N-terminal amino acid sequences of acid proteases: acid proteases from Penicillium roqueforti and Rhizopus chinensis and alignment with penicillopepsin and mammalian proteases

Abstract

The amino-terminal sequence (33 residues) of the acid protease from P. roqueforti was determined with an automated sequencer. The amino-terminal sequence of Rhizopus pepsin was extended from 27 residues to 39 residues. It was found that 2 forms of Rhizopus pepsin differ in position 15, where Rhizopus pepsin I has an isoleucine and Rhizopus pepsin II a valine residue. The new sequences were aligned with the amino-terminal sequences of penicillopepsin (EC 3.4.23.7), pig pepsin (EC 3.4.23.1), calf chymosin (EC 3.4.23.4), human pepsin (EC 3.4.23.2), human gastricsin (EC 3.4.23.3), and cow pepsin (EC 3.4.23.1). Residues 31-35 (numbering based on pig pepsin) are identical in all enzymes. This section contains 1 of the 2 aspartic acids (Asp-32) implicated in the active site. The similarity of the sequences provides strong evidence for the homology of these acid proteases.