The active site of bovine serum amine oxidase

Abstract

Bovine serum amine oxidase (BSAO) is a type II copper-containing protein. The enzyme has a molecular weight of 190000 daltons and 2 gram atoms of copper per mol protein which is composed of two electrophoretically equivalent subunits. Native BSAO exhibits a yellowish pink color by virtue of a broad band around 476 nm (ϵ = 3800) [1]. Replacement of Co(II) [2], Ni(II) and Zn(II) for the inherent Cu(II) which is coordinated by two cis-arranged imidazole nitrogens and two oxygens [3] revealed that the pink color comes from the organic prosthetic group. Electronic, CD and ESR spectra of native and metal substituted BSAO treated with phenylhydrazine suggested that the unknown prosthetic group is located very close to the copper(II) ion, but probably is not directly coordinated to the metal ion. The presence of a metal ion affects sensitively the electronic state of the prosthetic group whose role is considered to bind a substrate and catalyze the subsequent deamination. At the following step, two electrons are passed from the reduced chromophore to molecular oxygen probably through the copper ion. Combined cooperation of the chromophore and copper(II) ion during the whole enzymatic process corresponds to the catalytic roles of a flavin group. We are now working on the prosthetic group to clarify its structure and properties and also on the copper(II) ion in relation to the chromophore.