Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Colipases”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 217 records · Page 12Linked to original sources
PubMed2001

The lipase C-terminal domain. A novel unusual inhibitor of pancreatic lipase activity.

In vertebrates, dietary fat digestion mainly results from the combined effect of pancreatic lipase, colipase, and bile. It has been proposed that in vivo lipase adsorption on oil-water emulsion is mediated by a preformed lipase-colipase-mixed micelle complex. The main lipase-colipase binding site is located on the C-terminal domain of the enzyme. We report here that in vitro the isolated C-terminal domain behaves as a potent noncovalent inhibitor of lipase and that the inhibitory effect is triggered by the presence of micelles. Lipase inhibition results from the formation of a nonproductive C-terminal domain-colipase-micelle ternary complex, which competes for colipase with the active lipase-colipase-micelle ternary complex, thus diverting colipase from its lipase-anchoring function. The formation of such a complex has been evidenced by molecular sieving experiments. This nonproductive complex lowers the amount of active lipase thus reducing lipolysis. Preliminary experiments performed in rats show that the C-terminal domain also behaves as an inhibitor in vivo and thus could be considered a potential new tool for specifically reducing intestinal lipolysis.

Animals↗
PubMed1993

Does the bile salt-stimulated lipase of human milk have a role in the use of the milk long-chain polyunsaturated fatty acids?

Long-chain polyunsaturated (LCP) fatty acids derived from linoleic (18:2 n-6) and alpha-linolenic (18:3 n-3) acids are considered essential nutrients in preterm infants. The efficiency by which such fatty acids are released as absorbable products from triacylglycerol was explored in vitro using rat chylomicron triacylglycerol as substrate. When incubated with purified human pancreatic colipase-dependent lipase and colipase, arachidonic acid (20:4 n-6) was released less efficiently than linoleic acid from such triacylglycerol. This difference was not seen when purified human milk bile salt-stimulated lipase (BSSL) was incubated with the triacylglycerol substrate, and it was almost abolished when colipase-dependent lipase (with colipase) and BSSL acted simultaneously, as they do in breast-fed infants. There was no difference in arachidonic acid and eicosapentaenoic acid (20:5 n-3) release rates with either colipase-dependent lipase or BSSL, albeit the release was more rapid with the milk enzyme than with colipase-dependent lipase. Again, the most efficient release as absorbable free fatty acids was achieved when the two lipases operated together. The relative resistance to hydrolysis of arachidonic acid and eicosapentaenoic acid by colipase-dependent lipase was best explained by the localization of the first double bond to the delta-5 position of the respective fatty acid. The results obtained suggest that BSSL is of importance for the efficient use of human milk LCP fatty acids.

Animals↗
PubMed1994

Monoclonal antibodies to human pancreatic procolipase: production and characterization by competitive binding studies.

Hybridomas secreting monoclonal antibodies (MAbs) specific for human pancreatic colipase were established and 11 clones were selected by using a dot immunobinding assay. Characterization of the MAbs was carried out by using direct and competitive epitope mapping methods, including ELISA and inactivation of colipase-dependent pancreatic lipase. Monoclonal antibodies showed four distinct patterns of reactivity. Monoclonal antibody 5.30 (group I) inhibited colipase-dependent lipase activity. The dissociation constant of the inactive antibody-antigen complex was 10(-9) M. Monoclonal antibodies 48.30, 66.24, and 153.23 (group II) had no effect on activity although they bound competitively with MAb 5.30 to antigen as shown by their capacity to displace MAb 5.30 from the antibody-antigen complex and by ELISA additivity test. Dissociation constants calculated from the displacement curves were 0.9 10(-9) M, 0.6 10(-9) M, and 2 10(-9) M, respectively. Noninhibitory MAbs 13.29, 16.25, and 33.30 bound competitively with MAbs of group II but not with MAb 5.30 (group I). Monoclonal antibodies of group IV (MAbs 17.6, 18.1, 37.39, and 169.29) had no effect on activity and did not react with immobilized antigen. None of the MAbs reacted in ELISA with reduced and carboxymethylated human procolipase, indicating that epitopes involved conformationally dependent determinants on protein antigen. Anti-human colipase MAbs showed no cross-reactivity with porcine or equine procolipases. Monoclonal antibodies described here appear to be useful tools for studying surface hydrophobic domain of colipase and/or interaction between colipase and lipase in its active conformation (open lid).

Animals↗
PubMed2002

The triglyceride lipases of the pancreas.

Pancreatic triglyceride lipase (PTL) and its protein cofactor, colipase, are required for efficient dietary triglyceride digestion. In addition to PTL, pancreatic acinar cells synthesize two pancreatic lipase related proteins (PLRP1 and PLRP2), which have a high degree of sequence and structural homology with PTL. PLRP1 has no known activity. PTL and PLRP2 differ in substrate specificity, behavior in bile salts and dependence on colipase. Each protein has a globular amino-terminal (N-terminal) domain, which contains the catalytic site for PTL and PLRP2, and a beta-sandwich carboxyl-terminal (C-terminal) domain, which includes the predominant colipase-binding site for PTL. Inactive and active conformations of PTL have been described. They differ in the position of a surface loop, the lid domain, and of the beta5-loop. In the inactive conformation, the lid covers the active site and, upon activation by bile salt micelles and colipase or by lipid-water interfaces, the lid moves dramatically to open and configure the active site. After the lid movement, PTL and colipase create a large hydrophobic plateau that can interact with the lipid-water interface. A hydrophobic surface loop in the C-terminal domain, the beta5' loop, may also contribute to the interfacial-binding domain of the PTL-colipase complex.

Animals↗
PubMed2006

Pancreatic lipase and pancreatic lipase-related protein 2, but not pancreatic lipase-related protein 1, hydrolyze retinyl palmitate in physiological conditions.

The major sources of vitamin A in the human diet are retinyl esters (mainly retinyl palmitate) and provitamin A carotenoids. It has been shown that classical pancreatic lipase (PL) is involved in the luminal hydrolysis of retinyl palmitate (RP), but it is not known whether pancreatic lipase-related proteins 1 (PLRP1) and 2 (PLRP2), two other lipases recovered in the human pancreatic juice, are also involved. The aim of this study was to assess whether RP acts a substrate for these lipase-related proteins. Pure horse PL, horse PLRP2 and dog PLRP1 were incubated with RP solubilized in its physiological vehicles, i.e., triglyceride-rich lipid droplets, mixed micelles and vesicles. High performance liquid chromatography (HPLC) was used to assess RP hydrolysis by the free retinol released in the incubation medium. Incubation of RP-containing emulsions with horse PL and colipase resulted in RP hydrolysis (0.051+/-0.01 micromol/min/mg). This hydrolysis was abolished when colipase was not added to the medium. PLRP2 and PLRP1 were unable to hydrolyze RP solubilized in emulsions, regardless of whether colipase was added to the medium. PL hydrolyzed RP solubilized in mixed micelles as well (0.074+/-0.014 micromol/min/mg). Again, this hydrolysis was abolished in the absence of colipase. PLRP2 hydrolyzed RP solubilized in micelles but less efficiently than PL (0.023+/-0.005 micromol/min/mg). Colipase had no effect on this hydrolysis. PLRP1 was unable to hydrolyze RP solubilized in micelles, regardless of whether colipase was present or absent. Both PL and PLRP2 hydrolyzed RP solubilized in a vesicle rich-solution, and a synergic phenomenon between the two lipases was enlighten. Taken together, these results show that (1) PL hydrolyzes RP whether RP is solubilized in emulsions or in mixed micelles, (2) PLRP2 hydrolyzes RP only when RP is solubilized in mixed micelles, and (3) PLRP1 is unable to hydrolyze RP regardless of whether RP is solubilized in emulsions or in mixed micelles.

Animals↗
PubMed2001

Influence of intraduodenally infused olive and coconut oil on postprandial exocrine pancreatic secretions of growing pigs.

The effect of dietary vegetable oils differing in fatty acid composition that were infused directly into the duodenum on exocrine pancreatic secretions in pigs has not previously been studied. The objective of the present study was to determine the acute response of the exocrine pancreas to vegetable oils with various fatty acid profiles under prandial conditions. Six growing pigs (BW 13.2 kg) were surgically prepared with pancreatic duct catheters and duodenal reentrant T-cannulas. The animals were fed twice a day (1000 and 1600) a commercial weaner diet at a rate of 2% of BW. Beginning with the morning feeding, olive oil, coconut oil, or saline as a control were infused in boluses every 5 min in total 0.1% of BW over a period of 1 h directly into the duodenum according to a 3 x 3 Latin square design. Pancreatic juice was collected over a period of 4 h, beginning 1 h preprandially (0900) until 3 h postprandially (1300). A time effect was observed after the infusion of olive oil on the volume of secretion, on protein contents and outputs, as well as on lipase contents and outputs and on colipase contents. The infusion of saline and coconut oil changed the runs of the curves for lipase and colipase outputs. No time x treatment interactions were observed regarding volume of secretion, protein contents and outputs, trypsin contents and outputs, and lipase outputs. The runs of the curves for lipase contents were different between the olive oil and saline treatment and between the olive oil and coconut oil treatment. The runs of the curves for the olive oil and saline treatment differed from each other regarding colipase contents. Pooled values of colipase outputs were elevated after coconut oil treatment, and a positive correlation between trypsin and colipase contents was found. Under prandial conditions, the exocrine pancreas responds differently in its acute secretion to different vegetable oils due to the differences in the fatty acid profiles.

Animals↗
PubMed1980

Importance of phospholipids, pancreatic phospholipase A2, and fatty acid for the digestion of dietary fat: in vitro experiments with the porcine enzymes.

Long chain triglycerides emulsified with phospholipid are not directly available for hydrolysis by pancreatic lipase in vitro even in the presence of bile salts and colipase. The inhibition can be overcome by pancreatic phospholipase A2. There is a limited hydrolysis of the phospholipid during this period. The inhibition is explained by the finding that lipase does not bind to triglyceride emulsified by phospholipid but remains in the aqueous phase. A limited hydrolysis of the phospholipid by phospholipase A2 results in the binding of lipase to the substrate interface and a rapid rate of hydrolysis of the triglyceride. With time the inhibition of lipase activity can also be overcome by pancreatic lipase. A lag phase is seen before the accelerated hydrolysis of triglyceride reaches a high rate. The length of the lag phase is dependent on factors such as lipase and colipase concentration, pH, Ca++, and concentration of bile salt. During the lag phase no significant hydrolysis of phospholipid occurs. The primary factor is the binding of colipase to the substrate interface. Fatty acid present in the oil phase or produced from it by a limited hydrolysis of phospholipid by phospholipase A2 or triglyceride by lipase, changes the properties of the interface so that colipase can bind and thereby lipase via its binding to colipase. The milieu of small intestinal content favors the concerted action of several factors to make dietary triglyceride available for an effective hydrolysis by pancreatic lipase.

Animals↗
PubMed2003

Regulation of lipases by lipid-lipid interactions: implications for lipid-mediated signaling in cells.

Lipases are extracellular peripheral proteins that act at the surface of lipid emulsions stabilized, typically, by phospholipids. At a critical composition lipase activity toward substrates in phospholipid monolayers is discontinuously switched on by a small increase in substrate mole fraction. This occurs in part because lipase binding is inhibited by phospholipids. Binding of the lipase cofactor, colipase, is also inhibited by phospholipids. The initial rate of colipase binding increases abruptly at a substrate mole fraction that is approximately half the critical composition for lipase activity and just above that in substrate-phospholipid complexes. Moreover, complex collapse areas show an approximately 1:1 correlation with phospholipid excluded areas determined from an analysis of colipase adsorption rates. Thus, complexes inhibit colipase binding rate. Additionally, the switching of lipase activity likely occurs when uncomplexed substrate becomes the majority species in the interface. Lipase substrates, e.g. diacylglycerols, are typically the same lipids generated in the cytoplasmic surface of the plasma membrane of stimulated cells. As colipase binding is nonspecific and complexes involving lipase substrates form on the basis of lipid-lipid interactions alone, complexes should form in the plasma membrane of stimulated cells and may regulate protein translocation to the membrane.

Kinetics↗
PubMed1986

[The role of the N-terminal amino group in the activity of pancreatic lipase].

Chemical modification of porcine pancreatic lipase by increasing amounts of [2, 3-3H] succinic anhydride revealed the presence of two highly reactive amino groups in the enzyme. The initial modification of lipase with p-nitrophenyl acetate enabled practically selective modification of a single amino group in the enzyme molecule. The lipolytic activity of succinylated enzymes in micellar solution of sodium taurodeoxycholate in the presence of 10-fold excess of colipase was completely suppressed, and the monosuccinylated lipase did not bind to colipase-agarose column or to the surface of tributyrin emulsion in micellar solution of taurodeoxycholate in the presence of colipase. It was concluded that the N-terminal alpha-amino group of the enzyme is essential for lipase-colipase complex formation in true solution and for enzyme binding to the bile salt covered substrate surface in the presence of colipase.

Amino Acids↗