The reductive and oxidative half-reaction and the role of copper ions in plant and mammalian copper-amine oxidase.

In this review, the nature and characteristics of the prosthetic group, the intermediates in the catalytic mechanism, and the role of the copper in plant copper−amine oxidases from pea and lentil seedlings are compared with the corresponding features of mammalian amine oxidase from bovine serum. All these enzymes contain the same organic cofactor derived from the modification of a protected tyrosyl residue. Considering the catalytic mechanism, plant amine oxidase may be referred to as a “protein radical enzyme”, operating through a free radical located on the cofactor. This is in contrast to bovine serum amine oxidase, which forms the free-radical intermediate only to a minor extent in the course of the catalytic cycle. A scheme for the catalytic mechanism is proposed in order to account for this difference.