The physiological role of pancreatic lipases has traditionally been assigned solely to triacylglyceride metabolism, while the digestion of phospholipids requires the presence of the pancreatic phospholipase A,, a 14-kDa enzyme unrelated to pancreatic lipases. However, in the guinea pig, it was observed that the pancreatic phospholipase A, was absent and that a guinea pig pancreatic-lipase-related protein 2 (GPL-RP2) was responsible for phospholipase activity, in contrast to the situation observed in other mammalian species. As the guinea pig is a member of the hystricomorph rodents, it was of interest to investigate if other species within this evolutionary suborder display similar characteristics. The coypu (Myoc,astor coypus) also a member of the hystricomorph rodents, was chosen for further investigations. The cDNAs encoding two pancreatic lipases and a procolipase from the coypu were cloned, expressed and characterized. One lipase, CoPL-RP2, was identified as belonging to the RP2 subfamily, while the second, CoPL, was found to belong to the classical pancreatic lipase subfamily. Enzymic characterization and sequence data suggest a role for coypu colipase as a specific cofactor for CoPL, while this coypu colipase cannot be an important cofactor for CoPL-RP2 in vivo. Also, the new lipase cDNA sequences were used in a phylogentic analysis to reinvestigate the taxonomical position of the hystricomorph rodents (e.g. cloypu and guinea pig) with respect to the myomorph rodents (e.g. rat and mouse) Keywov-ds. Baculovirus ; guinea pig ; hystricomorph rodents ; mass spectrum ; phylogeny.Pancreatic lipase (triacylglycerol hydrolase) fulfills a key function in dietary fat absorption by hydrolyzing triacylglycerides into diacylglycerides, monoacylglycerides and fatty acids in the digestive tract. Until recently, this lipase was considered as a single protein produced by the exocrine pancreas, even though two major isoforms (A and B) had previously been isolated from porcine [ l ] and human pancreas [2]. In fact, the main advances in the biochemical eharacterization of this enzyme were obtained with porcine pancreatic lipase B [3] until the three-dimensionalstructure of human pancreatic lipase (HPL) was resolved [4]. In addition to these classical pancreatic lipases, pancreatic lipaserelated proteins (PL,-RPs) have now been isolated from several species [5-lo]. Thie cloning and sequencing of two new PLRPs from human pancreas [6] has suggested the classification of pancreatic lipases as three subfamilies ; classical pancreatic lipases, PL-RP1 and PL-RP2. These pancreatic lipase subtypes Correspondence to K. Thirstrup, Laboratory for Molecular Endocrinology, Rigshospitalet 6321, Blegdamsvej 9, DK-2100 Copenhagen, Denmark Abbreviations. CoPL, coypu pancreatic lipase; CoPL-RP2, coypu pancreatic-lipase-related protein 2 ; ESMS, electrospray mass spectrum; GPL, guinea pig pancreatic lipase; GPL-FW2, guinea pig pancreaticlipase-related protein 2; HPL, human pancreatic lipase; HPL-RP1, human pancreatic-lipase-related protein 1 ; ...

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