Fasciola gigantica thioredoxin glutathione reductase: Biochemical properties and structural modeling.
Platyhelminth thioredoxin glutathione reductase (TGR) is a multifunctional enzyme that crosstalk between the conventional thioredoxin (Trx) and glutathione (GSH) system. It has been validated as a potential drug target in blood flukes. In the present study, we have performed a biochemical study on Fasciola gigantica TGR with substrates DTNB and GSSG. The Michaelis constant (Km) with DTNB was found to be 4.34±0.12μM while it was 61.15±1.50μM with GSSG. The kinetic results were compared with the TGR activities of other helminths. FgTGR showed typical hysteretic behavior with GSSG as other TGRs. We also described a homology-based structure of FgTGR. The cofactors (NADPH and FAD) and substrates (GSSG and DTNB) were docked, and two possible binding sites for substrates were identified in a single chain. The substrates were found to bind more favorably in the second site of TrxR domains. We also presented the first report on binding interaction of DTNB with a TGR. DTNB forms H-bond with His204 and Arg450 of chain A, Sec597, and Gly598 from chain B, salt-bridge with Lys124, and numerous other hydrophobic interactions. Helminth TGR represents an important enzyme in the redox and antioxidant system; hence, its inhibition can be used as an effective strategy against liver flukes.
Molecular and Structural Biophysics Laboratory, Department of Biochemistry, North-Eastern Hill University, Shillong 793022, India.
Ankita
A
Gupta
Centre for Advanced Studies in Crystallography and Biophysics, University of Madras, Guindy, Chennai 600025, India.
Manish
M
Kesherwani
Centre for Advanced Studies in Crystallography and Biophysics, University of Madras, Guindy, Chennai 600025, India.
Devadasan
D
Velmurugan
Molecular and Structural Biophysics Laboratory, Department of Biochemistry, North-Eastern Hill University, Shillong 793022, India. Electronic address: timir.tripathi@gmail.com.
Timir
T
Tripathi
D000595:Amino Acid Sequence; D000818:Animals; D055162:Biocatalysis; D002850:Chromatography, Gel; D003067:Coenzymes / Q000378:metabolism; D003198:Computer Simulation; D004220:Disulfides / Q000378:metabolism; D005209:Fasciola / Q000201:enzymology*; D019803:Glutathione Disulfide / Q000737:chemistry; D007328:Insulin / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification; D016415:Sequence Alignment; D013379:Substrate Specificity; D013879:Thioredoxins / Q000378:metabolism
D003067:Coenzymes; D004220:Disulfides; D007328:Insulin; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D013879:Thioredoxins; D009247:NADH, NADPH Oxidoreductases; C466433:thioredoxin glutathione reductase; D019803:Glutathione Disulfide
Homology modeling; Hysteresis; Liver fluke; Redox homeostasis; Thioredoxin glutathione reductase