Primary substrate specificity of recombinant human stratum corneum chymotryptic enzyme.

Stratum corneum chymotryptic enzyme (SCCE) is a new human serine proteinase expressed by keratinocytes in the epidermis. Its function may be to catalyze the degradation of intercellular cohesive structures in the cornified layer of the skin in the continuous sheeding of cells from the skin surface. In this work the primary substrate specificity of recombinant SCCE was determined with oxidized bovine insulin B chain as substrate. Cleavage products were separated with high performance liquid chromatography and analyzed by amino acid sequence analysis and mass spectrometry. Cleavage sites were localized to Leu 6-cysteic acid 7, Tyr 16-Leu 17, Phe 25-Tyr 26, and Tyr 26-Thr 27 in insulin B chain. It is concluded that SCCE belongs to the family of serine endoproteinases specific for amino acid residues with aromatic side chains in the P1 position.