Experimental and computational evidence of metal-O2 activation and rate-limiting proton-coupled electron transfer in a copper amine oxidase

Yi Liu, Arnab Mukherjee, Nadav Nahumi, Mehmet Ozbil, Doreen Brown, Alfredo M. Angeles-Boza, David M. Dooley, Rajeev Prabhakar, Justine P. Roth

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The mechanism of O2 reduction by copper amine oxidase from Arthrobacter globiformus (AGAO) is analyzed in relation to the cobalt-substituted protein. The enzyme utilizes a tyrosine-derived topaquinone cofactor to oxidize primary amines and reduce O2 to H 2O2. Steady-state kinetics indicate that amine-reduced CuAGAO is reoxidized by O2 >103 times faster than the CoAGAO analogue. Complementary spectroscopic studies reveal that the difference in the second order rate constant, kcat/KM(O2), arises from the more negative redox potential of CoIII/II in relation to CuII/I. Indistinguishable competitive oxygen-18 kinetic isotope effects are observed for the two enzymes and modeled computationally using a calibrated density functional theory method. The results are consistent with a mechanism where an end-on (η1)-metal bound superoxide is reduced to an η1-hydroperoxide in the rate-limiting step.

Original languageEnglish (US)
Pages (from-to)218-229
Number of pages12
JournalJournal of Physical Chemistry B
Volume117
Issue number1
DOIs
StatePublished - Jan 10 2013

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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