Hydrolyzes the polyglutamate sidechains of pteroylpolyglutamates. Progressively removes gamma-glutamyl residues from pteroylpoly-gamma-glutamate to yield pteroyl-alpha-glutamate (folic acid) and free glutamate (PubMed:11005824, PubMed:8816764). May play an important role in the bioavailability of dietary pteroylpolyglutamates and in the metabolism of pteroylpolyglutamates and antifolates. {ECO:0000269|PubMed:11005824, ECO:0000269|PubMed:8816764}. This is the function of Ensembl gene identifier ENSG00000137563 (GGH, gamma-glutamyl hydrolase).