Download MendeleySubstrate Orientation and Catalysis at the Molybdenum Site in Xanthine Oxidase: CRYSTAL STRUCTURES IN COMPLEX WITH XANTHINE AND LUMAZINE.
Pauff, J.M., Cao, H., Hille, R.(2009) J Biol Chem 284: 8760-8767
- PubMed: 19109252
- DOI: https://doi.org/10.1074/jbc.M804517200
- Primary Citation of Related Structures:
3ETR, 3EUB - PubMed Abstract:
Xanthine oxidoreductase is a ubiquitous cytoplasmic protein that catalyzes the final two steps in purine catabolism. We have previously investigated the catalytic mechanism of the enzyme by rapid reaction kinetics and x-ray crystallography using the poor substrate 2-hydroxy-6-methylpurine, focusing our attention on the orientation of substrate in the active site and the role of Arg-880 in catalysis. Here we report additional crystal structures of as-isolated, functional xanthine oxidase in the course of reaction with the pterin substrate lumazine at 2.2 A resolution and of the nonfunctional desulfo form of the enzyme in complex with xanthine at 2.6 A resolution. In both cases the orientation of substrate is such that the pyrimidine subnucleus is oriented opposite to that seen with the slow substrate 2-hydroxy-6-methylpurine. The mechanistic implications as to how the ensemble of active site functional groups in the active site work to accelerate reaction rate are discussed.
Organizational Affiliation:
Department of Biochemistry, University of California, Riverside, California 92521 and the Medical Scientist Program, The Ohio State University, Columbus, Ohio 43210, USA.
