Subunit Interactions of Human Glutathione Synthetase

• Published in: The FASEB journal Vol. 21; no. 6; p. A1011
• Main Authors: Carter, Monique J, Barakat, Khaldoon A, Cundari, Thomas R., Anderson, Mary E.
• Format: Journal Article
• Language: English
• Published: The Federation of American Societies for Experimental Biology 2007
• DOI: 10.1096/fasebj.21.6.A1011-b
• EISSN: 1530-6860
• ISSN: 0892-6638

Glutathione (GSH; γ‐glutamylcysteinylglycine), an abundant intracellular thiol, is imperative for reducing oxidative stress within biological systems. The synthesis of this antioxidant is achieved through two enzyme catalyzed reactions. Both reactions are ATP‐dependent and thought to proceed through an acyl phosphate intermediate. The first reaction, ligation of glutamate and cysteine, is catalyzed by γ‐glutamylcysteine synthetase (γ‐GCS) to yield γ‐glutamylcysteine. Glutathione synthetase (GS) catalyzes the second reaction, which adds glycine to γ‐glutamylcysteine to produce GSH. Human GS (hGS) is a homodimer with a subunit molecular weight of 52 kDa. Little is known about the dimer interface of GS. However, a known patient mutation in hGS (A26D) results in 15% of WT GS activity, GSH deficiency, and 5‐oxoprolinuria. These findings suggest that the dimer interface is important for hGS function. We have prepared, purified, and assayed mutant GS enzymes at the dimer interface. For example, we have found that the E43A mutant GS has lower (20% of WT) activity. Our studies on the dimer interface provide a better understanding of hGS and subunit interactions.
(Supported in part by: U.S. Dept. Ed. (CASCaM UNT, T.R.C), Faculty Research Grant UNT (T.R.C.), Research Enhancement Program Grant TWU (MEA), TWU Chemistry Dept. Welch Foundation Grant)