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

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.

Comparison of Whole Body SOD1 Knockout with Muscle-Specific SOD1 Knockout Mice Reveals a Role for Nerve Redox Signaling in Regulation of Degenerative Pathways in Skeletal Muscle

“…6A, B) supported the reduction in structural proteins MBP and CX32 (MYP0) in Sod1 -/mice shown in Figure 2C-E. Significant changes were also detected in redox-regulated proteins, including PRDX 5 and thioredoxin reductase 1 (TRXR1), but also metabolic enzymes known to be redox regulated (14,33,35,62) including transketolase (TKT), isocitrate dehydrogenase (IDH3A), electron transport flavoprotein subunit alpha (ETFA), and the cytoskeletal regulator gelsolin (GELS) (Fig. 6A) were downregulated in SN of the Sod1 -/model.…”

“…Proteomic analyses conducted in this study revealed an altered proteome in peripheral nerve of Sod1 -/mice, associated with downregulation of a number of metabolic enzymes that appear to be redox mediated (14,33,35,62). Overall, the data presented in this study indicate that despite the observed PNS degeneration in Sod1 -/mice, peripheral nerve of this model does not exhibit altered redox homeostasis similar to that seen in the skeletal muscle that it innervates but an altered proteome and specific changes in key regulatory redox Cys residues.…”

Redox regulation of metabolic and signaling pathways by thioredoxin and glutaredoxin in NOS-3 overexpressing hepatoblastoma cells

“…It's up-regulation in NOS3 overexpressing cells ( Fig. 1 D) could be counterbalanced by inactivation through thiol oxidation [48] as shown in Fig. 4 B.…”

Oxoisoaporphines and Aporphines: Versatile Molecules with Anticancer Effects

“…The first studies of the Agarwal et al and Huang et al highlighted that the inhibition of heme biosynthesis could be the principal mechanism of action of sampangine [133,146]. Heme is present in complexes III and IV of the electron transport chain and possibly affects the heme dysfunction in sampangine-induced ROS production, as iron and various heme biosynthetic intermediates are known to be oxidized via reaction with cellular ROS [147][148][149][150].…”