JBIC Journal of Biological Inorganic Chemistry

, Volume 24, Issue 1, pp 31–37 | Cite as

Co(II) is not oxidized during turnover in the copper amine oxidase from Hansenula polymorpha

  • Stephen A. MillsEmail author
  • Kiera E. Gazica
  • David L. Tierney
Original Paper


Co(II) substitution into the copper amine oxidases (CAOs) has been an effective tool for evaluating the mechanism of oxygen reduction in these enzymes. However, formation of hydrogen peroxide during turnover raises questions about the relevant oxidation state of the cobalt in these enzymes and, therefore, the interpretation of the activity of the metal-substituted enzyme with respect to its mechanism of action. In this study, Co(II) was incorporated into the CAO from Hansenula polymorpha (HPAO). The effect of hydrogen peroxide on the catalytic activity of cobalt-substituted HPAO was evaluated. Hydrogen peroxide, either generated during turnover or added exogenously, caused a decrease in the activity of the enzyme but did not oxidize Co(II) to Co(III). These results are in strong contrast with results from the CAO from Arthrobacter globiformis (AGAO), where hydrogen peroxide causes an increase in the activity of the enzyme as the Co(II) is oxidized to Co(III). The results of this study with HPAO support previous reports that have shown that this enzyme acts by transferring an electron directly from the reduced TPQ cofactor to dioxygen rather than passing the electron through the bound metal ion. Furthermore, these results provide additional evidence to support the idea that different CAOs use different mechanisms for catalysis.


Amine oxidase (copper containing) TOPA quinone Metal substitution Kinetics Catalysis 



Arthrobacter globiformis amine oxidase


Copper amine oxidase


Cobalt-substituted HPAO


Copper-depleted HPAO


Electron paramagnetic resonance


Hansenula polymorpha amine oxidase


Inductively coupled plasma-atomic emission spectroscopy


3-(N-Morpholino)-propanesulfonic acid




Pea seedling amine oxidase


2,4,5-Trihydroxyphenylalanyl quinone



SAM acknowledges the other Xavier students who work in the lab. SAM and KEG acknowledge the Xavier University Office of Undergraduate Research for support.


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Copyright information

© SBIC 2018

Authors and Affiliations

  • Stephen A. Mills
    • 1
    Email author
  • Kiera E. Gazica
    • 1
  • David L. Tierney
    • 2
  1. 1.Department of ChemistryXavier UniversityCincinnatiUSA
  2. 2.Department of Chemistry and BiochemistryMiami UniversityOxfordUSA

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