GSR and cystic kidney disease: Levels of GSH biosynthetic enzymes were also downregulated in renal cysts, including the catalytic subunit of the rate-limiting enzyme glutamyl cysteine ligase (GCLC, −2.5×), glutathione synthetase (GSS, −1.9×), and glutathione reductase (GSR, −2.3×) (Figure 3).