Substrate Report for: Tributyrin

ESTHER: Silvestrini_2020_Int.J.Biol.Macromol__
PubMedSearch: Silvestrini 2020 Int.J.Biol.Macromol
PubMedID: 32380114
Gene_locus related to this paper: canar-LipB
Inhibitor(s) related to this paper: Paraoxon

Abstract

Lipases (E.C. 3.1.1.3) are ubiquitous hydrolases for the carboxyl ester bond of water-insoluble substrates such as triacylglycerols and phospholipids. Candida antarctica Lipase B (CALB) acts in aqueous as well as in low-water media, thus being of considerable biochemical significance with high interest also for its industrial applications. The hydrolysis reaction follows a two-step mechanism, or 'interfacial activation', with adsorption of the enzyme to a heterogeneous interface and subsequent enhancement of the lipolytic activity. Once positioned within the catalytic triad, substrates are then hydrolysed, and products released. However, the intermediate steps of substrate transfer from the lipidic-aqueous phase to the enzyme surface and then down to the catalytic site are still unclear. By inhibiting CALB with ethyl phosphonate and incubating with glyceryl tributyrate (2,3-di (butanoyloxy) propyl butanoate), the crystal structure of the lipid-enzyme complex, at 1.55A resolution, shows the tributyrin in the limbus region of active site. The substrate is found 10A above the catalytic Ser, with the glycerol backbone pre-aligned for further processing by key interactions via an extended water network with alpha-helix10 and alpha-helix5. The findings offer new elements to elucidate the mechanism of substrate recognition, transfer and catalysis of Candida antarctica Lipase B (CALB) and lipases in general.

ESTHER: Moreau_1988_Biochim.Biophys.Acta_960_286
PubMedSearch: Moreau 1988 Biochim.Biophys.Acta 960 286
PubMedID: 3382677

Abstract

Rabbit gastric lipase was purified from an acetonic powder of rabbit stomach fundus. 25 mg of pure rabbit gastric lipase (glycerol ester hydrolase, EC 3.1.1.3) was obtained from 30 rabbit stomachs after ammonium sulfate fractionation, Sephadex G-100 gel filtration and cation exchange (mono S column) using a fast protein liquid chromatography (FPLC) system. The pure enzyme obtained was resistant to acidic pH conditions, and had specific activities of 1200, 850 and 280 U/mg, using, respectively, short- (tributyroylglycerol (TC4)), medium- (trioctanoyl- to tridecanoylglycerol (TC8-TC10)) and long-chain (soybean oil) triacylglycerols. The amino-acid composition was determined, and the first 30 N-terminal amino-acid residues were sequenced. Interfacial denaturation and catalytic properties on triacylglycerol emulsions were studied. Rabbit gastric lipase turned out to be structurally and kinetically very similar to human gastric lipase.

ESTHER: Gargouri_1986_Gastroenterology_91_919
PubMedSearch: Gargouri 1986 Gastroenterology 91 919
PubMedID: 3743968

Abstract

Under optimal conditions, assay for pure human gastric lipase was carried out with short- and long-chain triacylglycerol emulsions. Maximal specific activities of 1160 and 620 U/mg were obtained with tributyrin and soybean emulsion, respectively. We observed that with a tributyrin substrate, bovine serum albumin or bile salts must be added before the addition of the enzyme in order to prevent its irreversible interfacial denaturation. With long-chain triacylglycerols as substrate, a decrease with time in the rate of hydrolysis was associated with release of protonated long-chain fatty acids. The inhibitory effect of protonated fatty acids was also observed using tributyrin at pH 3.0. These observations support the conclusion that human gastric lipase shows no intrinsic specificity for short-chain triacylglycerols and that its apparent specificity is modulated by pH and presence of amphiphile in the incubation medium. Our conclusions support the view that, in the human, gastric lipolysis may play an important role in long-chain fat digestion.

ESTHER: Jung_2021_J.Biol.Eng_15_9
PubMedSearch: Jung 2021 J.Biol.Eng 15 9
PubMedID: 33676548

Abstract

Short-chain fatty acids, especially butyrate, play beneficial roles in sustaining gastrointestinal health. However, due to limitations associated with direct consumption of butyrate, there has been interest in using prodrugs of butyrate. Tributyrin (TB), a triglyceride composed of three butyrate molecules and a glycerol, is a well-studied precursor of butyrate. We screened a metagenome library consisting of 5760 bacterial artificial chromosome clones, with DNA inserts originating from mouse microbiomes, and identified two clones that efficiently hydrolyse TB into butyrate. Nucleotide sequence analysis indicated that inserts in these two clones are derived from unknown microbes. BLASTp analysis, however, revealed that each insert contains a gene homologous to acetylesterase or esterase genes, from Clostridium spp. and Bacteroides spp., respectively. Predicted structures of these two proteins both contain serine-histidine-aspartate catalytic triad, highly conserved in the family of esterases. Escherichia coli host expressing each of the two candidate genes invariably produced greater amounts of butyrate in the presence of TB. Importantly, administration of TB together with cloned E. coli cells alleviated inflammatory symptoms in a mouse model of acute colitis. Based on these results, we established an efficient on-site and real-time butyrate production system that releases butyrate in a controlled manner inside the intestine.

ESTHER: Silvestrini_2020_Int.J.Biol.Macromol__
PubMedSearch: Silvestrini 2020 Int.J.Biol.Macromol
PubMedID: 32380114
Gene_locus related to this paper: canar-LipB
Inhibitor(s) related to this paper: Paraoxon

Abstract

Lipases (E.C. 3.1.1.3) are ubiquitous hydrolases for the carboxyl ester bond of water-insoluble substrates such as triacylglycerols and phospholipids. Candida antarctica Lipase B (CALB) acts in aqueous as well as in low-water media, thus being of considerable biochemical significance with high interest also for its industrial applications. The hydrolysis reaction follows a two-step mechanism, or 'interfacial activation', with adsorption of the enzyme to a heterogeneous interface and subsequent enhancement of the lipolytic activity. Once positioned within the catalytic triad, substrates are then hydrolysed, and products released. However, the intermediate steps of substrate transfer from the lipidic-aqueous phase to the enzyme surface and then down to the catalytic site are still unclear. By inhibiting CALB with ethyl phosphonate and incubating with glyceryl tributyrate (2,3-di (butanoyloxy) propyl butanoate), the crystal structure of the lipid-enzyme complex, at 1.55A resolution, shows the tributyrin in the limbus region of active site. The substrate is found 10A above the catalytic Ser, with the glycerol backbone pre-aligned for further processing by key interactions via an extended water network with alpha-helix10 and alpha-helix5. The findings offer new elements to elucidate the mechanism of substrate recognition, transfer and catalysis of Candida antarctica Lipase B (CALB) and lipases in general.

ESTHER: Martinez-Martinez_2018_ACS.Chem.Biol_13_225
PubMedSearch: Martinez-Martinez 2018 ACS.Chem.Biol 13 225
PubMedID: 29182315
Gene_locus related to this paper: 9zzzz-a0a2k8jn75, 9zzzz-a0a2k8jt94, 9zzzz-a0a0g3fj44, 9zzzz-a0a0g3fh10, 9zzzz-a0a0g3fh03, 9bact-a0a1s5qkj8, 9zzzz-a0a0g3feh5, 9zzzz-a0a0g3fkz4, 9zzzz-a0a0g3fh07, 9zzzz-a0a0g3fh34, 9zzzz-a0a0g3fh31, 9bact-KY458167, alcbs-q0vqa3, 9bact-a0a1s5qki8, 9zzzz-a0a0g3feq8, 9zzzz-a0a0g3feh8, 9zzzz-a0a0g3fh19, 9bact-KY203037, 9bact-a0a1s5ql22, 9bact-a0a1s5qm34, 9bact-KY203034, 9bact-r9qzg0, 9bact-a0a1s5qly8, 9zzzz-a0a0g3fkz8, 9zzzz-a0a0g3feg9, 9zzzz-KY203033, 9zzzz-a0a0g3fes4, 9zzzz-a0a0g3fh42, 9bact-a0a1s5qlx2, 9zzzz-KY483651, 9bact-a0a1s5qmh4, 9zzzz-KY203032, 9zzzz-EH87, 9zzzz-a0a0g3fei1, 9zzzz-a0a0g3fet2, 9zzzz-KY483647, 9zzzz-EH82, 9zzzz-a0a0g3fe15, 9bact-KY203031, 9bact-t1w006, 9zzzz-a0a0g3fet6, 9bact-KY458164, geoth-g8myf3, 9bact-a0a1s5ql04, 9gamm-a0a1y0ihk7, 9bact-a0a1s5qly6, 9bact-a0a1s5qkg4, 9bact-a0a1s5qkm4, 9gamm-s5tv80, 9gamm-a0a0c4zhg2, 9zzzz-t1b379, 9gamm-KY483646, 9bact-KY458160, 9zzzz-a0a0g3fj57, 9gamm-s5t8349, 9arch-KY203036, 9bact-KY458168, 9zzzz-a0a0g3fes0, 9zzzz-t1be47, 9bact-KY458159, 9zzzz-a0a0g3fh39, 9bact-t1vzd5, 9prot-EH41, 9bact-Lip114, alcbs-q0vt77, 9bact-a0a1s5qke6, 9bact-a0a1s5qkf3, 9prot-SRP030024, 9gamm-s5t532, 9bact-a0a1s5qkl2, 9bact-a0a1s5qkk8, 9zzzz-KY203030, 9zzzz-t1d4I7, 9prot-KY019260, 9bact-a0a1s5qm38, 9arch-KY458161, 9prot-KY010302, 9zzzz-a0a0g3fl25, 9actn-KY010298, 9gamm-s5u059, 9bact-a0a1s5qmi7, 9bact-KY010297, 9bact-KY483642, 9bact-a0a1s5qkj1, 9bact-KY010299, 9bact-KY483648, alcbs-q0vtl7, 9bact-a0a1s5qf1, 9bact-a0a1s5qkg0, 9bact-a0a0h4tgu6, 9bact-MilE3, 9bact-LAE6, 9alte-MGS-MT1, 9bact-r9qzf7, 9gamm-k0c6t6, alcbs-q0vl36, alcbs-q0vlq1, alcbs-q0vq49, bacsu-pnbae, canar-LipB, canan-lipasA, geost-lipas, marav-a1u5n0, pseps-i7k8x5, staep-GEHD, symth-q67mr3, altma-s5cfn7, cycsp-k0c2b8, alcbs-q0vlk5, 9bact-k7qe48, 9bact-MGS-M1, 9bact-MGS-M2, 9bact-a0a0b5kns5, 9zzzz-a0a0g3fej4, 9zzzz-a0a0g3fj60, 9zzzz-a0a0g3fej0, 9zzzz-a0a0g3fj64, 9bact-a0a0b5kc16, 9zzzz-a0a0g3feg6, 9zzzz-a0a0g3feu6

Abstract

Esterases receive special attention because their wide distribution in biological systems and environments and their importance for physiology and chemical synthesis. The prediction of esterases substrate promiscuity level from sequence data and the molecular reasons why certain such enzymes are more promiscuous than others, remain to be elucidated. This limits the surveillance of the sequence space for esterases potentially leading to new versatile biocatalysts and new insights into their role in cellular function. Here we performed an extensive analysis of the substrate spectra of 145 phylogenetically and environmentally diverse microbial esterases, when tested with 96 diverse esters. We determined the primary factors shaping their substrate range by analyzing substrate range patterns in combination with structural analysis and protein-ligand simulations. We found a structural parameter that helps ranking (classifying) promiscuity level of esterases from sequence data at 94% accuracy. This parameter, the active site effective volume, exemplifies the topology of the catalytic environment by measuring the active site cavity volume corrected by the relative solvent accessible surface area (SASA) of the catalytic triad. Sequences encoding esterases with active site effective volumes (cavity volume/SASA) above a threshold show greater substrate spectra, which can be further extended in combination with phylogenetic data. This measure provides also a valuable tool for interrogating substrates capable of being converted. This measure, found to be transferred to phosphatases of the haloalkanoic acid dehalogenase superfamily and possibly other enzymatic systems, represents a powerful tool for low-cost bioprospecting for esterases with broad substrate ranges, in large scale sequence datasets.

ESTHER: Xiao_2015_J.Biol.Chem_290_28847
PubMedSearch: Xiao 2015 J.Biol.Chem 290 28847
PubMedID: 26494624
Gene_locus related to this paper: human-PNLIP, human-PNLIPRP2

Abstract

Pancreatic triglyceride lipase (PNLIP) is essential for dietary fat digestion in children and adults, whereas a homolog, pancreatic lipase-related protein 2 (PNLIPRP2), is critical in newborns. The two lipases are structurally similar, yet they have different substrate specificities. PNLIP only cleaves neutral fats. PNLIPRP2 cleaves neutral and polar fats. To test the hypothesis that the differences in activity between PNLIP and PNLIPRP2 are governed by surface loops around the active site, we created multiple chimeras of both lipases by exchanging the surface loops singly or in combination. The chimeras were expressed, purified, and tested for activity against various substrates. The structural determinants of PNLIPRP2 galactolipase activity were contained in the N-terminal domain. Of the surface loops tested, the lid domain and the beta5-loop influenced activity against triglycerides and galactolipids. Any chimera on PNLIP with the PNLIPRP2 lid domain or beta5-loop had decreased triglyceride lipase activity similar to that of PNLIPRP2. The corresponding chimeras of PNLIPRP2 did not increase activity against neutral lipids. Galactolipase activity was abolished by the PNLIP beta5-loop and decreased by the PNLIP lid domain. The source of the beta9-loop had minimal effect on activity. We conclude that the lid domain and beta5-loop contribute to substrate specificity but do not completely account for the differing activities of PNLIP and PNLIPRP2. Other regions in the N-terminal domain must contribute to the galactolipase activity of PNLIPRP2 through direct interactions with the substrate or by altering the conformation of the residues surrounding the hydrophilic cavity in PNLIPRP2.

ESTHER: Amara_2013_Eur.J.Lipid.Sci.Technol_115_442
PubMedSearch: Amara 2013 Eur.J.Lipid.Sci.Technol 115 442
Gene_locus related to this paper: bovin-balip, human-CEL

Abstract

Several well known microbial lipases were screened for their ability to hydrolyze synthetic medium chain monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). Fusarium solani cutinase and Thermomyces lanuginosus lipase (TLL) were found to hydrolyze MGDG at high rates (984 +/- 62 and 450 +/-41 U/mg, respectively). These activities remained however lower than those measured with pancreatic lipase-related protein 2 (PLRP2) on the same substrate. As previously observed with PLRP2, galactolipid-bile salt mixed micelles were found to be the best substrate form for microbial enzymes. The galactolipid to bile salt molar ratios for measuring maximum galactolipase activities were found to be similar to those previously established with PLRP2, suggesting that bile salts have mainly an effect on the substrate and not on the enzyme itself. The galactolipase activity of cutinase and TLL, as well as human and guinea pig PLRP2s were also measured using galactolipid monomolecular films. Enzymes having a lid (TLL and human PLRP2) were found to act at higher surface pressures than those with no lid (cutinase and guinea pig PLRP2). In silico docking of medium chain MGDG and DGDG in the active site of guinea pig PLRP2 and TLL reveals some structural analogies between these enzymes

ESTHER: Chahinian_2010_Biochim.Biophys.Acta_1801_1195
PubMedSearch: Chahinian 2010 Biochim.Biophys.Acta 1801 1195
PubMedID: 20655391

Abstract

To differentiate esterases from lipases at the structure-function level, we have compared the kinetic properties and structural features of sequence-related esterase 1 from rabbit liver (rLE) and bile-salt-activated lipase from bovine pancreas (bBAL). In contrast to rLE, bBAL hydrolyses water-insoluble medium and long chain esters as vinyl laurate, trioctanoin and olive oil. Conversely, rLE and bBAL are both active on water-soluble short chain esters as vinyl acetate, vinyl propionate, vinyl butyrate, tripropionin, tributyrin and p-nitrophenyl butyrate. However, the enzymes show distinctive kinetic behaviours. rLE displays maximal activity at low substrate concentration, below the critical micelle concentration, whereas bBAL acts preferencially on emulsified esters, at concentration exceeding the solubility limit. Comparison of the 3D structures of rLE and bBAL shows, in particular, that the peptide loop at positions 116-123 in bBAL is deleted in rLE. This peptide segment interacts with a bile salt molecule thus inducing a conformational transition which gives access to the active site. Inhibition studies and manual docking of a bulky ester molecule as vinyl laurate in the catalytic pocket of rLE and bBAL show that the inability of the esterase to hydrolyse large water-insoluble esters is not due to steric hindrance. It is hypothesized that esterases lack specific hydrophobic structures involved both in the stabilization of the lipase-lipid adsorption complex at interfaces and in the spontaneous transfer of a single substrate molecule from interface to the catalytic site.

ESTHER: Eydoux_2008_Biochemistry_47_9553
PubMedSearch: Eydoux 2008 Biochemistry 47 9553
PubMedID: 18702514
Gene_locus related to this paper: human-PNLIPRP2

Abstract

Access to the active site of pancreatic lipase (PL) is controlled by a surface loop, the lid, which normally undergoes conformational changes only upon addition of lipids or amphiphiles. Structures of PL with their lids in the open and functional conformation have required cocrystallization with amphiphiles. Here we report two crystal structures of wild-type and unglycosylated human pancreatic lipase-related protein 2 (HPLRP2) with the lid in an open conformation in the absence of amphiphiles. These structures solved independently are strikingly similar, with some residues of the lid being poorly defined in the electron-density map. The open conformation of the lid is however different from that previously observed in classical liganded PL, suggesting different kinetic properties for HPLRP2. Here we show that the HPLRP2 is directly inhibited by E600, does not present interfacial activation, and acts preferentially on substrates forming monomers or small aggregates (micelles) dispersed in solution like monoglycerides, phospholipids and galactolipids, whereas classical PL displays reverse properties and a high specificity for unsoluble substrates like triglycerides and diglycerides forming oil-in-water interfaces. These biochemical properties imply that the lid of HPLRP2 is likely to spontaneously adopt in solution the open conformation observed in the crystal structure. This open conformation generates a large cavity capable of accommodating the digalactose polar head of galactolipids, similar to that previously observed in the active site of the guinea pig PLRP2, but absent from the classical PL. Most of the structural and kinetic properties of HPLRP2 were found to be different from those of rat PLRP2, the structure of which was previously obtained with the lid in a closed conformation. Our findings illustrate the essential role of the lid in determining the substrate specificity and the mechanism of action of lipases.

ESTHER: Mancheno_2003_J.Mol.Biol_332_1059
PubMedSearch: Mancheno 2003 J.Mol.Biol 332 1059
PubMedID: 14499609
Gene_locus related to this paper: canru-2lipa

Abstract

The yeast Candida rugosa produces several closely related extracellular lipases that differ in their substrate specificity. Here, we report the crystal structure of the isoenzyme lipase 2 at 1.97A resolution in its closed conformation. Lipase 2 shows a 79.4% amino acid sequence identity with lipase 1 and 82.2% with lipase 3, which makes it relevant to compare these three isoenzymes. Despite this high level of sequence identity, structural comparisons reveal several amino acid changes affecting the flap (residue 69), the substrate-binding pocket (residues 127, 132 and 450) and the mouth of the hydrophobic tunnel (residues 296 and 344), which may be responsible for the different substrate specificity and catalytic properties of this group of enzymes. Also, these comparisons reveal two distinct regions in the hydrophobic tunnel: a phenylalanyl-rich region and an aliphatic-rich region. Whereas this last region is essentially identical in the three isoenzymes, the phenylalanyl content in the first one is specific for each lipase, resulting in a different environment of the catalytic triad residues, which probably tunes finely their lipase/esterase character. The greater structural similarity observed between the monomeric form of lipase 3 and lipase 2 concerning the above-mentioned key residues led us to propose a significant esterase activity for this last protein. This enzymatic activity has been confirmed with biochemical experiments using cholesteryl [1-14C]oleate as substrate. Surprisingly, lipase 2 is a more efficient esterase than lipase 3, showing a twofold specific activity against cholesteryl [1-14C]oleate in our experimental conditions. These results show that subtle amino acid changes within a highly conserved protein fold may produce protein variants endowed with new enzymatic properties.

ESTHER: Eggert_2000_Eur.J.Biochem_267_6459
PubMedSearch: Eggert 2000 Eur.J.Biochem 267 6459
PubMedID: 11029590
Gene_locus related to this paper: bacsu-LIPB

Abstract

A novel gene lipB, which encodes an extracellular lipolytic enzyme, was identified in the Bacillus subtilis genomic DNA sequence. We have cloned and overexpressed lipB in B. subtilis and Escherichia coli and have also purified the enzyme from a B. subtilis culture supernatant to electrophoretic homogeneity. Four different lipase assays were used to determine its catalytic activity: pH-stat, spectrophotometry, fluorimetry and the monomolecular film technique. LipB preferentially hydrolysed triacylglycerol-esters and p-nitrophenyl-esters of fatty acids with short chain lengths of <= 10 carbon atoms. Triolein, which is a typical substrate for true lipases, was not hydrolysed at all. These results led us to classify LipB as an esterase rather than a lipase. The catalytic triad of LipB consists of residues Ser78, Asp134, and His157 as demonstrated by amino-acid sequence alignments and site-directed mutagenesis. The nucleophile Ser78 is located in a lipase-specific consensus sequence, which is Ala-X-Ser-X-Gly for most Bacillus lipases. All other bacterial lipases contain a glycine residue instead of the alanine at position-2 with respect to the catalytic serine. We have investigated the role of this alanine residue by constructing LipB variant A76G, thereby restoring the lipase-specific consensus motif. When compared with LipB this variant showed a markedly reduced thermostability but an increased stability at pH 5-7. Determination of the specific activities of wild-type LipB and variant A76G using a monomolecular film of the substrate monoolein revealed an interesting result: the A76G substitution had converted the esterase LipB into a monoacylglycerol hydrolase.

ESTHER: Oh_1999_FEMS.Microbiol.Lett_179_385
PubMedSearch: Oh 1999 FEMS.Microbiol.Lett 179 385
PubMedID: 10518741
Gene_locus related to this paper: staha-Q9RGZ6

Abstract

Lipase of Staphylococcus haemolyticus L62 was purified from culture supernatant and its molecular mass was estimated to be 45 kDa by SDS-PAGE. Its optimum temperature and pH for the hydrolysis of olive oil was 28 degrees C and pH 8.5, respectively. The enzyme was stable up to 50 degrees C in the presence of Ca(2+)and over the pH range 5-11. It had high hydrolytic activity against tributyrin, tripropionin, and trimyristin among various triglycerides. The gene encoding the lipase was cloned in Escherichia coli. Sequence analysis showed an open reading frame of 2136 bp, which encodes a preproenzyme of 711 amino acids. The preproenzyme is composed of a signal peptide (60 aa), a pro-peptide (259 aa), and a mature enzyme (392 aa). The mature enzyme has 49-67% amino acid sequence homology with other staphylococcal lipases.

ESTHER: Carriere_1991_Eur.J.Biochem_202_75
PubMedSearch: Carriere 1991 Eur.J.Biochem 202 75
PubMedID: 1935982
Gene_locus related to this paper: canfa-1lipg

Abstract

A lipase was found to be present in dog stomach which appeared to be more abundant in the fundic than in the pyloric mucosa. Dog gastric lipase was extracted by soaking the gastric tissue and further purified after cation exchange, anion exchange and gel-filtration using fast protein liquid chromatography. The amino-acid composition, N-terminal amino-acid sequence, substrate specificity, interfacial and kinetic behavior and inactivation by sulfhydryl reagents were determined and compared with those of human and rabbit gastric lipases. We report for the first time that a gastric lipase is 13 times more active on long-chain than on short-chain triacylglycerols at pH 4.0, reaching a maximal specific activity of 950 U/mg on Intralipide emulsion.

ESTHER: Moreau_1988_Biochim.Biophys.Acta_960_286
PubMedSearch: Moreau 1988 Biochim.Biophys.Acta 960 286
PubMedID: 3382677

Abstract

Rabbit gastric lipase was purified from an acetonic powder of rabbit stomach fundus. 25 mg of pure rabbit gastric lipase (glycerol ester hydrolase, EC 3.1.1.3) was obtained from 30 rabbit stomachs after ammonium sulfate fractionation, Sephadex G-100 gel filtration and cation exchange (mono S column) using a fast protein liquid chromatography (FPLC) system. The pure enzyme obtained was resistant to acidic pH conditions, and had specific activities of 1200, 850 and 280 U/mg, using, respectively, short- (tributyroylglycerol (TC4)), medium- (trioctanoyl- to tridecanoylglycerol (TC8-TC10)) and long-chain (soybean oil) triacylglycerols. The amino-acid composition was determined, and the first 30 N-terminal amino-acid residues were sequenced. Interfacial denaturation and catalytic properties on triacylglycerol emulsions were studied. Rabbit gastric lipase turned out to be structurally and kinetically very similar to human gastric lipase.

ESTHER: Gargouri_1986_Gastroenterology_91_919
PubMedSearch: Gargouri 1986 Gastroenterology 91 919
PubMedID: 3743968

Abstract

Under optimal conditions, assay for pure human gastric lipase was carried out with short- and long-chain triacylglycerol emulsions. Maximal specific activities of 1160 and 620 U/mg were obtained with tributyrin and soybean emulsion, respectively. We observed that with a tributyrin substrate, bovine serum albumin or bile salts must be added before the addition of the enzyme in order to prevent its irreversible interfacial denaturation. With long-chain triacylglycerols as substrate, a decrease with time in the rate of hydrolysis was associated with release of protonated long-chain fatty acids. The inhibitory effect of protonated fatty acids was also observed using tributyrin at pH 3.0. These observations support the conclusion that human gastric lipase shows no intrinsic specificity for short-chain triacylglycerols and that its apparent specificity is modulated by pH and presence of amphiphile in the incubation medium. Our conclusions support the view that, in the human, gastric lipolysis may play an important role in long-chain fat digestion.