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Oxidative Medicine and Cellular Longevity
Volume 2013 (2013), Article ID 932472, 13 pages
http://dx.doi.org/10.1155/2013/932472
Research Article

Thiol Redox Sensitivity of Two Key Enzymes of Heme Biosynthesis and Pentose Phosphate Pathways: Uroporphyrinogen Decarboxylase and Transketolase

1Department of Biochemistry and Molecular Biology, University of Córdoba and Córdoba Maimónides Institute for Biomedical Research (IMIBIC), 14071 Córdoba, Spain
2Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease (IACD), University of Liverpool, Liverpool L69 3GA, UK
3Molecular Signaling and Antioxidant Systems in Plants, Department of Experimental Biology, University of Jaén, 23071 Jaén, Spain

Received 24 April 2013; Revised 10 June 2013; Accepted 19 June 2013

Academic Editor: Paula Ludovico

Copyright © 2013 Brian McDonagh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Uroporphyrinogen decarboxylase (Hem12p) and transketolase (Tkl1p) are key mediators of two critical processes within the cell, heme biosynthesis, and the nonoxidative part of the pentose phosphate pathway (PPP). The redox properties of both Hem12p and Tkl1p from Saccharomyces cerevisiae were investigated using proteomic techniques (SRM and label-free quantification) and biochemical assays in cell extracts and in vitro with recombinant proteins. The in vivo analysis revealed an increase in oxidized Cys-peptides in the absence of Grx2p, and also after treatment with H2O2 in the case of Tkl1p, without corresponding changes in total protein, demonstrating a true redox response. Out of three detectable Cys residues in Hem12p, only the conserved residue Cys52 could be modified by glutathione and efficiently deglutathionylated by Grx2p, suggesting a possible redox control mechanism for heme biosynthesis. On the other hand, Tkl1p activity was sensitive to thiol redox modification and although Cys622 could be glutathionylated to a limited extent, it was not a natural substrate of Grx2p. The human orthologues of both enzymes have been involved in certain cancers and possess Cys residues equivalent to those identified as redox sensitive in yeast. The possible implication for redox regulation in the context of tumour progression is put forward.