Copper Amine Oxidases (CAOs) are a family of enzymes that catalyze the conversion of primary amines to aldehydes and ammonium, while at the same time reducing O2 to H2O2. These enzymes are found in many different organisms such as bacteria, fungi, plants, and animals. Two cofactors are used by CAOs to carry out this reaction: 2,4,5-trihydroxyphenylalanyl quinone (TPQ) and Cu(II). The overall reaction can be divided into a reductive half-reaction and an oxidative half-reaction. The mechanism for the reductive half-reaction is accepted, while the oxidative half-reaction is debated with two proposed mechanisms. This study will examine the role of the metal in the electron transfer from TPQ to oxygen in the oxidative half-reaction of the CAOs. To examine the role of metal in this mechanism, Cu(II) was removed from the active site and replaced with Co(II). After the metal was replaced, the enzymatic activity of the protein was measured. Recent studies have suggested that different CAO homologs may use each of the proposed mechanisms. The purpose of our studies is to gain a better understanding of the oxidative mechanism of a CAO from pea seedlings (PSAO) and from E. coli (ECAO). We are examining the effect of H2O2 on the activity of Co(II)-substituted PSAO and ECAO to determine if Co(II) is oxidized to Co(III), and if Co(III) can support catalysis in these enzymes.

Studies of the oxidative mechanism of the copper amine oxidases

2019 Spring National Meeting

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