Abstract: A purified enzyme-I is obtained that participates in C-terminal amidation by acting on a peptide C-terminal glycine adduct to form a peptide C-terminal .alpha.-hydroxyglycine adduct. The enzyme has an optimum pH of about 5 to 7, an optimum temperature of 25 to 40.degree. C. and a molecular weight of about 25 kDa or about 36 kDa, and metal ions and ascorbic acid act as a cofactor. A purified enzyme-II is obtained that participates in C-terminal amidation by acting on the peptide C-terminal .alpha.-hydroxyglycine adduct to produce a C-terminal amidated compound. The enzyme has an optimum pH of about 5 to 6, an optimum temperature of 15 to 35.degree. C. and a molecular weight of about 40 kDa or about 43 kDa. Enzyme-I does not act on the peptide C-terminal .alpha.-hydroxyglycine adduct and enzyme-II does not act on the peptide C-terminal glycine adduct. The enzymes may be purified from a biological material such as horse serum by affinity chromatography using a peptide C-terminal glycine adduct as a ligand.

Abstract: A purified enzyme-I is obtained that participates in C-terminal amidation by acting on a peptide C-terminal glycine adduct to form a peptide C-terminal .alpha.-hydroxyglycine adduct. The enzyme has an optimum pH of about 5 to 7, an optimum temperature of 25.degree. to 40.degree. C. and a molecular weight of about 25 kDa or about 36 kDa, and metal ions and ascorbic acid act as a cofactor. A purified enzyme-II is obtained that participates in C-terminal amidation by acting on a peptide C-terminal .alpha.-hydroxyglycine adduct to produce a C-terminal amidated compound. The enzyme has an optimum pH of about 5 to 6, an optimum temperature of 15.degree. to 35.degree. C. and a molecular weight of about 40 kDa or about 43 kDa. Enzyme-I does not act on the peptide C-terminal .alpha.-hydroxyglycine adduct and enzyme-II does not act on the peptide C-terminal glycine adduct.

Abstract: 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.