Pro HD5 is stored and secreted from granules of Paneth cells in the small intestine (Porter et al. 1997, Cunliffe et al. 2001). The serine protease tryspin colocalizes to these granules as the inactive zymogen trypsinogen. Removal of the defensin propiece occurs extracellularly after release in to the crypt lumen, and is mediated by trypsin 2 (anionic trypsin) and/or trypsin-3 (mesotrypsin) which are converted to their active forms by enteroprotease like enzymes or by autoactivation (Ghosh et al. 2002, Ouelette 2011).