GGH is a homodimeric protein which catalyzes the cleavage of the gamma-glutamyl chain of folylpoly-gamma-glutamyl substrates. GGH is a vital enzyme in folyl and antifolyl poly-gamma-glutamate metabolism and it has a significant part in the bioavailability of dietary pteroylpolyglutamates and in the metabolism of antifolates and pteroylpolyglutamates.