Brain Specific Serine Protease 4 (BSSP4)

The deduced 317-amino acid protein contains an N-terminal hydrophobic leader peptide, followed by a propeptide sequence and the serine protease domain, which has the catalytic triad of histidine, aspartic acid, and serine. PRSS22 also has 2 cysteines that form a disulfide bond linking the propeptide and the catalytic domain following proteolytic activation, and it has an N-glycosylation site. PRSS22 lacks a number of residues required by other tryptases to form tetramers. RNA dot blot analysis detected abundant PRSS22 expression in adult esophagus and trachea, with lower levels in adult placenta, pancreas, prostate, and thyroid, and in fetal kidney and lung. There was little to no expression in other tissues examined. Enzymatically active PRSS22 was secreted from a human epithelial cell line and from transfected COS-7 cells.