Product activation of pancreatic lipase. Lipolytic enzymes as probes for lipid/water interfaces.
During the action of pancreatic lipase and colipase on racemic 1,2-didodecanoylglycerol monolayers in the absence of bile salts, biphasic kinetics was observed under conditions of high lipid packing. Similar kinetics has earlier been reported using phospholipid-emulsified triolein droplets (Borgström, B. (1980) Gastroenterology 78, 954-962). These kinetics are characterized by a lag time tau d, dependent on products accumulation at the substrate/water interface. This lag time is differentiated from the previously described enzyme concentration independent lag time tau i in systems of low lipid packing (Verger, R., Mieras, M. C. E., and de Haas, G. H. (1973) J. Biol. Chem. 248, 4023-4034). Both tau i and tau d reflect a rate-limiting step due to the slow enzyme penetration into the substrate interface. The variation of tau d under different conditions (change in pH and concentration of Ca2+, enzyme, bovine serum albumin, and lipolytic products) lead us to propose a model for the product activation during lipolysis. We will discuss the use of the pancreatic lipase-colipase system to probe the lipid packing of emulsified triglyceride particles and lipoproteins using tau d as a reference value.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D003089:Colipases / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008049:Lipase / Q000378:metabolism*; D008066:Lipolysis; D010179:Pancreas / Q000201:enzymology*; D011312:Pressure; D013499:Surface Properties; D013552:Swine
D003089:Colipases; D008049:Lipase; D002118:Calcium