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The mechanism of oxygen activation by Pea Seedling Amine Oxidase
Author(s) -
Sommer Dayn Joseph,
Choi Eunah,
Bitsimis Alexandra,
Chow Courtney,
Mills Stephen
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.756.23
Subject(s) - chemistry , electron transfer , active site , catalysis , kinetics , amine oxidase , cofactor , reaction mechanism , oxidase test , redox , amine gas treating , oxygen , photochemistry , stereochemistry , enzyme , inorganic chemistry , organic chemistry , physics , quantum mechanics
Copper Amine Oxidases (CAOs) are a large family of enzymes that catalyze the oxidation of primary amines to aldehydes and ammonia, with concomitant reduction of O 2 to H 2 O 2 . These enzymes utilize two cofactors to accomplish this reduction, topaquinone (TPQ) and a Cu(II) ion. Catalysis occurs through ping‐pong kinetics in two half‐reactions, a reductive half‐reaction and an oxidative half‐reaction. Two mechanisms have been proposed for the oxidative half‐reaction. In one mechanism (indirect electron transfer), an electron is initially transferred from the TPQ cofactor to Cu(II), forming Cu(I). Molecular oxygen can then bind reversibly to Cu(I) for catalysis to proceed. In a second mechanism (direct electron transfer), the TPQ cofactor transfers an electron directly to a prebound oxygen molecule, with no reduction of the Cu(II). To study which of the proposed mechanisms PSAO uses, the active site Cu(II) was replaced with Co(II) and the kinetics of CoPSAO were studied. Since Co(II) cannot be reduced to Co(I) in a protein, the indirect electron transfer mechanism is blocked. If PSAO uses the indirect mechanism, it will not be active with Co(II) in the active site. If PSAO is active with Co(II) in the active site, then it likely uses the direct mechanism. CoPSAO showed a 95% decrease in k cat , indicating a strong preference for the indirect electron transfer mechanism. This work was supported by the University of San Diego.