Binding of glutathione by rat liver cytosol

Glutathione (GSH) binding to rat liver cytosol at two different protein concentrations and a range of GSH concentrations was determined using rapid ultrafiltration. Two binding sites and nonspecific binding were determined by computer fit of the data. The high-affinity site had a similar affinity and capacity for GSH as that of the GSH S-transferases. Using the converged parameters and an estimation of cytosolic protein content of the intact liver, simulation of the GSH-free fraction and the contribution and degree of saturation of the high-affinity binding site were estimated over a broad range of GSH concentrations. The findings predict that 70-75% of cytosol GSH is free and that the high-affinity site is saturated with GSH in the physiologic range.