A novel human cDNA, termed PRSS11-L, was isolated which encodes a polypeptide that belongs to the S2/HtrA serine protease family. The PRSS11-L mRNA is widely expressed in several tissues throughout the body by multi-tissue Northern blotting. The full-length PRSS11-L cDNA, was cloned, expressed and purified. Proteolytic activity was demonstrated using the protein substrate casein. The isolated nucleic acid or polypeptide molecule of the invention can be used in detection assays, gene therapy, and screening assays.