Cellular and Molecular Life Sciences

, Volume 66, Issue 9, pp 1570–1579 | Cite as

Structure/function analysis of a critical disulfide bond in the active site of l-xylulose reductase

  • H.-T. Zhao
  • S. Endo
  • S. Ishikura
  • R. Chung
  • P. J. Hogg
  • A. Hara
  • O. El-Kabbani
Research Article

Abstract.

l-Xylulose reductase (XR) is involved in water re-absorption and cellular osmoregulation. The crystal structure of human XR complemented with site-directed mutagenesis (Cys138Ala) indicated that the disulfide bond in the active site between Cys138 and Cys150 is unstable and may affect the reactivity of the enzyme. The effects of reducing agents on the activities of the wild-type and mutant enzymes indicated the reversibility of disulfide-bond formation, which resulted in three-fold decrease in catalytic efficiency. Furthermore, the addition of cysteine (>2 mM) inactivated human XR and was accompanied by a 10-fold decrease in catalytic efficiency. TOF-MS analysis of the inactivated enzyme showed the S-cysteinylation of Cys138 in the wild-type and Cys150 in the mutant enzymes. Thus, the action of human XR may be regulated by cellular redox conditions through reversible disulfide-bond formation and by S-cysteinylation.

Keywords.

l-xylulose reductase short-chain dehydrogenase/reductase X-ray crystallography site-directed mutagenesis disulfide bond protein structure enzyme regulation 

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Copyright information

© Birkhäuser Verlag, Basel 2009

Authors and Affiliations

  • H.-T. Zhao
    • 1
  • S. Endo
    • 2
  • S. Ishikura
    • 2
  • R. Chung
    • 1
  • P. J. Hogg
    • 3
    • 4
  • A. Hara
    • 2
  • O. El-Kabbani
    • 1
  1. 1.Medicinal Chemistry and Drug ActionMonash Institute of Pharmaceutical SciencesVictoriaAustralia
  2. 2.Laboratory of BiochemistryGifu Pharmaceutical UniversityGifuJapan
  3. 3.UNSW Cancer Research CentreUniversity of New South WalesSydneyAustralia
  4. 4.Children’s Cancer Institute Australia for Medical ResearchRandwickAustralia

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