Transmembrane Protease Serine 11B (TMPRSS11B) is a single-pass type II membrane protein member of the peptidase S1 family. TMPRSS11B contains one peptidase S1 domain and one SEA domain. TMPRSS11B is a serine protease that may play some biological role in the host defense system on the mucous membrane independently of or in cooperation with other substances in airway mucous or bronchial secretions.