Purification and cloning of a γ-glutamyl transpeptidase from onion (Allium cepa)

Onion γ-glutamyl transpeptidase catalyses hydrolysis of γ-glutamyl linkages in γ-glutamyl peptides and transfer of the γ-glutamyl group to amino acids and peptides and has high affinity for glutathione and glutathione conjugates.