CRYSTAL STRUCTURE OF COPPER AMINE OXIDASE OF YEAST. Rongbao Li¹, Longying Chen¹, Goeffery Boyd¹, Daiying Cai², Judith Klinman² and F. Scott Mathews¹. ¹Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110; ²Department of Chemistry, University of California, Berkeley, CA 94720.

The copper-containing amine oxidase from the yeast Hansenula polymorpha has been solved by molecular replacement. It is a ubiquitous dimeric enzyme that catalyze the oxidative deamination of primary amines by molecular oxygen to the corresponding aldehydes, ammonium and hydrogen peroxide. Copper amine oxidases are a novel group of quinoenzymes that contain a covalently bound redox cofactor, 2,4,6-trihydroxyphenyl-alanine quinone (topa quinone, or TPQ) generated by post-translational modification of a single tyrosine side-chain. The enzymes allow the microorganism to use the appropriate amines as a carbon and nitrogen source for growth. In animals the enzymes modulate the levels of amines, thereby being implicated in cell growth, development and detoxication. Purified enzyme, expressed in Saccharomyces cerevisiae (Danying Cai and Judith P. Klinman, Biochemistry, 1994, 33, 7647-7653) was crystallized using vapor diffusion. The crystals are orthorhombic, with space group symmetry P2₁2₁2₁ and unit cell dimensions of a = 137.9 Å, b = 145.8 Å, c = 234.1 Å. Using a cryogenic cooling system the native protein crystals diffract x-rays to 2.3 Å resolution; however, due to the long unit cell axis the data were only collect to 2.9 Å with 97% completeness. There are two dimers in the asymmetric unit. The self-rotation function indicated that each dimer has two-fold symmetry and the two dimers are related by a two-fold axis. The molecular replacement solution is in good agreement with the self-rotation function results. The enzyme is about 28% homologous to copper amine oxidase of E. coli ; molecular replacement using the structure of this protein as a search probe (M. R. Parsons, M. A. Convery, C. M. Wilmont, K. D. S. Yadav, V. Blakeley, A. S. Corner, S. E. V. Philips, M. J. McPherson and P. F. Knowles, Structure 1995, 3, 1171-1179) has yielded a starting model which contains 90% of the residues. Refinement of this model is proceeding in combination with SIR determined phases.