Variability of Glutathione S-Transferase α in Human Liver and Plasma

Background: Glutathione S-transferases are a family of enzymes involved in the binding, transport, and detoxification of a wide variety of endogenous and exogenous compounds. Little information is available about the variability of class α glutathione S-transferases in human liver, where they are highly expressed, or in serum. Methods: Both total class α glutathione S-transferase (GST-α, composed of GSTA1-1, GSTA1-2, and GSTA2-2) as well as GSTA1-1 concentrations were measured by specific and sensitive ELISA in liver cytosols of 35 organ donors and in plasma samples of 350 healthy controls. Results: The mean total GST-α and GSTA1-1 in liver cytosols were 25.1 ± 9.4 and 10.7 ± 5.3 μg/mg protein, respectively, and did not correlate with activities of aspartate aminotransferase or alanine aminotransferase. The mean total GST-α in liver was significantly higher in females compared with males (28.8 ± 10.0 vs 22.0 ± 7.8 μg/mg protein; P <0.05). In contrast, the median total GST-α in plasma was lower in females compared with males (2.0 and 2.8 μg/L, respectively; P <0.0001). The median ratios for GSTA1-1/total GST-α in liver and plasma were 0.42 and 0.58, respectively. Conclusions: GSTA1-1 constitutes approximately one-half of the total amount of α class GSTs in human plasma and liver. Total GST-α values are higher in female liver but lower in plasma compared with the respective values in males.