L. donovani XPRT: Molecular characterization and evaluation of inhibitors

Publication date: Available online 9 December 2017 Source:Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics Author(s): Bhumi Patel, Dhaval Patel, Krupali Parmar, Rupal Chauhan, Desh Deepak Singh, Anju Pappachan Among all PRT enzymes of purine salvage pathway in Leishmania, XPRT (Xanthine phosphoribosyl transferase) is unique in its substrate specificity and their non-existence in human. It is an interesting protein not only for drug designing but also to understand the molecular determinants of its substrate specificity. Analysis of the 3D model of L. donovani XPRT (Ld-XPRT) revealed that Ile 209, Glu 215 and Tyr 208 may be responsible for the altered substrate specificity of Ld-XPRT. Comparisons with it's nearest homologue in humans, revealed significant differences between the two. A 28 residue long unique motif was identified in Ld-XPRT, which showed highest fluctuation upon substrate binding during MD simulations. In kinetic analysis, Ld-XPRT could phosphoribosylate xanthine, hypoxanthine and guanine with Km values of 7.27, 8.13, 8.48μM and kcat values of 2.24, 1.82, 1.19min−1 respectively. Out of 159 compounds from docking studies, six compounds were characterized further by fluorescence spectroscopy, CD spectroscopy and enzyme inhibition studies. Fluorescence quenching experiment was performed to study the binding of inhibitors with Ld-XPRT and dissociation constants were calculated. Four compounds are bi-substrate analogues and show competitive i...
Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - Category: Biochemistry Source Type: research