Rabbit Anti-GCLC polyclonal antibody for IHC-P, WB. Gamma Glutamylcystuene Synthetase (GSH) is the first enzyme and rate limiting step in the slutathione biosynthesis pathway. Glutathione (GSH) plays an important role in detoxification of oxidants and toxins from the cells. In most cells, GSH is synthesized denovo in two steps catalysed by Gamma Glutamylcysteine Synthetase (GCS) / Glutamate-cystein Ligase and GSH homeostasis. It is composed of two subunits: heavy and light. These subunits are coded by different genes which are controlled by different mechanisms. The heavy subunit carries the catalytic activity and can be inhibited through feedback mechanism by GSH. Binding of light subunit to heavy subunit reduces the Michaelis-Menten constant for glutamate to a physiological concentration of 1.2mM and increases the inhibitory constant for GSH.