The acidic upper small intestine in CF may contribute to fat malabsorption given: 1) the inactivation of trypsin, which induces an impairment of active enzyme molecules from their zymogen form (pancreatic lipase, PLA2); 2) the inactivation of pancreatic lipase [131]; 3) BA precipitation, decreasing the BA pool and diminishing its availability to form micelles; and 4) early protonation, which impairs the micellar dispersion of lipolytic products [132]. The gene discussed is PNLIP; the disease is cystic fibrosis.