Title

Exploring the Potent Inhibition of CTP Synthase by Gemcitabine-5′-Triphosphate

Document Type

Article

Publication Date

12-2-2016

Abstract

© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim CTP synthase (CTPS) catalyzes the conversion of UTP to CTP and is a target for the development of antiviral, anticancer, antiprotozoal, and immunosuppressive agents. Exposure of cell lines to the antineoplastic cytidine analogue gemcitabine causes depletion of intracellular CTP levels, but the direct inhibition of CTPS by its metabolite gemcitabine-5′-triphosphate (dF-dCTP) has not been demonstrated. We show that dF-dCTP is a potent competitive inhibitor of Escherichia coli CTPS with respect to UTP [Ki=(3.0±0.1) μm], and that its binding affinity exceeds that of CTP ≈75-fold. Site-directed mutagenesis studies indicated that Glu149 is an important binding determinant for both CTP and dF-dCTP. Comparison of the binding affinities of the 5′-triphosphates of 2′-fluoro-2′-deoxycytidine and 2′-fluoro-2′-deoxyarabinocytidine revealed that the 2′-F-arabino group contributes markedly to the strong binding of dF-dCTP. Geminal 2′-F substitution on UTP (dF-dUTP) did not result in an increase in binding affinity with CTPS. Remarkably, CTPS catalyzed the conversion of dF-dUTP into dF-dCTP, thus suggesting that dF-dCTP might be regenerated in vivo from its catabolite dF-dUTP.

This document is currently not available here.

Share

COinS