-!- The mammlian enzyme is part of the cell antioxidant defense mechanism. -!- It initiates extracellular glutathione (GSH) breakdown, provides cells with a local cysteine supply and contributes to maintain intracelular GSH levels. -!- The protein also has EC 3.4.19.13 activity. -!- The enzyme consists of two chains that are created by the proteolytic cleavage of a single precursor polypeptide. -!- The N-terminal L-threonine of the C-terminal subunit functions as the active site for both the cleavage and the hydrolysis reactions.

-!- The mouse enzyme is specific for leukotriene C(4), while the human enzyme also has considerable activity toward glutathione and oxidized glutathione (cf. EC 3.4.19.13).

-!- This is a bifunctional protein that also has the activity of EC 2.3.2.2. -!- The enzyme binds its substrate by forming an initial gamma-glutamyl- enzyme intermediate, releasing the L-cysteinylglycine part of the molecule. -!- The enzyme then reacts with either a water molecule or a different acceptor substrate (usually an L-amino acid or a dipeptide) to form L-glutamate or a product containing a new gamma-glutamyl isopeptide bond, respectively. -!- The enzyme acts on glutathione, glutathione-S-conjugates, and, at a lower level, on other substrates with an N-terminal L-gamma-glutamyl residue. -!- It plays a crucial part in the glutathione-mediated xenobiotic detoxification pathway. -!- The enzyme consists of two chains that are created by the proteolytic cleavage of a single precursor polypeptide.