Porcine pancreatic lipase. Completion of the primary structure

Effectiveness of a New Enzyme-Free Method for the Preparation of a Decellularized Adipose-Derived Matrix

BACKGROUND

Decellularized adipose-derived matrix (DAM) represents a new alternative to tissue fillers. The function of DAM is closely associated with the decellularization technique used for its preparation. However, most techniques are time-consuming and expensive, and this might reduce the popularity of DAM.

OBJECTIVES

The study aimed to investigate an enzyme-free adipose decellularization method and generate a DAM capable of adipose tissue regeneration.

METHODS

DAMs prepared by the enzyme-free and Flynn's methods were compared and co-cultured with human adipose-derived stem cells (hADSCs) to investigate cytocompatibility. Adipose tissue formation was evaluated by injecting the DAMs into the backs of nude mice over 4 weeks. Samples were harvested for gross and perilipin immunohistochemistry analysis at 1 and 4 weeks.

RESULTS

The enzyme-free method is effective for adipose decellularization because it removes adipocytes and preserves the microstructure. In vitro, the DAM made by the enzyme-free method could support the attachment, growth, proliferation, and differentiation of hADSCs, and promote the enhanced secretion of vascular endothelial growth factor by hADSCs; this DAM also induced the formation and maturity of adipocytes in vivo.

CONCLUSIONS

This study describes a highly effective enzyme-free method for adipose tissue decellularization that also promotes adipocyte formation and adipose tissue volume stability in vitro and in vivo, resulting in a new alternative tissue filler.

Discovery of arginine-containing tripeptides as a new class of pancreatic lipase inhibitors

Aim: The inhibition of pancreatic lipase (PL) represents one of the most promising strategies in the search for novel antiobesity drugs. We propose here a pioneering course by exploring tripeptide scaffolds in the way to selective PL inhibitors. Methodology/Results: The peptide series exhibited good PL inhibitory properties in vitro, with all the strongest inhibitors sharing a central arginine, shown in silico to be relevant for the active site-directed activity. The compounds were found devoid of inhibitory properties on acetylcholinesterase. Conclusion: Present results disclosed that basic tripeptides are able to interact efficiently with the PL-binding pocket, where they adopt a binding pose suitable for functional-to-inhibition interactions with key amino acids. Main inhibitor MALA4 may be selected as lead for further optimization.

Biochemical characterization, cloning and molecular modeling of a digestive lipase from red seabream (Pagrus major): Structural explanation of the interaction deficiency with colipase and lipidic interface

Red seabream digestive lipase (RsDL) was purified from fresh pyloric caeca. Pure RsDL has an apparent molecular mass of 50 kDa. The RsDL is more active on short-chain triacylglycerols (TC₄), and enzymatic activity decreases when medium (TC₈) or long-chain (olive oil) triacylglycerols were used as substrates. The specific activities of RsDL are very weak as compared to those obtained with classical pancreatic lipases. No colipase was detected in the red seabream pyloric caeca. Furthermore, the RsDL was not activated by a mammal colipase. Similar results were reported for annular seabream lipase. In order to explain structurally the discrepancies between sparidae and mammal lipases, genes encoding mature RsDL and five other lipases from sparidae fish species were cloned and sequenced. Phylogenetic studies indicated the closest homology of sparidae lipases to bird pancreatic ones. Structural models were built for annular seabream and RsDL under their closed and open forms using mammal pancreatic lipases as templates. Several differences were noticed when analyzing the amino acids corresponding to those involved in HPL binding to colipase. This is likely to prevent interaction between the fish lipase and the mammalian colipase and may explain the fact that mammalian colipase is not effective in activating sparidae lipases. In addition, several hydrophobic residues, playing a key role in anchoring pancreatic lipase onto the lipid interface, are replaced by polar residues in fish lipases. This might explain the reason why the latter enzymes display weak activity levels when compared to mammalian pancreatic lipases.

Partial optimization of the 5-terminal codon increased a recombination porcine pancreatic lipase (opPPL) expression in Pichia pastoris

Pancreatic lipase plays a key role in intestinal digestion of feed fat, and is often deficient in young animals such as weaning piglets. The objective of this study was to express and characterize a partial codon optimized porcine pancreatic lipase (opPPL). A 537 bp cDNA fragment encoding N-terminus amino acid residue of the mature porcine pancreatic lipase was synthesized according to the codon bias of Pichia pastoris and ligated to the full-length porcine pancreatic lipase cDNA fragment. The codon optimized PPL was cloned into the pPICZαA (Invitrogen, Beijing, China) vector. After the resultant opPPL/pPICZαΑ plasmid was transformed into P.pastoris, the over-expressed extracellular opPPL containing a His-tag to the C terminus was purified using Ni Sepharose affinity column (GE Healthcare, Piscataway, NJ, USA), and was characterized against the native enzyme (commercial PPL from porcine pancreas, Sigma). The opPPL exhibited a molecular mass of approximately 52 kDa, and showed optimal temperature (40°C), optimal pH (8.0), K_m (0.041 mM), and V_max (2.008 µmol.mg protein ⁻¹.min⁻¹) similar to those of the commercial enzyme with p-NPP as the substrate. The recombinant enzyme was stable at 60°C, but lost 80% (P<0.05) of its activity after exposure to heat ≥60°C for 20 min. The codon optimization increased opPPL yield for ca 4 folds (146 mg.L⁻¹ vs 36 mg.L⁻¹) and total enzyme activity increased about 5 folds (1900 IU.L⁻¹ vs 367 IU.L⁻¹) compared with those native naPPL/pPICZαΑ tranformant. Comparison of gene copies and mRNA profiles between the two strains indicated the increased rePPL yields may partly be ascribed to the increased protein translational efficiency after codon optimization. In conclusion, we successfully optimized 5-terminal of porcine pancreatic lipase encoding gene and over-expressed the gene in P. pastoris as an extracellular, functional enzyme. The recombination enzyme demonstrates a potential for future use as an animal feed additive for animal improvement.

Inhibitory activity of chlorogenic acids in decaffeinated green coffee beans against porcine pancreas lipase and effect of a decaffeinated green coffee bean extract on an emulsion of olive oil

A decaffeinated green coffee bean extract (DGCBE) inhibited porcine pancreas lipase (PPL) activity with an IC50 value of 1.98 mg/mL. Six different chlorogenic acids in DGCBE contributed to this PPL inhibition, accounting for 91.8% of the inhibitory activity. DGCBE increased the droplet size and decreased the specific surface area of an olive oil emulsion.

Application of porcine lipase secreted by pichia pastoris to improve fat digestion and growth performance of postweaning piglets

The aim of the study was to use Pichia pastoris to express a recombinant porcine lipase gene (pLip). The expression-secretion cassette was constructed using the P. pastoris GAPDH (glyceraldehyde-3-phosphate-dehydrogenase) promoter and an 89-residue prepro-alpha-factor secretion signal fused to the AOX1 terminator (the pGAPZalphaA vector). A total of 1,408 bp of pancreatic lipase cDNA was produced, which was located from the position of 4-nt upstream of ATG to 1408-nt inside the intact coding region of the pLip sequence. In an animal trial, three concentrations of recombinant lipase activity (0, 5,000 and 10,000 U/kg) were blended with the basal diet and fed to weaned piglets for six weeks. During the experimental period, the growth performance (bodyweight, feed intake, and feed efficiency) of the test groups was superior to that of the control group (p < 0.05). Furthermore, the group fed the diet blended with 10,000 U/kg of recombinant lipase showed significant (p < 0.05) increases in blood triglyceride (TG) concentration on the seventh day postweaning. These results suggested that the porcine lipase protein yielded by transformed yeast cells may improve fat digestibility and enhance the growth performance in postweaning piglets.

Purification and characterization of the first reptile pancreatic lipase: the turtle

OBJECTIVES

The aim of the present study was to purify and characterize classic pancreatic lipase from the reptile turtle (TuPL).

METHODS

The lipase was purified from the fresh pancreas extract followed by diethylamino ethyl-cellulose chromatography, Sephacryl S-200 gel filtration, and a Mono-Q Sepharose chromatography.

RESULTS

Turtle pancreatic lipase is a serine enzyme and it contains only 1 free cysteine. Its activity is maximum at pH 8.2 and 37 degrees C. A specific activity of 10.000 U/mg and 5.000 U/mg were measured titrimetrically on tributyrin and olive oil emulsion, respectively. Natural detergents act as potent inhibitors of TuPL, and colipase restores the activity. When the lipase is inhibited by synthetic detergent, simultaneous addition of colipase and bile salts is required to restore the TuPL activity. The critical surface pressure of TuPL (pi(c)) = 20.9 mN m(-1)) is similar to the one of human PL (pi(c) = 18 mN m(-1)).

CONCLUSIONS

The results presented in this article indicate that despite the primitive character of the turtle, no significant difference has been observed between TuPL and known mammalian PLs. However, partial proteolysis of TuPL with chymotrypsin shows the absence of the 14-kDa fragment identified as the C-terminal domain in the case of many classic PLs.

Modification of Porcine Pancreatic Lipase with Z‐Proline

Porcine pancreatic lipase was modified with Z-proline via the constitution of amide bonds between the free amino groups of lipase and the carboxyl groups of Z-proline, which were activated by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). Different amounts of Z-proline were bound to lipase. Modification degree was determined by 2,4,6-trinitrobenzene sulphonic acid (TNBS), by means of the decrease in free amino groups on lipase. The reason for choosing Z-proline was its unique structural characteristics, protected amino groups, and its effect on protein conformation by reducing the flexibility of the lipase molecule, thus achieving stabilization against changes in pH and temperature. After the modification, porcine pancreatic lipase was found to have new physicochemical characteristics, such as optimum alkaline pH stability and thermal stability at elevated temperatures.

Regulation of cholesteryl ester hydrolases

Recent developments in understanding the biochemical and molecular nature of the CE hydrolases and their impact on cellular cholesterol trafficking have further defined the enzyme's mechanism of action with reasonable clarity. The availability of the cDNA probe for the human lysosomal acid lipase/CE hydrolase and the hormone-sensitive lipase now makes it possible to study CE hydrolase gene regulation and expression in human tissue; and it can now be stated with more assurance that the cytoplasmic CE hydrolase (NCEH) is most likely activated through phosphorylation by the cyclic AMP-dependent protein kinase. Evidence also shows that the NCEH is most likely identical to the hormone-sensitive lipase and that it plays an important role in cholesterol efflux properties of the cell. Recent advances in the discovery of the role of the eicosanoid/cytokine network in the regulation of CE hydrolysis, highlighted in Figure 10, further emphasize the interesting but complex nature of the cholesterol trafficking processes in cells, particularly under pathophysiological conditions such as cell injury, repair, and inflammation. It can be speculated that in several years, when the crystal structure of the CE hydrolase is known, the structure-function properties of this enzyme's catalytic domain, as it relates to the physical state of the CE substrates, should further clarify the precise role of this enzyme in intracellular cholesterol mobilization and trafficking under a variety of cellular conditions.

Cloning and molecular modelling of turkey pancreatic lipase: structural explanation of the increased interaction power with lipidic interface

Starting from total pancreatic mRNAs, turkey pancreatic lipase (TPL) cDNA was synthesized by RT-PCR and cloned into the PGEM-T vector. Amino acid sequence of the TPL is compared to that of human pancreatic lipase (HPL). A 3-D structure model of TPL was built using the 3-D structure of HPL as template, given the high amino acid sequence homology between the two lipases. Based on this model, the enhanced interaction power of TPL, as compared to that of HPL, into a phosphatidylcholine monolayer film, could be explained. We concluded that an increase in the exposed hydrophobic residues on the surface of TPL would be responsible for an enhanced interaction with a lipidic interface.

Biochemical characterization, cloning, and molecular modelling of chicken pancreatic lipase

Chicken pancreatic lipase (CPL) was purified from delipidated pancreas. Pure CPL was obtained after ammonium sulphate fractionation, then DEAE-cellulose, Sephacryl S-200 gel filtration, and FPLC Mono-Q Sepharose columns. The pure lipase is a glycosylated monomer having a molecular mass of about 50kDa. The 23 N-terminal amino acid residues of CPL were sequenced. The sequence is similar to those of avian and mammalian pancreatic lipases. CPL presents the interfacial activation phenomenon tested with tripropionin or vinyl ester. When CPL was inhibited by synthetic detergent (TX-100) or amphipathic protein (BSA), simultaneous addition of bile salts and colipase was required to restore the full CPL activity. In the absence of colipase and bile salts, CPL was unable to hydrolyse tributyrin emulsion. This enzyme can tolerate, more efficiently than HPL, the accumulation of long-chain free fatty acids at the interface when olive oil emulsion was used as substrate in the absence of bile salts and colipase. The CPL activity, under these conditions, was linear whereas that of HPL decreased rapidly. Anti-TPL polyclonal antibodies cross-reacted specifically with CPL. The gene encoding the mature CPL was cloned and sequenced. The deduced amino acid sequence of the mature lipase shows a high degree of homology with the mammalian pancreatic lipases. A 3D structure model of CPL was built using the HPL structure as template. We have concluded that a slight increase in the exposed hydrophobic residues on the surface of CPL, as compared to HPL, could be responsible for a higher tolerance to the presence of long-chain free fatty acids at the lipid/water interface.

The lipase gene family

Development of the lipase gene family spans the change in science that witnessed the birth of contemporary techniques of molecular biology. Amino acid sequencing of enzymes gave way to cDNA cloning and gene organization, augmented by in vitro expression systems and crystallization. This review traces the origins and highlights the functional significance of the lipase gene family, overlaid on the background of this technical revolution. The gene family initially consisted of three mammalian lipases [pancreatic lipase (PL), lipoprotein lipase, and hepatic lipase] based on amino acid sequence similarity and gene organization. Family size increased when several proteins were subsequently added based on amino acid homology, including PL-related proteins 1 and 2, phosphatidylserine phospholipase A1, and endothelial lipase. The physiological function of each of the members is discussed as well as the region responsible for lipase properties such as enzymatic activity, substrate binding, heparin binding, and cofactor interaction. Crystallization of several lipase gene family members established that the family belongs to a superfamily of enzymes, which includes esterases and thioesterases. This superfamily is related by tertiary structure, rather than amino acid sequence, and represents one of the most populous families found in nature.

From interaction of lipidic vehicles with intestinal epithelial cell membranes to the formation and secretion of chylomicrons

Lipophilic drugs are carried by chylomicrons that are secreted by the small intestine and transported in lymph. This review discusses the digestion, uptake, and transport of dietary lipids and the impact that these processes have on the absorption of lipophilic drugs by the gastrointestinal tract. This chapter complements Dr. Chris Potter's chapter on the "pre-absorptive" events of drug processing and solubilization. This chapter reviews the digestion of lipids in the gastric and intestinal lumen and the role of bile salts in the solubilization of lipid digestion products for uptake by the gut. Both the passive and active uptake of lipid digestion products is discussed. How intestinal lipid transporters located at the brush border membrane may play a role in the uptake of lipids by the enterocytes is examined, as is the regulation of the absorption of cholesterol by the human ATP-binding cassette transporter-1 (ABC1). The intracellular trafficking and the resynthesis of complex lipids from lipid digestion products are explored, and the formation and secretion of chylomicrons are described.

Characterization of turkey pancreatic lipase

Turkey pancreatic lipase (TPL) was purified from delipidated pancreases. Pure TPL (glycerol ester hydrolase, EC 3.1.1.3) was obtained after ammonium sulfate fractionation, Sephacryl S-200 gel filtration, anion exchange chromatography (DEAE-Sepharose) and size exclusion column using high performance liquid chromatography system (HPLC). The pure lipase, which is not a glycoprotein, was presented as a monomer having a molecular mass of about 45 kDa. The lipase activity was maximal at pH 8.5 and 37 degrees C. TPL hydrolyses the long chains triacylglycerols more efficiently than the short ones. A specific activity of 4300 U/mg was measured on triolein as substrate at 37 degrees C and at pH 8.5 in the presence of colipase and 4 mM NaTDC. This enzyme presents the interfacial activation when using tripropionin as substrate. TPL was inactivated when the enzyme was incubated at 65 degrees C or at pH less than 5. Natural detergent (NaTDC), synthetic detergent (Tween-20) or amphipatic protein (beta-lactoglobulin A) act as potent inhibitors of TPL activity. To restore the lipase activity inhibited by NaTDC, colipase should be added to the hydrolysis system. When lipase is inhibited by synthetic detergent or protein, simultaneous addition of colipase and NaTDC was required to restore the TPL activity. The first 22 N-terminal amino acid residues were sequenced. This sequence was similar to those of mammal's pancreatic lipases. The biochemical properties of pancreatic lipase isolated from bird are similar to those of mammals.

Human pancreatic lipase: an exposed hydrophobic loop from the C-terminal domain may contribute to interfacial binding

Epitope mapping was performed using four anti-HPL monoclonal antibodies (mAb's 81-23, 146-40, 315-25, and 320-24) directed against human pancreatic lipase (HPL). Three HPL mutants produced in insect cells were tested for this purpose: (i) N-HPL, which consists of only the N-terminal domain of HPL, (ii) HPL(-lid), in which a short loop consisting of 5 amino acid residues replaces the full-length 23-residue lid domain present in HPL, and (iii) N-GPLRP2/C-HPL chimera, a chimeric mutant consisting of the N-terminal domain of the guinea pig pancreatic lipase related protein 2 (GPLRP2) fused to the C-terminal domain of HPL. The C-terminal domain of HPL (C-HPL) was prepared in a pure form after performing chymotryptic digestion of HPL. The mAb 146-40 recognizes HPL, HPL(-lid), and N-HPL but not GPLRP2, N-GPLRP2/C-HPL chimera, or the C-HPL. The antibody mAb 146-40 therefore specifically recognizes the N-terminal domain of HPL, and the epitope recognized does not include the amphiphilic lid. On the other hand, mAb's 81-23, 315-25, and 320-24 react specifically to the C-terminal domain of HPL, since they recognize HPL, HPL(-lid), the N-GPLRP2/C-HPL chimera, and the C-HPL but not N-HPL or GPLRP2. It was further established that these three mAb's recognize the same conformational epitope, the structure of which is stabilized by the N-terminal domain in the presence of SDS at concentrations greater than its critical micellar concentration. This conformational epitope was found to be located in the vicinity of Met 397 and Arg 414. These two residues delineate a highly exposed peptide stretch extending from the HPL C-terminal domain, which includes a hydrophobic surface loop (beta5'). Kinetic studies on the HPL/mAb's complexes showed that the lipase activity was much lower in these complexes than in HPL. The results of the present study suggest for the first time that the beta5' loop from the C-terminal domain may be involved in the interaction of HPL with a lipid/water interface.

Lipase activation by nonionic detergents. The crystal structure of the porcine lipase-colipase-tetraethylene glycol monooctyl ether complex

The crystal structure of the ternary porcine lipase-colipase-tetra ethylene glycol monooctyl ether (TGME) complex has been determined at 2.8 A resolution. The crystals belong to the cubic space group F23 with a = 289.1 A and display a strong pseudo-symmetry corresponding to a P23 lattice. Unexpectedly, the crystalline two-domain lipase is found in its open configuration. This indicates that in the presence of colipase, pure micelles of the nonionic detergent TGME are able to activate the enzyme; a process that includes the movement of an N-terminal domain loop (the flap). The effects of TGME and colipase have been confirmed by chemical modification of the active site serine residue using diisopropyl p-nitrophenylphosphate (E600). In addition, the presence of a TGME molecule tightly bound to the active site pocket shows that TGME acts as a substrate analog, thus possibly explaining the inhibitory effect of this nonionic detergent on emulsified substrate hydrolysis at submicellar concentrations. A comparison of the lipase-colipase interactions between our porcine complex and the human-porcine complex (van Tilbeurgh, H., Egloff, M.-P., Martinez, C., Rugani, N., Verger, R., and Cambillau, C.(1993) Nature 362, 814-820) indicates that except for one salt bridge interaction, they are conserved. Analysis of the superimposed complexes shows a 5.4 degrees rotation on the relative position of the N-terminal domains excepting the flap that moves in a concerted fashion with the C-terminal domain. This flexibility may be important for the binding of the complex to the water-lipid interface.

Chicken lecithin-cholesterol acyltransferase. Molecular characterization reveals unusual structure and expression pattern

Rapidly growing oocytes in the laying hen are, in addition to the liver, targets of the so-called "reverse cholesterol transport" (RCT) (Vieira, P.M., Vieira, A.V., Sanders, E.J., Steyrer, E., Nimpf, J., and Schneider, W.J. (1995) J. Lipid Res. 36, 601-610), pointing to the importance of this process in nonplacental reproduction. We have begun to delineate the details of this unique transport pathway branch by molecular characterization of the first nonmammalian lecithin-cholesterol acyltransferase (LCAT), the enzyme that catalyzes an early step in RCT. The biological significance of the enzyme is underscored by the high degree of protein sequence identity (73%) maintained from chicken to man. Interestingly, the conservation extends much less to the cysteine residues; in fact, two of the cysteines thought to be important in mammalian enzymes (residues 31 and 184 in man) are absent from the chicken enzyme, providing proof of their dispensability for enzymatic activity. Antibodies prepared against a chicken LCAT fusion protein cross-react with human LCAT and identify a 64-kDa protein present in enzymatically active fractions obtained by hydrophobic chromatography of chicken serum. The developmental and tissue distribution pattern of LCAT in females is striking; during embryogenesis and adolescence, LCAT expression is extremely high in liver but undetectable in brain. Upon onset of laying, however, brain LCAT mRNA increases suddenly and is maintained at levels 5 times higher than in liver, in stark contrast to most mammals. In adult roosters, the levels of LCAT transcripts in brain are lower than in liver. Together with the molecular characterization of chicken LCAT, these newly discovered developmental changes and gender differences in its expression establish the avian oocyte/liver system as a powerful model to delineate in vivo regulatory elements of RCT.

Lipase structures at the interface between chemistry and biochemistry

In this chapter we review recent molecular knowledge on two structurally related mammalian triglyceride lipases which have evolved from a common ancestral gene. The common property of the lipase family members is that they interact with non-polar substances. Pancreatic lipase hydrolyzes triglycerides in the small intestine in the presence of many dietary components, other digestive enzymes and high concentrations of detergents (bile salts). Lipoprotein lipase acts at the vascular side of the blood vessels where it hydrolyses triglycerides and some phospholipids of the circulating plasma lipoproteins. A third member of the gene family, hepatic lipase, is found in the liver of mammals. Also, this lipase is involved in lipoprotein metabolism. The three lipases are distantly related to some non-catalytic yolk proteins from Drosophila (Persson et al., 1989; Kirchgessner et al., 1989; Hide et al., 1992) and to a phospholipase A1 from hornet venom (Soldatova et al., 1993).

Tryptic cleavage of gastric lipases: location of the single disulfide bridge

Human (HGL) and rabbit (RGL) gastric lipases were cleaved by trypsin and the resulting peptides were characterized. Exposure of HGL to trypsin led to the production of three identified fragments (H1, H2 and H3) resulting from cleavage sites at Lys-4 and Arg-229. Fragments H2 (Lys-4-Arg-229) and H3 (Glu-230-Lys-379) were derived from fragment H1 (Lys-4-Lys-379). The single disulfide bridge (Cys-236-Cys-244) of the molecule is localized in fragment H3. Out of the three cysteine residues conserved in all known gastric lipases, the free sulfhydryl group (Cys-227) was localized in fragment H2. Immunoblots, carried out with the tryptic fragments of HGL and anti-HGL mAbs, revealed that five inhibitory mAbs immunoreacted selectively with the N-terminal fragment H2, whereas two other non inhibitory mAbs immunoreacted exclusively with the C-terminal fragment H3. Trypsin also cleaved RGL at two sites (Arg-55 and Arg-229) leading to four identifiable fragments (R1, R2, R3 and R4). One cleavage site (Arg-229) was found to be identical in both RGL and HGL. We propose that this latter site is localized between the two domains of native gastric lipases.

Dromedary pancreatic lipase: purification and structural properties

Dromedary pancreatic lipase was purified from delipidated pancreases. Pure dromedary pancreatic lipase (glycerol ester hydrolase, EC 3.1.1.3) was obtained after ammonium sulfate fractionation, Sephadex G-100 gel filtration, anion-exchange (Mono Q Sepharose) and size exclusion column using high performance liquid chromatography (HPLC). The pure lipase is a monomer and has a molecular mass of about 45 kD and a pI of around 4.8. A specific activity of 5900 U/mg was measured on tributyrin as substrate at 37 degrees C in the presence of colipase and 2 mM NaTDC. The first 11 N-terminal amino acid residues and 10 peptides obtained by endoproteinase Glu-C digestion were sequenced. Dromedary pancreatic lipase is very similar to other pancreatic lipases as compared with their N-terminal and some peptides sequences. DrPL is activated by interfaces. The interfacial activation could be related to the presence of a lid and in fact one fragment of this lid domain (P9) was sequenced here: its' role will be discussed below.

The lipA gene of Serratia marcescens which encodes an extracellular lipase having no N-terminal signal peptide

The lipA gene encoding an extracellular lipase was cloned from the wild-type strain of Serratia marcescens Sr41. Nucleotide sequencing showed a major open reading frame encoding a 64.9-kDa protein of 613 amino acid residues; the deduced amino acid sequence contains a lipase consensus sequence, GXSXG. The lipase had 66 and 56% homologies with the lipases of Pseudomonas fluorescens B52 and P. fluorescens SIK W1, respectively, but did not show any overall homology with lipases from other origins. The Escherichia coli cells carrying the S. marcescens lipA gene did not secrete the lipase into the medium. The S. marcescens lipase had no conventional N-terminal signal sequence but was also not subjected to any processing at both the N-terminal and C-terminal regions. A specific short region similar to the regions of secretory proteins having no N-terminal signal peptide was observed in the amino acid sequence. Expression of the lipA gene in S. marcescens was affected by the carbon source and the addition of Tween 80.

Cloning of the classical guinea pig pancreatic lipase and comparison with the lipase related protein 2

Starting from total pancreatic mRNAs, the classical guinea pig pancreatic lipase was cloned using rapid amplification of 3' and 5' cDNA ends. Internal oligonucleotide primers were designed from a partial cDNA clone including the region coding for the lid domain. Using this strategy, we did not amplify the cDNA corresponding to the pancreatic lipase related protein 2 in which the lid domain is deleted. Amino acid sequences of the classical guinea pig pancreatic lipase and the related protein 2 were compared based on the primary and tertiary structures of the classical human pancreatic lipase. Their distinct physiological roles are discussed in the light of functional amino acid differences.

Purification of human gastric lipase by immunoaffinity and quantification of this enzyme in the duodenal contents using a new ELISA procedure

Human gastric lipase (HGL) is the first lipolytic enzyme involved in the digestion of dietary lipids along the gastrointestinal tract. We describe an improved procedure for isolating the enzyme using immunoaffinity chromatography in combination with ion-exchange chromatography. The purified enzyme, showing a single band on SDS-PAGE, expressed a specific activity of 1000 U/mg using tributyrin as the substrate. We also describe a specific enzyme-linked immunosorbent assay (ELISA) procedure for measuring duodenal HGL levels. The ELISA was performed using an anti-HGL polyclonal antibody (pAb) as the captor antibody and a biotinylated monoclonal antibody (mAb) as the detector antibody. With the double sandwich ELISA technique, HGL in the range of 1-60 ng/ml was measured in less than 5 h. Identical HGL concentrations were obtained using the above ELISA procedure when compared to those based on the enzymatic activity using the potentiometric method (correlation coefficient: r = 0.95). No significant interference from other duodenal components was observed, as proved by the quantitative HGL determinations performed on intestinal samples.

A structural domain (the lid) found in pancreatic lipases is absent in the guinea pig (phospho)lipase

Typically pancreatic lipases are characterized by the following properties: (1) they are activated by lipid/water interfaces (interfacial activation), (2) they are inhibited by bile salts but reactivated by colipase (a small activator protein), and (3) they do not hydrolyze significantly phospholipids. A cDNA clone encoding a guinea pig pancreatic (phospho)lipase (GPL) has been sequenced and expressed. The enzyme (recombinant as well as native) differs from other pancreatic lipases in that (1) it is not interfacially activated, (2) its activity is unaffected by the presence of bile salts and/or colipase using tributyrin as substrate, and (3) it exhibits equally phospholipase A1 and lipase activities. The amino acid sequence of GPL is highly homologous to that of other known pancreatic lipases, with the exception of a deletion in the so-called lid domain that regulates access to the active centers of other lipases. We propose that this deletion is directly responsible for the anomalous behavior of this enzyme. Thus GPL challenges the classical distinction between lipases, esterases, and phospholipases.

Chymotryptic cleavage of lipoprotein lipase. Identification of cleavage sites and functional studies of the truncated molecule

Treatment of bovine lipoprotein lipase (LPL) with chymotrypsin results in cleavage between residues Phe390-Ser391 and between Trp392-Ser393, indicating that this region is exposed in the native conformation of LPL. Two main fragments are generated, one large including the amino-terminus (chymotrypsin-truncated LPL = c-LPL) and one small, carboxy-terminal fragment. The small fragment is not stable, but is further degraded by the protease. Isolated c-LPL has full catalytic activity against tributyryl glycerol (tributyrin) and p-nitrophenyl butyrate, while the activity against emulsions of long-chain triacylglycerols and against liposomes is reduced and the activity against milk fat globules and chylomicrons is lost. Several properties of c-LPL were investigated. It was found that c-LPL interacts with apolipoprotein CII (apo CII) as efficiently as intact LPL. The truncated enzyme bound to liposomes and to emulsions of long-chain triacylglycerols as well as the intact enzyme did. In contrast, c-LPL did not bind to milk fat globules or to chylomicrons. The activity of c-LPL was more sensitive to inhibition by other lipid-binding proteins, e.g. apolipoprotein CIII (apo CIII), than was the intact enzyme. The affinity for heparin was as high with c-LPL as with intact LPL. Like intact LPL, c-LPL is dimeric in its active form, as evidenced by sucrose density gradient centrifugation. It is concluded that the reduced catalytic and lipid-binding properties of c-LPL compared with intact LPL are related to the properties of the substrate interface. It is speculated that the carboxy-terminal part of LPL contains a secondary lipid-binding site, which is important for activity against chylomicrons and related substrates.

Epitope mapping and immunoinactivation of human gastric lipase using five monoclonal antibodies

Five monoclonal antibodies (mAb) directed against human gastric lipase (HGL) have been produced by hybridization of myeloma cells with spleen cells of BALB/c immunized mice. All these mAb belong to the IgG1 class with a kappa light chain. The effects of these mAb on the enzymic activity of HGL were studied and used to define three classes of antibodies, depending upon their immunoinactivation properties. As determined by ELISA and immunoinactivation studies, four overlapping epitopes were found to be part of the functional sites of the enzyme. The mAb appear to be suitable probes for studying the lipid binding and catalytic domains of HGL. The results of the ELISA additivity test were used to describe tentatively the epitopes of HGL in terms of a schematic spatial map.

News from the interface: the molecular structures of triacylglyceride lipases

Neutral lipases constitute one of the most ubiquitous and diverse families of enzymes. The recently solved crystal structures of three lipases show that enzymatic hydrolysis occurs with the assistance of a catalytic triad, which is structurally reminiscent of serine proteinases. However, these lipases only become active at the oil-water interface through a conformational change that exposes the active centre of the enzyme.