Abstract: A peptide amidase isolated from the flavedo of citrus fruits, preferably oranges, which is capable of catalyzing the selective hydrolytic elimination of the free amino group on the C-terminal end of peptide amides but which does not cleave peptide bonds. The enzyme accepts D-amino acid residues in the C-terminal position, although the hydrolysis rate is much slower than with L-amino acid residues. The enzyme is weakly inhibited by serine protease inhibitors; has an optimal pH of 7.5.+-.1.5, an optimum temperature of 30.degree. C. at pH 7.5 and has an isoelectric point of pH 9.5. The peptide amidase is stable at pH 6.0-9.0. The molecular weight of the purified enzyme is 32,000.+-.3000 daltons. A peptide amidase according to the present invention is particularly useful in the production of peptides by continuous enzymatic reaction of N-protected amino acid or peptide alkyl esters with amides of amino acids.

Abstract: A peptide amidase isolated from the flavedo of citrus fruits, preferably oranges, which is capable of catalyzing the selective hydrolytic elimination of the free amino group on the C-terminal end of peptide amides but which does not cleave peptide bonds. The enzyme accepts D-amino acid residues in the C-terminal position, although the hydrolysis rate is much slower than with L-amino acid residues. The enzyme is weakly inhibited by serine protease inhibitors; has an optimal pH of 7.5.+-.1.5, an optimum temperature of 30.degree. C. at pH 7.5 and has an isoelectric point of pH 9.5. The peptide amidase is stable at pH 6.0-9.0. The molecular weight of the purified enzyme is 23,000 +/- 3000 daltons. A peptide amidase according to the present invention is particular useful in the production of peptides by continuous enzymatic reaction of N-protected amino acid or peptide alkyl esters with amides of amino acids.