Amino acid sequence of penicillopepsin. IV. Myxobacter AL-1 protease II and Staphylococcus aureus protease fragments and homology with pig pepsin and chymosin

Abstract

The digest of penicillopepsin (EC 3.4.23.7) with protease II from Myxobacter AL-1 gave 5 fragments which were separated on a Biogel P-100 column in 70% formic acid. The fragments were from 16-125 amino acids long. Two fragments were also isolated from a digest with a protease from S. aureus. The analysis of these fragments by automatic sequencer gave a number of overlaps of the chymotryptic and thermolytic peptides. The available amino acid sequence data for penicillopepsin described in this paper and the accompanying papers were combined and yielded 15 fragments which range in lengths from 3-112 amino acid residues. These unique fragments account for virtually all the amino acids of the fungal protease. Four of the fragments with a total of 194 residues (about 60% of the molecule) have been aligned with corresponding sections of pig pepsin (EC 3.4.23.1) and with part of the N-terminal sequence available for calf chymosin (EC 3.4.23.4). In the alignments about 37% of the residues in the fungal enzyme are identical with at least 1 of the mammalian enzymes. An additional 20% are chemically similar. These results, together with previously reported activesite directed modifications, show conclusively that penicillopepsin is an evolutionary homologue of the mammalian acid proteases.