Abstract
UDP-galactopyranose mutase (UGM) is a flavoenzyme that catalyzes the conversion of UDP-galactopyranose to UDP-galactofuranose, the precursor of galactofuranose (Galf). Galf is found in several pathogenic organisms, including the parasite Trypanosoma cruzi, the causative agent of Chagas' disease. Galf) is important for virulence and is not present in humans, making its biosynthetic pathway an attractive target for the development of new drugs against T. cruzi. Although UGMs catalyze a non-redox reaction, the flavin must be in the reduced state for activity and the exact role of the flavin in this reaction is controversial. The kinetic and chemical mechanism of TcUGM was probed using steady state kinetics, trapping of reaction intermediates, rapid reaction kinetics, and fluorescence anisotropy. It was shown for the first time that NADPH is an effective redox partner of TcUGM. The substrate, UDP-galactopyranose, protects the enzyme from reacting with molecular oxygen allowing TcUGM to turnover ~1000 times for every NADPH oxidized. Spectral changes consistent with a flavin iminium ion, without the formation of a flavin semiquinone, were observed under rapid reaction conditions. These data support the proposal of the flavin acting as a nucleophile. In support of this role, a flavin-galactose adduct was isolated and characterized. A detailed kinetic and chemical mechanism for the unique non-redox reaction of UGM is presented. © 2012 Oppenheimer et al.
Recommended Citation
M. Oppenheimer et al., "Chemical Mechanism of UDP-galactopyranose Mutase from Trypanosoma Cruzi: A Potential Drug Target Against Chagas' Disease," PLoS ONE, vol. 7, no. 3, article no. e32918, Public Library of Science, Mar 2012.
The definitive version is available at https://doi.org/10.1371/journal.pone.0032918
Department(s)
Chemistry
Publication Status
Open Access
International Standard Serial Number (ISSN)
1932-6203
Document Type
Article - Journal
Document Version
Final Version
File Type
text
Language(s)
English
Rights
© 2024 The Authors, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution 4.0 License.
Publication Date
20 Mar 2012
PubMed ID
22448231
Comments
National Institute of General Medical Sciences, Grant R01GM094469