ATP + L-cysteine + L-glutamate = ADP + gamma-L-glutamyl-L-cysteine + H(+) + phosphate Feedback inhibition by glutathione. Sulfur metabolism; glutathione biosynthesis; glutathione from L-cysteine and L-glutamate: step 1/2. Heterodimer of a catalytic heavy chain and a regulatory light chain. Most abundant in kidney. Also found in liver and testis. Belongs to the glutamate--cysteine ligase type 3 family.