Affinity of GSH to microsomal glutathione transferase 1 (MGST1) trimer

Value 320 µM Range: ±50 µM
Organism Rat Rattus norvegicus
Reference Alander et al., Microsomal glutathione transferase 1 exhibits one-third-of-the-sites-reactivity towards glutathione. Arch Biochem Biophys. 2009 Jul 1 487(1):42-8. p. 44 right column, 2nd paragraphPubMed ID19416719
Method To evaluate product binding, equilibrium dialysis studies were performed utilising GSDNB (1-S-glutathionyl-2,4-dinitrobenzene). When the data were fitted to a one site binding hyperbola (Eq. (1) and Fig. 3), Bmax was determined to 3.6±0.3 product molecules per trimer, and Kd to 320±50µM. This clearly shows three active-binding sites per trimer. Attempts to fit data to a two or a three site-binding equation did not improve the fit.
Comments Researchers' results show that three GSH molecules bind to each MGST1 trimer albeit with widely varying affinities (20µM–2.5mM). The GSH molecule in the catalytically competent thiolate anion form shows the highest affinity. A complex product inhibition pattern supports subunit cooperativity that is required for one-third-of-the-sites-reactivity. See BNID 105544, 105545, 105546
Entered by Uri M
ID 105547