3eub

Publication Abstract from PubMed

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.

Substrate Orientation and Catalysis at the Molybdenum Site in Xanthine Oxidase: CRYSTAL STRUCTURES IN COMPLEX WITH XANTHINE AND LUMAZINE.,Pauff JM, Cao H, Hille R J Biol Chem. 2009 Mar 27;284(13):8760-7. Epub 2008 Dec 24. PMID:19109252^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.