The amino terminal sequences of acid proteases-human pepsin and gastricsin and the protease of Rhizopus chinensis.

The amino acid sequences near the amino termini of human pepsin (34 residues) and gastricsin (24 residues) and the acid protease from $\text{Rhizopus chinensis}$ (27 residues) have been determined using automated Edman degradation. From these results three additional observations were made. First, two structural variants have been observed for human gastricsin and for the $\text{Rhizopus}$ protease. Both cases are apparently genetic in origin. Second, a stretch of sequence in the $\text{Rhizopus}$ protease, residues 14 to 26, is highly homologous to the known sequence of porcine pepsin at the region of residues 11 to 23. Third, the sequences of the NH₂-terminal region of human pepsin and gastrisin are homologous.