Arg461-Arg462, were replaced with Ser residues.

Original languageEnglish
Pages (from-to)639-650
Number of pages12
JournalJournal of Biochemistry
Volume148
Issue number6
DOIs
Publication statusPublished - 01-12-2010

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

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    Hirai, K., Kuroyanagi, H., Tatebayashi, Y., Hayashi, Y., Hirabayashi-Takahashi, K., Saito, K., Haga, S., Uemura, T., & Izumi, S. (2010). Dual role of the carboxyl-terminal region of pig liver l-kynurenine 3-monooxygenase: Mitochondrial-targeting signal and enzymatic activity. Journal of Biochemistry, 148(6), 639-650. https://doi.org/10.1093/jb/mvq099