Copper-containing amine oxidases are found in all the major kingdoms of life. They catalyse the oxidation of organic amines in the presence of molecular dioxygen to aldehydes and hydrogen peroxide. The catalytic centres contain a Cu atom and a topaquinone cofactor formed autocatalytically from a tyrosine residue in the presence of Cu and molecular oxygen. The structure of the Cu-containing amine oxidase from Arthrobacter globiformis, which was previously refined at 1.8 A resolution in space group C2 with unit-cell parameters a = 157.84, b = 63.24, c = 91.98 A, beta = 112.0 degrees [Wilce et al. (1997), Biochemistry, 36, 16116-16133], has been re-refined with newly recorded data at 1.55 A resolution. The structure has also been solved and refined at 2.2 A resolution in a new crystal form, space group C2, with unit-cell parameters a = 158.04, b = 64.06, c = 69.69 A, beta = 111.7 degrees.