Structure-function relationships in naturally occurring mutants of pancreatic lipase.

From primary structure comparison, the pancreatic lipase family is now divided into three subgroups: classical pancreatic lipases, pancreatic lipase-related proteins 1 (RPI) and pancreatic lipase-related proteins 2 (RP2). Among the RP2 subfamily, the guinea-pig and coypu enzymes share kinetic properties which differ from those of classical pancreatic lipases. Both enzymes display a high phospholipase activity and are not interfacially activated using a short chain triglyceride as substrate. Their activity towards insoluble triglycerides is inhibited by micellar concentrations of bile salts and is not restored by addition of colipase. These atypical kinetic properties are discussed in the light of amino acid sequence comparison between RP2 and classical pancreatic lipases, based on the closed and open conformations of the 3-D structure of human pancreatic lipase.