Serine Peptidase Inhibitor Kazal Type 9 (SPINK9)

SPINK9 encodes a Kazal-type serine protease inhibitor expressed in human skin. The protein has a signal cleavage site between amino acids 19 and 20. Immunohistochemical analysis and Western blot analysis revealed that SPINK9 protein expression appeared limited to palmoplantar stratum corneum.The deduced 86-amino acid protein contains 3 Kazal domains that include a conserved tyrosine residue and conserved number and spacing of cysteines and disulfide bonds. The expression of SPINK9 mRNA increased with differentiation in cultured primary keratinocytes. Immunohistochemical analysis detected SPINK9 in palmoplantar stratum granulosum and stratum corneum, with no immunoreactivity detected at other sites of normal human skin. SPINK9 was also highly expressed at sites of hyperkeratosis.