ATR-FTIR study of the protonation states of the Glu residue in the multicopper oxidases, CueO and bilirubin oxidase |
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Authors: | Masayo Iwaki Kunishige Kataoka Ryosuke Sugiyama Takeshi Sakurai |
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Affiliation: | a Frontier Research Center, Toyota Central R&D Laboratories Inc., Nagakute, Aichi 480-1192, Japan b Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan |
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Abstract: | Redox-induced protonation state changes of the Glu residue in the multicopper oxidases, CueO and bilirubin oxidase (BO), were studied by attenuated total reflectance-Fourier transform infrared spectroscopy. By monitoring IR bands of the carboxylic acid CO stretch in the wild-type and Glu-to-Gln mutant enzymes the Glu506 of CueO (Glu463 of BO) was found to be unprotonated in the oxidised and protonated in the reduced forms. The results provided direct evidence for proton uptake by the Glu, suggesting it plays a key role in the proton donation to the activated oxygen species in the catalytic cycle. |
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Keywords: | ATR-FTIR, attenuated total reflectance-Fourier transform infrared BO, bilirubin oxidase |
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