Human pancreatic lipase-related protein 2 is a galactolipase.
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 in insect cells and the yeast Pichia pastoris and purified by cation exchange chromatography. Its substrate specificity was investigated using pH-stat and monomolecular film techniques and various lipid substrates (triglycerides, diglycerides, phospholipids, and galactolipids). Lipase activity of HPLRP2 on trioctanoin was inhibited by bile salts and poorly restored by adding colipase. In vivo, HPLRP2 therefore seems unlikely 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 corresponding mutations (R256G, D257G, Y267F, and K268E) are introduced into HPL, the effects of colipase are drastically reduced in the presence of bile salts. This may explain why colipase has such weak effects on HPLRP2. HPLRP2 displayed a very low level of activity on phospholipid micelles and monomolecular films. Its activity on monogalactosyldiglyceride monomolecular film, which was much higher, was similar to the activity of guinea pig pancreatic lipase related-protein 2, which shows the highest galactolipase activity ever measured. The physiological role of HPLRP2 suggested by the present results is the digestion of galactolipids, the most abundant lipids occurring in plant cells, and therefore, in the vegetables that are part of the human diet.
Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, CNRS UPR 9025, IBSM, Marseille, France.
Barbara
B
Sias
Francine
F
Ferrato
Philippe
P
Grandval
Dominique
D
Lafont
Paul
P
Boullanger
Alain
A
De Caro
Bernard
B
Leboeuf
Robert
R
Verger
Frédéric
F
Carrière
D000818:Animals; D001647:Bile Acids and Salts / Q000737:chemistry; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D002460:Cell Line; D003089:Colipases / Q000737:chemistry; D004789:Enzyme Activation; D038983:Galactolipids / Q000378:metabolism; D006801:Humans; D008049:Lipase / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008066:Lipolysis; D010189:Pancreatic Juice / Q000201:enzymology*; D010743:Phospholipids / Q000378:metabolism; D010843:Pichia / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018411:Spodoptera / Q000235:genetics; D013379:Substrate Specificity
D001647:Bile Acids and Salts; D003089:Colipases; D038983:Galactolipids; D010743:Phospholipids; D011994:Recombinant Proteins; C009909:monogalactosyldiacylglycerol; D002265:Carboxylic Ester Hydrolases; C019262:galactolipase; D008049:Lipase; C075988:pancreatic lipase related protein 2