May catalyze the degradation of intercellular cohesive structures in the cornified layer of the skin in the continuous shedding of cells from the skin surface. Specific for amino acid residues with aromatic side chains in the P1 position. Cleaves insulin A chain at '14-Tyr-|-Gln-15' and insulin B chain at '6-Leu-|-Cys-7', '16-Tyr-|-Leu-17', '25-Phe-|-Tyr-26' and '26-Tyr-|-Thr-27'. Could play a role in the activation of precursors to inflammatory cytokines. Cleavage of proteins with aromatic side chains in the P1 position. Inhibited by Zn2+ and Cu2+ at low micromolar concentrations. Inhibited by SERPINA12 (By similarity). Expressed in skin and, at lower levels, in lung, kidney, brain, heart and spleen. In skin, expressed in high suprabasal keratinocytes and in the luminal parts of hair follicles. Not detected in liver and skeletal muscle. Belongs to the peptidase S1 family. Kallikrein subfamily.