Anti-serine peptidase inhibitor Kazal type 13 antibodies are used for the immunodetection of the protein encoded by the SPINK13 gene. In humans, the canonical protein has a reported length of 94 amino acid residues and a mass of 11.1 kDa. It is known to be a secreted protein. Alternative splicing is reported to yield 2 different isoforms for this protein. It is believed to be a serine protease inhibitor (By similarity). Post-translational modifications have been described, including glycosylation. Other names for this target antigen include Hepatitis B Virus (HBV) DNA polymerase transactivated protein 1, hepatitis B virus DNA polymerase transactivated human serine protease inhibitor, and serine protease inhibitor Kazal-type 13. Gene orthologs have been identified in the mouse, rat, bovine and chimpanzee species.