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Publication Abstract from PubMed

Trypanosomes are purine-auxotrophic parasites that depend upon nucleoside hydrolase (NH) activity to salvage nitrogenous bases necessary for nucleic acid and cofactor synthesis. Nonspecific and purine-specific NHs have been widely studied, yet little is known about the 6-oxopurine-specific isozymes, although they are thought to play a primary role in the catabolism of exogenously derived nucleosides. Here, we report the first functional and structural characterization of the inosine-guanosine-specific NH from Trypanosoma brucei brucei. The enzyme shows near diffusion-limited efficiency coupled with a clear specificity for 6-oxopurine nucleosides achieved through a catalytic selection of these substrates. Pre-steady-state kinetic analysis reveals ordered product release, and a rate-limiting structural rearrangement that is associated with the release of the product, ribose. The crystal structure of this trypanosomal NH determined to 2.5 A resolution reveals distinctive features compared to those of both purine- and pyrimidine-specific isozymes in the framework of the conserved and versatile NH fold. Nanomolar iminoribitol-based inhibitors identified in this study represent important lead compounds for the development of novel therapeutic strategies against trypanosomal diseases.

Structure and mechanism of the 6-oxopurine nucleosidase from Trypanosoma brucei brucei.,Vandemeulebroucke A, Minici C, Bruno I, Muzzolini L, Tornaghi P, Parkin DW, Versees W, Steyaert J, Degano M Biochemistry. 2010 Oct 19;49(41):8999-9010. PMID:20825170^[1]

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