Shows particularly broad specificity; although bonds involving phenylalanine and leucine are preferred, many others are also cleaved to some extent. Preferential cleavage: hydrophobic, preferably aromatic, residues in P1 and P1' positions. Cleaves 1-Phe-|-Val-2, 4-Gln-|-His-5, 13-Glu-|-Ala-14, 14-Ala-|-Leu-15, 15-Leu-|-Tyr-16, 16-Tyr-|-Leu-17, 23-Gly-|-Phe-24, 24-Phe-|-Phe-25 and 25-Phe-|-Tyr-26 bonds in the B chain of insulin. Pepsin A-2 is predominant at the 4-month stage. Pepsin A-3 is predominant at fetal stages. Pepsin A-2 is phosphorylated, but not pepsin A-3. Each pepsinogen is converted to corresponding pepsin at pH 2.0 in part as a result of the release of a 47 AA activation segment and in part as a result of stepwise proteolytic cleavage via an intermediate form(s). The expression of pepsinogen genes is regulated by hormones and related substances. Belongs to the peptidase A1 family. It is not known if this is Pep A-2 or Pep A-3.