| Abstract
| - Human pancreatic lipase-related protein 2 (HPLRP2) was found to be expressed in the pancreas,but its biochemical properties were not investigated in detail. A recombinant HPLRP2 was produced ininsect cells and the yeast Pichia pastoris and purified by cation exchange chromatography. Its substratespecificity was investigated using pH-stat and monomolecular film techniques and various lipid substrates(triglycerides, diglycerides, phospholipids, and galactolipids). Lipase activity of HPLRP2 on trioctanoinwas inhibited by bile salts and poorly restored by adding colipase. In vivo, HPLRP2 therefore seemsunlikely to show any lipase activity on dietary fat. In human pancreatic lipase (HPL), residues R256,D257, Y267, and K268 are involved in the stabilization of the open conformation of the lid domain,which interacts with colipase. These residues are not conserved in HPLRP2. When the correspondingmutations (R256G, D257G, Y267F, and K268E) are introduced into HPL, the effects of colipase aredrastically reduced in the presence of bile salts. This may explain why colipase has such weak effects onHPLRP2. HPLRP2 displayed a very low level of activity on phospholipid micelles and monomolecularfilms. Its activity on monogalactosyldiglyceride monomolecular film, which was much higher, was similarto the activity of guinea pig pancreatic lipase related-protein 2, which shows the highest galactolipaseactivity ever measured. The physiological role of HPLRP2 suggested by the present results is the digestionof galactolipids, the most abundant lipids occurring in plant cells, and therefore, in the vegetables that arepart of the human diet.
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