A C-terminal amidating enzyme composition is disclosed having the ability to amidate the C-terminus of peptides with a C-terminal glycine. The C-terminal amidating enzyme is characterized by having a stable pH range of 5 to 9, metal ions and L-ascorbic acid as cofactors, two active fractions at molecular weights of about 50,000 and about 100,000 as determined from gel filtration, isoelectric points of about 4.5 pH for the active fraction having a molecular weight of about 50,000 and about 6.7 pH for the active fraction having a molecular weight of about 100,000 according to isoelectric point chromatography, and is activated by addition of catalase.