C‐Terminal‐Sequence Determination by Carboxypeptidase C from Orange Leaves

Abstract

Carboxypeptidase C isolated from orange leaves has been investigated for its use in C‐terminal sequence determinations. The sequence of the first six C‐terminal residues of the denatured protein ribonuclease could be deduced unequivocally from a time‐release plot of an incubation mixture containing 1 mole % of the enzyme. No release of free amino acids by autodigestion of the enzyme could be detected after prolonged periods of incubation. Three different peptides have been degraded demonstrating sufficient and comparable rates of release of all protein amino acids, including proline. Thus the enzyme reveals a broad specificity for acidic, neutral and basic amino acids and combines the activity and specificity of the pancreatic carboxypeptidases A and B, but in addition releases the imino acid proline. Copyright © 1972, Wiley Blackwell. All rights reserved