Has no serine protease inhibitory activity, probably due to mutations in the scaffold impairing conformational change. Detected in a restricted number of tissues, including lung, placenta, prostate, and tonsil. According to some authors, 4 of the identified SERPIN11 transcripts contained coding sequences that could be distinguished by different combinations of single nucleotide polymorphisms (designated SERPINB11a, SERPINB11b, SERPINB11c, and SERPINB11d), and one contained a nonsense mutation introducing a premature stop codon in position 90 identified in the official genome sequence (SERPINB11f) (PubMed:17562709). The sequence displayed here corresponds to SERPINB11a. Belongs to the serpin family. Ov-serpin subfamily. Mutations in the scaffold leading to either a stop codon instead of a Glu at position 90, an Arg instead of the well conserved Trp at position 188, or a Pro instead of Ser at position 303 lead to the loss of inhibitory activity.