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Cassidy BM, Zino S, Fjeld K, Molven A, Lowe ME, Xiao X. Single nucleotide polymorphisms in CEL-HYB1 increase risk for chronic pancreatitis through proteotoxic misfolding. Hum Mutat 2020; 41:1967-1978. [PMID: 32906201 DOI: 10.1002/humu.24105] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 08/19/2020] [Accepted: 08/28/2020] [Indexed: 12/20/2022]
Abstract
Genetic variants contribute to the risk of chronic pancreatitis (CP) in adults and children. The risk variant CEL-HYB1, a recombinant hybrid allele of CEL and its neighboring pseudogene (CELP), encodes a pathogenic variant of the pancreatic digestive enzyme carboxyl ester lipase (CEL). We previously identified combinations of two non-synonymous SNPs, c.1463T>C (p. Ile488Thr) and c.1643C>T (p. Thr548Ile), in the break point region of CEL-HYB1. Herein, we tested whether these missense variants alter CP risk and their impact on functional properties of the CEL-HYB1 protein. Examination of CEL-HYB1 haplotypes in European patients and controls revealed that the combinationThr488-Ile548 was present only in cases (p ≤ .001). The lipase activity of purified recombinant CEL-HYB1 variants showed normal or near normal activity. CEL-HYB variants expressed in HEK293T cells all had decreased secretion compared with CEL, formed intracellular protein aggregates, and triggered endoplasmic reticulum stress. Thus, we propose that the presence of missense variants in CEL-HYB increases the pathogenicity of CEL-HYB1 through misfolding and gain-of-function proteotoxicity. Interestingly, Thr488-Ile548 and Thr488-Thr548 were equally pathogenic in the functional assays even though only the Thr488-Ile548 haplotype was significantly enriched in cases. The explanation for the mismatch between genetic and functional data requires further investigation.
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Affiliation(s)
- Brett M Cassidy
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Sammy Zino
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Karianne Fjeld
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway.,Department of Medical Genetics, Haukeland University Hospital, Bergen, Norway
| | - Anders Molven
- The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen, Bergen, Norway.,Department of Pathology, Haukeland University Hospital, Bergen, Norway
| | - Mark E Lowe
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Xunjun Xiao
- Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri, USA
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Sahaka M, Amara S, Wattanakul J, Gedi MA, Aldai N, Parsiegla G, Lecomte J, Christeller JT, Gray D, Gontero B, Villeneuve P, Carrière F. The digestion of galactolipids and its ubiquitous function in Nature for the uptake of the essential α-linolenic acid. Food Funct 2020; 11:6710-6744. [PMID: 32687132 DOI: 10.1039/d0fo01040e] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Galactolipids, mainly monogalactosyl diglycerides and digalactosyl diglycerides are the main lipids found in the membranes of plants, algae and photosynthetic microorganisms like microalgae and cyanobacteria. As such, they are the main lipids present at the surface of earth. They may represent up to 80% of the fatty acid stocks, including a large proportion of polyunsaturated fatty acids mainly α-linolenic acid (ALA). Nevertheless, the interest in these lipids for nutrition and other applications remains overlooked, probably because they are dispersed in the biomass and are not as easy to extract as vegetable oils from oleaginous fruit and oil seeds. Another reason is that galactolipids only represent a small fraction of the acylglycerolipids present in modern human diet. In herbivores such as horses, fish and folivorous insects, galactolipids may however represent the main source of dietary fatty acids due to their dietary habits and digestion physiology. The development of galactolipase assays has led to the identification and characterization of the enzymes involved in the digestion of galactolipids in the gastrointestinal tract, as well as by microorganisms. Pancreatic lipase-related protein 2 (PLRP2) has been identified as an important factor of galactolipid digestion in humans, together with pancreatic carboxyl ester hydrolase (CEH). The levels of PLRP2 are particularly high in monogastric herbivores thus highlighting the peculiar role of PLRP2 in the digestion of plant lipids. Similarly, pancreatic lipase homologs are found to be expressed in the midgut of folivorous insects, in which a high galactolipase activity can be measured. In fish, however, CEH is the main galactolipase involved. This review discusses the origins and fatty acid composition of galactolipids and the physiological contribution of galactolipid digestion in various species. This overlooked aspect of lipid digestion ensures not only the intake of ALA from its main natural source, but also the main lipid source of energy for growth of some herbivorous species.
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Affiliation(s)
- Moulay Sahaka
- Aix Marseille Univ, CNRS, UMR7281 Bioénergétique et Ingénierie des Protéines, 31 Chemin Joseph Aiguier, 13009 Marseille, France.
| | - Sawsan Amara
- Lipolytech, Zone Luminy Biotech, 163 avenue de Luminy, 13288 Marseille Cedex 09, France
| | - Jutarat Wattanakul
- Division of Food, Nutrition and Dietetics, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK
| | - Mohamed A Gedi
- Division of Food, Nutrition and Dietetics, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK
| | - Noelia Aldai
- Lactiker Research Group, Department of Pharmacy & Food Sciences, University of the Basque Country (UPV/EHU), 01006 Vitoria-Gasteiz, Spain
| | - Goetz Parsiegla
- Aix Marseille Univ, CNRS, UMR7281 Bioénergétique et Ingénierie des Protéines, 31 Chemin Joseph Aiguier, 13009 Marseille, France.
| | | | - John T Christeller
- The New Zealand Institute for Plant and Food Research Ltd (Plant & Food Research), Palmerston North Research Centre, Palmerston North, New Zealand
| | - David Gray
- Division of Food, Nutrition and Dietetics, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire, LE12 5RD, UK
| | - Brigitte Gontero
- Aix Marseille Univ, CNRS, UMR7281 Bioénergétique et Ingénierie des Protéines, 31 Chemin Joseph Aiguier, 13009 Marseille, France.
| | | | - Frédéric Carrière
- Aix Marseille Univ, CNRS, UMR7281 Bioénergétique et Ingénierie des Protéines, 31 Chemin Joseph Aiguier, 13009 Marseille, France.
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Salhi A, Amara S, Mansuelle P, Puppo R, Lebrun R, Gontero B, Aloulou A, Carrière F. Characterization of all the lipolytic activities in pancreatin and comparison with porcine and human pancreatic juices. Biochimie 2020; 169:106-120. [DOI: 10.1016/j.biochi.2019.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 07/04/2019] [Indexed: 10/26/2022]
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Structure of the lipoprotein lipase-GPIHBP1 complex that mediates plasma triglyceride hydrolysis. Proc Natl Acad Sci U S A 2018; 116:1723-1732. [PMID: 30559189 PMCID: PMC6358717 DOI: 10.1073/pnas.1817984116] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Lipoprotein lipase (LPL) is responsible for the intravascular processing of triglyceride-rich lipoproteins. The LPL within capillaries is bound to GPIHBP1, an endothelial cell protein with a three-fingered LU domain and an N-terminal intrinsically disordered acidic domain. Loss-of-function mutations in LPL or GPIHBP1 cause severe hypertriglyceridemia (chylomicronemia), but structures for LPL and GPIHBP1 have remained elusive. Inspired by our recent discovery that GPIHBP1's acidic domain preserves LPL structure and activity, we crystallized an LPL-GPIHBP1 complex and solved its structure. GPIHBP1's LU domain binds to LPL's C-terminal domain, largely by hydrophobic interactions. Analysis of electrostatic surfaces revealed that LPL contains a large basic patch spanning its N- and C-terminal domains. GPIHBP1's acidic domain was not defined in the electron density map but was positioned to interact with LPL's large basic patch, providing a likely explanation for how GPIHBP1 stabilizes LPL. The LPL-GPIHBP1 structure provides insights into mutations causing chylomicronemia.
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Touvrey C, Courageux C, Guillon V, Terreux R, Nachon F, Brazzolotto X. X-ray structures of human bile-salt activated lipase conjugated to nerve agents surrogates. Toxicology 2018; 411:15-23. [PMID: 30359675 DOI: 10.1016/j.tox.2018.10.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 10/06/2018] [Accepted: 10/20/2018] [Indexed: 01/19/2023]
Abstract
The efficiency of human butyrylcholinesterase (BChE) as a stoichiometric bioscavenger of nerve agents is well established. However, wide use is currently limited by production and purification costs. Aiming at identifying an alternative human protein bioscavenger, we looked for an original scaffold candidate by virtual screening of the Protein Data Bank for functional similarity using the "Surfing the Molecules" software (sumo-pbil.ibcp.fr) and a search model based on the BChE active site topology. Besides the expected acetylcholinesterase and butyrylcholinesterase, we identified a set of bile salt activated lipases structures, among which the human pancreatic lipase (hBAL) that shares 34% identity with BChE. We produced the recombinant enzyme in mammalian cells, purified it, and measured the inhibition constants for paraoxon and surrogates of VX, sarin and tabun. We solved the X-ray structure of apo hBAL and conjugates with paraoxon and the surrogates at resolutions in the 2-Å range. These structures allow the assessment of hBAL for scavenging nerve agents. They revealed that hBAL has inverted stereoselectivity for the surrogates of nerve agent compared to human cholinesterases. We observed a remarkable flip of the catalytic histidine driven by the chelation of Zn2+. Dealkylation of the conjugate, aka aging, was solely observed for paraoxon.
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Affiliation(s)
- Cédric Touvrey
- Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, 69367 Lyon Cedex 07, France
| | - Charlotte Courageux
- Institut de Recherche Biomédicale des Armées, Département de Toxicologie et Risques Chimiques, Brétigny sur Orge, 91220, France
| | - Virginia Guillon
- Institut de Recherche Biomédicale des Armées, Département de Toxicologie et Risques Chimiques, Brétigny sur Orge, 91220, France
| | - Raphael Terreux
- Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, 69367 Lyon Cedex 07, France
| | - Florian Nachon
- Institut de Recherche Biomédicale des Armées, Département de Toxicologie et Risques Chimiques, Brétigny sur Orge, 91220, France.
| | - Xavier Brazzolotto
- Institut de Recherche Biomédicale des Armées, Département de Toxicologie et Risques Chimiques, Brétigny sur Orge, 91220, France
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de Gelder S, Sæle Ø, de Veen BTH, Vos J, Flik G, Berntssen MHG, Klaren PHM. The polycyclic aromatic hydrocarbons benzo[a]pyrene and phenanthrene inhibit intestinal lipase activity in rainbow trout (Oncorhynchus mykiss). Comp Biochem Physiol C Toxicol Pharmacol 2017; 198:1-8. [PMID: 28476648 DOI: 10.1016/j.cbpc.2017.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Revised: 04/18/2017] [Accepted: 04/25/2017] [Indexed: 11/26/2022]
Abstract
Elevated levels of polycyclic aromatic hydrocarbons (PAHs) are detected in aquafeeds where fish oils are (partially) replaced by vegetable oils. The highly lipophilic PAHs solubilize readily in oil droplets and micelles in the intestinal lumen that can affect enzymatic lipid digestion by altering lipase activity. We therefore investigated the effect of two PAHs, benzo[a]pyrene (BaP) and phenanthrene (PHE), on bile salt-activated lipase (BAL) activity in desalted luminal extracts of the proximal intestine of rainbow trout (Oncorhynchus mykiss) using the triacylglycerides rapeseed oil and fish oil as substrates. The hydrolysis of rapeseed oil and fish oil measured at a calculated substrate concentration of 2.2mM, increased linearly up to 30min at 15°C. Substrate dependency under initial velocity conditions was described by simple Michaelis-Menten kinetics with a Km value of 1.2mM for rapeseed and fish oil. Rapeseed oil hydrolysis was inhibited by 1nM BaP and 10nM PHE. The hydrolysis of fish oil was only inhibited by 10μM BaP. The in vitro lipase activity data were corroborated by TLC/HPLC analysis of the reaction products, showing that in the presence of BaP and PHE, 46-80% less free fatty acids (FFA) were hydrolysed from rapeseed and fish oil triacylglycerides. The presence of low concentrations of BaP and PHE decreased rapeseed oil hydrolysis by BAL whereas fish oil hydrolysis was not affected. The replacement of fish oil by rapeseed oil in aquafeeds introduces PAHs that could affect lipid digestion.
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Affiliation(s)
- Stefan de Gelder
- Radboud University, Institute for Water and Wetland Research, Department of Animal Ecology and Physiology, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands; National Institute of Nutrition and Seafood Research, P.O. Box 2029, Nordnes, 5817 Bergen, Norway.
| | - Øystein Sæle
- National Institute of Nutrition and Seafood Research, P.O. Box 2029, Nordnes, 5817 Bergen, Norway
| | - Bas T H de Veen
- Radboud University, Institute for Water and Wetland Research, Department of Animal Ecology and Physiology, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
| | - Joëlle Vos
- Radboud University, Institute for Water and Wetland Research, Department of Animal Ecology and Physiology, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
| | - Gert Flik
- Radboud University, Institute for Water and Wetland Research, Department of Animal Ecology and Physiology, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
| | - Marc H G Berntssen
- National Institute of Nutrition and Seafood Research, P.O. Box 2029, Nordnes, 5817 Bergen, Norway
| | - Peter H M Klaren
- Radboud University, Institute for Water and Wetland Research, Department of Animal Ecology and Physiology, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
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Khan FI, Lan D, Durrani R, Huan W, Zhao Z, Wang Y. The Lid Domain in Lipases: Structural and Functional Determinant of Enzymatic Properties. Front Bioeng Biotechnol 2017; 5:16. [PMID: 28337436 PMCID: PMC5343024 DOI: 10.3389/fbioe.2017.00016] [Citation(s) in RCA: 198] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 02/22/2017] [Indexed: 01/08/2023] Open
Abstract
Lipases are important industrial enzymes. Most of the lipases operate at lipid–water interfaces enabled by a mobile lid domain located over the active site. Lid protects the active site and hence responsible for catalytic activity. In pure aqueous media, the lid is predominantly closed, whereas in the presence of a hydrophobic layer, it is partially opened. Hence, the lid controls the enzyme activity. In the present review, we have classified lipases into different groups based on the structure of lid domains. It has been observed that thermostable lipases contain larger lid domains with two or more helices, whereas mesophilic lipases tend to have smaller lids in the form of a loop or a helix. Recent developments in lipase engineering addressing the lid regions are critically reviewed here. After on, the dramatic changes in substrate selectivity, activity, and thermostability have been reported. Furthermore, improved computational models can now rationalize these observations by relating it to the mobility of the lid domain. In this contribution, we summarized and critically evaluated the most recent developments in experimental and computational research on lipase lids.
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Affiliation(s)
- Faez Iqbal Khan
- School of Food Science and Engineering, South China University of Technology, Guangzhou, China; School of Chemistry and Chemical Engineering, Henan University of Technology, Zhengzhou, China
| | - Dongming Lan
- School of Food Science and Engineering, South China University of Technology , Guangzhou , China
| | - Rabia Durrani
- School of Bioscience and Bioengineering, South China University of Technology , Guangzhou , China
| | - Weiqian Huan
- School of Bioscience and Bioengineering, South China University of Technology , Guangzhou , China
| | - Zexin Zhao
- School of Bioscience and Bioengineering, South China University of Technology , Guangzhou , China
| | - Yonghua Wang
- School of Food Science and Engineering, South China University of Technology , Guangzhou , China
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8
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Xiao X, Jones G, Sevilla WA, Stolz DB, Magee KE, Haughney M, Mukherjee A, Wang Y, Lowe ME. A Carboxyl Ester Lipase (CEL) Mutant Causes Chronic Pancreatitis by Forming Intracellular Aggregates That Activate Apoptosis. J Biol Chem 2016; 291:23224-23236. [PMID: 27650499 DOI: 10.1074/jbc.m116.734384] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Indexed: 12/23/2022] Open
Abstract
Patients with chronic pancreatitis (CP) frequently have genetic risk factors for disease. Many of the identified genes have been connected to trypsinogen activation or trypsin inactivation. The description of CP in patients with mutations in the variable number of tandem repeat (VNTR) domain of carboxyl ester lipase (CEL) presents an opportunity to study the pathogenesis of CP independently of trypsin pathways. We tested the hypothesis that a deletion and frameshift mutation (C563fsX673) in the CEL VNTR causes CP through proteotoxic gain-of-function activation of maladaptive cell signaling pathways including cell death pathways. HEK293 or AR42J cells were transfected with constructs expressing CEL with 14 repeats in the VNTR (CEL14R) or C563fsX673 CEL (CEL maturity onset diabetes of youth with a deletion mutation in the VNTR (MODY)). In both cell types, CEL MODY formed intracellular aggregates. Secretion of CEL MODY was decreased compared with that of CEL14R. Expression of CEL MODY increased endoplasmic reticulum stress, activated the unfolded protein response, and caused cell death by apoptosis. Our results demonstrate that disorders of protein homeostasis can lead to CP and suggest that novel therapies to decrease the intracellular accumulation of misfolded protein may be successful in some patients with CP.
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Affiliation(s)
- Xunjun Xiao
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Gabrielle Jones
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Wednesday A Sevilla
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Donna B Stolz
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
| | - Kelsey E Magee
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Margaret Haughney
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Amitava Mukherjee
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Yan Wang
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
| | - Mark E Lowe
- From the Department of Pediatrics, Children's Hospital of Pittsburgh at University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15224 and
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9
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John S, Thangapandian S, Lee KW. Potential human cholesterol esterase inhibitor design: benefits from the molecular dynamics simulations and pharmacophore modeling studies. J Biomol Struct Dyn 2012; 29:921-36. [PMID: 22292952 DOI: 10.1080/07391102.2012.10507419] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Human pancreatic cholesterol esterase (hCEase) is one of the lipases found to involve in the digestion of large and broad spectrum of substrates including triglycerides, phospholipids, cholesteryl esters, etc. The presence of bile salts is found to be very important for the activation of hCEase. Molecular dynamic simulations were performed for the apoform and bile salt complexed form of hCEase using the co-ordinates of two bile salts from bovine CEase. The stability of the systems throughout the simulation time was checked and two representative structures from the highly populated regions were selected using cluster analysis. These two representative structures were used in pharmacophore model generation. The generated pharmacophore models were validated and used in database screening. The screened hits were refined for their drug-like properties based on Lipinski's rule of five and ADMET properties. The drug-like compounds were further refined by molecular docking simulation using GOLD program based on the GOLD fitness score, mode of binding, and molecular interactions with the active site amino acids. Finally, three hits of novel scaffolds were selected as potential leads to be used in novel and potent hCEase inhibitor design. The stability of binding modes and molecular interactions of these final hits were re-assured by molecular dynamics simulations.
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Affiliation(s)
- Shalini John
- Division of Applied Life Science_(BK21 Program), Systems and Synthetic Agrobiotech Center (SSAC) Gyeongsang National University (GNU), 501 Jinju-daero, Gazha-dong, Jinju 660-701, Republic of Korea
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10
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Understanding the lipid-digestion processes in the GI tract before designing lipid-based drug-delivery systems. Ther Deliv 2012; 3:105-24. [PMID: 22833936 DOI: 10.4155/tde.11.138] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Many of the compounds present in lipid-based drug-delivery systems are esters, such as acylglycerols, phospholipids, polyethyleneglycol mono- and di-esters and polysorbate, which can be hydrolyzed by the various lipolytic enzymes present in the GI tract. Lipolysis of these compounds, along with dietary fats, affects the solubility, dispersion and bioavailibity of poorly water-soluble drugs. Pharmaceutical scientists have been taking a new interest in fat digestion in this context, and several studies presenting in vitro gastrointestinal lipolysis models have been published. In most models, it is generally assumed that pancreatic lipase is the main enzyme involved in the gastrointestinal lipolysis of lipid formulations. It was established, however, that gastric lipase, pancreatic carboxyl ester hydrolaze and pancreatic lipase-related protein 2 are the major players involved in the lipolysis of lipid excipients containing acylglycerols and polyethyleneglycol esters. These findings have shown that the lipolysis of lipid excipients may actually start in the stomach and involve several lipolytic enzymes. These findings should therefore be taken into account when testing in vitro the dispersion and bioavailability of poorly water-soluble drugs formulated with lipids. In this review, we present the latest data available about the lipolytic enzymes involved in gastrointestinal lipolysis and suggest tracks for designing physiologically relevant in vitro digestion models.
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Abstract
Lipases are ubiquitous enzymes, widespread in nature. They were first isolated from bacteria in the early nineteenth century and the associated research continuously increased due to the particular characteristics of these enzymes. This chapter reviews the main sources, structural properties, and industrial applications of these highly studied enzymes.
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Affiliation(s)
- Leticia Casas-Godoy
- Equipe de Catalyse et Ingénierie Moléculaire Enzymatique, Laboratoire d'Ingénierie des Systèmes Biologiques et Procédés, Université de Toulouse, INSA, UPS, INP, LISBP, Toulouse, France
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12
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Kurtovic I, Marshall SN, Zhao X. Hydrophobic immobilization of a bile salt activated lipase from Chinook salmon (Oncorhynchus tshawytscha). ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.molcatb.2011.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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13
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Chahinian H, Fantini J, Garmy N, Manco G, Sarda L. Non-lipolytic and lipolytic sequence-related carboxylesterases: A comparative study of the structure–function relationships of rabbit liver esterase 1 and bovine pancreatic bile-salt-activated lipase. Biochim Biophys Acta Mol Cell Biol Lipids 2010; 1801:1195-204. [DOI: 10.1016/j.bbalip.2010.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Revised: 07/07/2010] [Accepted: 07/09/2010] [Indexed: 10/19/2022]
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14
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15
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Lipolysis of the semi-solid self-emulsifying excipient Gelucire® 44/14 by digestive lipases. Biochim Biophys Acta Mol Cell Biol Lipids 2008; 1781:367-75. [DOI: 10.1016/j.bbalip.2008.05.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2008] [Revised: 05/19/2008] [Accepted: 05/20/2008] [Indexed: 11/20/2022]
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16
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Maeda A, Mizuno T, Bunya M, Sugihara S, Nakayama D, Tsunasawa S, Hirota Y, Sugihara A. Characterization of novel cholesterol esterase from Trichoderma sp. AS59 with high ability to synthesize steryl esters. J Biosci Bioeng 2008; 105:341-9. [DOI: 10.1263/jbb.105.341] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 01/07/2008] [Indexed: 11/17/2022]
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17
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Gherardini PF, Wass MN, Helmer-Citterich M, Sternberg MJE. Convergent Evolution of Enzyme Active Sites Is not a Rare Phenomenon. J Mol Biol 2007; 372:817-45. [PMID: 17681532 DOI: 10.1016/j.jmb.2007.06.017] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Revised: 05/14/2007] [Accepted: 06/08/2007] [Indexed: 02/03/2023]
Abstract
Since convergent evolution of enzyme active sites was first identified in serine proteases, other individual instances of this phenomenon have been documented. However, a systematic analysis assessing the frequency of this phenomenon across enzyme space is still lacking. This work uses the Query3d structural comparison algorithm to integrate for the first time detailed knowledge about catalytic residues, available through the Catalytic Site Atlas (CSA), with the evolutionary information provided by the Structural Classification of Proteins (SCOP) database. This study considers two modes of convergent evolution: (i) mechanistic analogues which are enzymes that use the same mechanism to perform related, but possibly different, reactions (considered here as sharing the first three digits of the EC number); and (ii) transformational analogues which catalyse exactly the same reaction (identical EC numbers), but may use different mechanisms. Mechanistic analogues were identified in 15% (26 out of 169) of the three-digit EC groups considered, showing that this phenomenon is not rare. Furthermore 11 of these groups also contain transformational analogues. The catalytic triad is the most widespread active site; the results of the structural comparison show that this mechanism, or variations thereof, is present in 23 superfamilies. Transformational analogues were identified for 45 of the 951 four-digit EC numbers present within the CSA and about half of these were also mechanistic analogues exhibiting convergence of their active sites. This analysis has also been extended to the whole Protein Data Bank to provide a complete and manually curated list of the all the transformational analogues whose structure is classified in SCOP. The results of this work show that the phenomenon of convergent evolution is not rare, especially when considering large enzymatic families.
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Affiliation(s)
- Pier Federico Gherardini
- Biochemistry Building, Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK
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Fernandez S, Jannin V, Rodier JD, Ritter N, Mahler B, Carrière F. Comparative study on digestive lipase activities on the self emulsifying excipient Labrasol®, medium chain glycerides and PEG esters. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:633-40. [PMID: 17418634 DOI: 10.1016/j.bbalip.2007.02.009] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 02/22/2007] [Accepted: 02/26/2007] [Indexed: 11/22/2022]
Abstract
Labrasol is a lipid-based self-emulsifying excipient used in the preparation of lipophilic drugs intended for oral delivery. It is mainly composed of PEG esters and glycerides with medium acyl chains, which are potential substrates for digestive lipases. The hydrolysis of Labrasol by porcine pancreatic extracts, human pancreatic juice and several purified digestive lipases was investigated in the present study. Classical human pancreatic lipase (HPL) and porcine pancreatic lipase, which are the main lipases involved in the digestion of dietary triglycerides, showed very low levels of activity on the entire Labrasol excipient as well as on separated fractions of glycerides and PEG esters. On the other hand, gastric lipase, pancreatic lipase-related protein 2 (PLRP2) and carboxyl ester hydrolase (CEH) showed high specific activities on Labrasol. These lipases were found to hydrolyze the main components of Labrasol (PEG esters and monoglycerides) used as individual substrates, whereas these esters were found to be poor substrates for HPL. The lipolytic activity of pancreatic extracts and human pancreatic juice on Labrasol(R) is therefore mainly due to the combined action of CEH and PLRP2. These two pancreatic enzymes, together with gastric lipase, are probably the main enzymes involved in the in vivo lipolysis of Labrasol taken orally.
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Affiliation(s)
- Sylvie Fernandez
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, CNRS UPR 9025, 31 chemin Joseph Aiguier, 13402 Marseille cedex 20, France
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19
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Abstract
PURPOSE OF REVIEW The review evaluates current knowledge of the different lipases catalyzing triglyceride lipolysis in the human digestive tract, focusing on their mode of action - information useful for developing strategies to regulate the bioavailability of fatty acid. RECENT FINDINGS Optimal levels of digestive lipases promote efficient triglyceride lipolysis in healthy humans. Management of fatty acid bioavailability during pancreatic insufficiencies, however, requires enzyme replacement therapy. Such therapy entails gastro-protected porcine pancreatic powder, associated with antacid treatment when duodenal pH is too acidic; recently, enteric-coated high-buffered pancrelipase or recombinant gastric lipase have been used. Another promising strategy is to focus on lipid substrate to optimize lipid-water interface properties. Research on obesity treatment focuses on inhibitors. Orlistat is the first inhibitor to be used extensively. Others treatments are in development, including human pancreatic lipase C-terminal, polyphenols, specific proteins and peptides; however, their relevance has not yet been tested in humans. SUMMARY A better knowledge of lipase structure and mode of action will help the development of new natural inhibitors with fewer secondary effects. More intensive research in protein engineering for recombinant lipase production and in clinical nutrition, together with careful evaluation of patients' individual needs is necessary.
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Affiliation(s)
- Martine Armand
- INSERM, U476 'Nutrition Humaine et Lipides', INRA, UMR1260, Université Méditerranée Aix-Marseille 2, Faculté de Médecine, IPHM-IFR 125, Marseille, France.
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20
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Abstract
A primary function of the pancreas is to produce digestive enzymes that are delivered to the small intestine for the hydrolysis of complex nutrients. Much of our understanding of digestive enzymes comes from studies in animals. New technologies and the availability of the sequence of the human genome allow for a critical review of older reports and assumptions based on animal studies. This report updates our understanding of human pancreatic digestive enzymes with a focus on new insights into the biology of human proteases, lipases and amylases.
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Affiliation(s)
- David C Whitcomb
- Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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21
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Aloulou A, Rodriguez JA, Fernandez S, van Oosterhout D, Puccinelli D, Carrière F. Exploring the specific features of interfacial enzymology based on lipase studies. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:995-1013. [PMID: 16931141 DOI: 10.1016/j.bbalip.2006.06.009] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2006] [Revised: 06/17/2006] [Accepted: 06/27/2006] [Indexed: 11/28/2022]
Abstract
Many enzymes are active at interfaces in the living world (such as in the signaling processes at the surface of cell membranes, digestion of dietary lipids, starch and cellulose degradation, etc.), but fundamental enzymology remains largely focused on the interactions between enzymes and soluble substrates. The biochemical and kinetic characterization of lipolytic enzymes has opened up new paths of research in the field of interfacial enzymology. Lipases are water-soluble enzymes hydrolyzing insoluble triglyceride substrates, and studies on these enzymes have led to the development of specific interfacial kinetic models. Structure-function studies on lipases have thrown light on the interfacial recognition sites present in the molecular structure of these enzymes, the conformational changes occurring in the presence of lipids and amphiphiles, and the stability of the enzymes present at interfaces. The pH-dependent activity, substrate specificity and inhibition of these enzymes can all result from both "classical" interactions between a substrate or inhibitor and the active site, as well as from the adsorption of the enzymes at the surface of aggregated substrate particles such as oil drops, lipid bilayers or monomolecular lipid films. The adsorption step can provide an alternative target for improving substrate specificity and developing specific enzyme inhibitors. Several data obtained with gastric lipase, classical pancreatic lipase, pancreatic lipase-related protein 2 and phosphatidylserine-specific phospholipase A1 were chosen here to illustrate these specific features of interfacial enzymology.
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Affiliation(s)
- Ahmed Aloulou
- Laboratoire d'Enzymologie Interfaciale et de Physiologie de la Lipolyse, CNRS UPR 9025, 31 Chemin Joseph Aiguier, 13009 Marseille Cedex 20, France
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22
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Pietsch M, Gütschow M. Synthesis of tricyclic 1,3-oxazin-4-ones and kinetic analysis of cholesterol esterase and acetylcholinesterase inhibition. J Med Chem 2006; 48:8270-88. [PMID: 16366609 DOI: 10.1021/jm0508639] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of thieno[1,3]oxazin-4-ones and thieno[1,3]thiazin-4-ones were synthesized and investigated as inhibitors of the alpha/beta hydrolases cholesterol esterase (CEase) and acetylcholinesterase (AChE). The introduction of a cycloaliphatic five- or six-membered ring fused at the thiophene was favorable for CEase inhibition. Such compounds were analyzed as true alternate substrate inhibitors. 6,7-Dihydro-2-(dimethylamino)-4H,5H-cyclopenta[4,5]thieno[2,3-d][1,3]oxazin-4-one (33) exhibited a K(i) value of 630 nM and excelled in its low susceptibility to CEase-catalyzed degradation. Compound 33 and its analogues did not inhibit AChE. The introduction of a tetrahydropyrido ring with bulky hydrophobic substituents at the basic nitrogen provided inhibitors of AChE which were completely inactive toward CEase. 7-Benzyl-5,6,7,8-tetrahydro-2-(N-3,4-dimethoxybenzyl-N-methylamino)-4H-pyrido[4',3':4,5]thieno[2,3-d][1,3]oxazin-4-one (21) had the IC(50) value of 330 nM for AChE inhibition. A residual enzymatic activity at an infinite inhibitor concentration and thus a catalytically active ternary enzyme-substrate-inhibitor complex was concluded. To specify kinetic parameters of inhibition, a new method was derived to characterize selected thieno[1,3]oxazin-4-ones as hyperbolic mixed-type inhibitors of AChE.
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Affiliation(s)
- Markus Pietsch
- Pharmaceutical Institute, University of Bonn, Kreuzbergweg 26, D-53115 Bonn, Germany
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23
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Tao L, Harris AL. Biochemical requirements for inhibition of Connexin26-containing channels by natural and synthetic taurine analogs. J Biol Chem 2004; 279:38544-54. [PMID: 15234974 DOI: 10.1074/jbc.m405654200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Previous work has shown that protonated taurine and aminosulfonate pH buffers, including HEPES, can directly and reversibly inhibit connexin channels that contain connexin26 (Cx26) (Bevans, C. G., and Harris, A. L. (1999) J. Biol. Chem. 274, 3711-3719). The structural requirements for this inhibition were explored by studies of the effects of structural analogs of taurine on the activity of Cx26-containing reconstituted hemichannels from native tissue. Several analogs inhibited the channels, with a range of relative affinities and efficacies. Each active compound contains a protonated amine separated from an ionized sulfonate or sulfinate moiety by several methylene groups. The inhibition is eliminated if the sulfonate/sulfinate moiety or the amine is not present. Compounds that contain a protonated amine but lack a sulfonate/sulfinate moiety do not inhibit but do competitively block the effect of the active compounds. Compounds that lack the protonated amine do not significantly inhibit or antagonize inhibition. The results suggest involvement of the protonated amine in binding and of the ionized sulfur-containing moiety in effecting the inhibition. The maximal effect of the inhibitory compounds is enhanced when a carboxyl group is linked to the alpha-carbon. Inhibition but not binding is stereospecific, with l-isomers being inhibitory and the corresponding d-isomers being inactive but able to antagonize inhibition by the l-isomers. Whereas not all connexins are sensitive to aminosulfonates, the well defined structural requirements described here argue strongly for a highly specific regulatory interaction with some connexins. The finding that cytoplasmic aminosulfonates inhibit connexin channels whereas other cytoplasmic compounds antagonize the inhibition suggests that gap junction channels are regulated by a complex interplay of cytoplasmic ligands.
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Affiliation(s)
- Liang Tao
- Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA
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24
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Aubert-Jousset E, Sbarra V, Lombardo D. Site-directed Mutagenesis of the Distal Basic Cluster of Pancreatic Bile Salt-dependent Lipase. J Biol Chem 2004; 279:39697-704. [PMID: 15265857 DOI: 10.1074/jbc.m407646200] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have postulated the presence of two bile salt-binding sites regulating the activity of the pancreatic bile salt-dependent lipase. One of these sites, located in an N-terminal basic cluster, has been identified as the specific bile salt-binding site. Interaction of primary bile salts with this proximal site induces the formation of a micellar binding site from a pre-existing nonspecific or pre-micellar bile salt-binding site. Here we have investigated the functional significance of another basic cluster comprised of amino acid residues Arg(423), Lys(429), Arg(454), Arg(458), and Lys(462), distal from the catalytic site. For this purpose these residues were mutagenized in Ile or Ala residues. The mutagenized enzyme lost activity on both soluble and emulsified substrates in the presence of bile salts. However, in the absence of bile salts, the mutagenized enzyme displayed the same activity on soluble substrate as the wild-type recombinant enzyme. Consequently, the distal basic cluster may represent the nonspecific (or pre-micellar) bile salt-binding site susceptible to accommodate primary and secondary bile salts. According to the literature, tyrosine residue(s) should participate in this site. Therefore, two tyrosine residues, Tyr(427) and Tyr(453), associated with the distal basic cluster were also mutagenized. Each tyrosine substitution to serine did not inhibit the enzyme activity on soluble substrate, independently of the presence of primary or secondary bile salts. However, the enzyme activity on cholesteryl oleate solubilized in primary bile salt micelles was decreased by mutations substantiating that these residues are part of the nonspecific bile salt-binding site.
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Affiliation(s)
- Emeline Aubert-Jousset
- INSERM U-559, Unité de Recherche de Physiopathologie des Cellules Epitheliales, Faculté de Médecine, 27 Boulevard Jean Moulin, 13385 Marseille Cedex 5, France
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25
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Lookene A, Zhang L, Tougu V, Olivecrona G. 1,1'-bis(anilino)-4-,4'-bis(naphtalene)-8,8'-disulfonate acts as an inhibitor of lipoprotein lipase and competes for binding with apolipoprotein CII. J Biol Chem 2003; 278:37183-94. [PMID: 12855707 DOI: 10.1074/jbc.m303894200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lipoprotein lipase (LPL) is dependent on apolipoprotein CII (apoCII), a component of plasma lipoproteins, for function in vivo. The hydrophobic fluorescent probe 1,1'-bis(anilino)-4,4'-bis(naphthalene)-8,8'-disulfonate (bis-ANS) was found to be a potent inhibitor of LPL. ApoCII prevented the inhibition by bis-ANS, and was also able to restore the activity of inhibited LPL in a competitive manner, but only with triacylglycerols with acyl chains longer than three carbons. Studies of fluorescence and surface plasmon resonance indicated that LPL has an exposed hydrophobic site for binding of bis-ANS. The high affinity interaction was characterized by an equilibrium constant Kd of 0.10-0.26 microm and by a relatively high on rate constant kass = 2.0 x 10(4) m(-1) s(-1) and a slow off-rate with a dissociation rate constant kdiss = 1.2 x 10(-4) s(-1). The high affinity binding of bis-ANS did not influence interaction of LPL with heparin or with lipid/water interfaces and did not dissociate the active LPL dimer into monomers. Analysis of fragments of LPL after photoincorporation of bis-ANS indicated that the high affinity binding site was located in the middle part of the N-terminal folding domain. We propose that bis-ANS binds to an exposed hydrophobic area that is located close to the active site. This area may be the binding site for individual substrate molecules and also for apoCII.
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Affiliation(s)
- Aivar Lookene
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden SE-901 87
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26
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Hui DY, Howles PN. Carboxyl ester lipase: structure-function relationship and physiological role in lipoprotein metabolism and atherosclerosis. J Lipid Res 2002; 43:2017-30. [PMID: 12454261 DOI: 10.1194/jlr.r200013-jlr200] [Citation(s) in RCA: 156] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Carboxyl ester lipase (CEL), previously named cholesterol esterase or bile salt-stimulated (or dependent) lipase, is a lipolytic enzyme capable of hydrolyzing cholesteryl esters, tri-, di-, and mono-acylglycerols, phospholipids, lysophospholipids, and ceramide. The active site catalytic triad of serine-histidine-aspartate is centrally located within the enzyme structure and is partially covered by a surface loop. The carboxyl terminus of the protein regulates enzymatic activity by forming hydrogen bonds with the surface loop to partially shield the active site. Bile salt binding to the loop domain frees the active site for accessibility by water-insoluble substrates. CEL is synthesized primarily in the pancreas and lactating mammary gland, but the enzyme is also expressed in liver, macrophages, and in the vessel wall. In the gastrointestinal tract, CEL serves as a compensatory protein to other lipolytic enzymes for complete digestion and absorption of lipid nutrients. Importantly, CEL also participates in chylomicron assembly and secretion, in a mechanism mediated through its ceramide hydrolytic activity. Cell culture studies suggest a role for CEL in lipoprotein metabolism and oxidized LDL-induced atherosclerosis. Thus, this enzyme, which has a wide substrate reactivity and diffuse anatomic distribution, may have multiple functions in lipid and lipoprotein metabolism, and atherosclerosis.
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Affiliation(s)
- David Y Hui
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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27
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Fält H, Hernell O, Bläckberg L. Does bile salt-stimulated lipase affect cholesterol uptake when bound to rat intestinal mucosa in vitro? Pediatr Res 2002; 52:509-15. [PMID: 12357044 DOI: 10.1203/00006450-200210000-00009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Bile salt-stimulated lipase (BSSL), or carboxyl ester lipase, is a constituent of exocrine pancreatic secretion and, in some species, including humans, also of milk. BSSL has been suggested to have a direct effect on intestinal uptake of dietary cholesterol besides being the key enzyme in the hydrolysis of fat-soluble vitamins and cholesterol esters. Furthermore, an intestinal heparin-containing receptor for the enzyme has been implicated. If BSSL promotes dietary cholesterol utilization, this might be of particular importance in the neonatal period, which is characterized by a high need of cholesterol for membrane synthesis. We have studied binding of BSSL to intestinal membranes in vitro and if such binding affects the uptake of cholesterol. BSSL bound avidly to rat intestinal microvesicle membranes and the binding was inhibited by addition of free heparin or heparin fragments. In this model system, we could not demonstrate any effect of BSSL on cellular uptake of free cholesterol. However, if esterified rather than free cholesterol was present in the incubation, hydrolysis by BSSL was the rate-limiting step in cellular cholesterol uptake. We therefore conclude that BSSL is important for utilization of dietary cholesterol only by hydrolyzing cholesterol esters and not by acting as a transport protein.
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Affiliation(s)
- Helen Fält
- Department of Medical Biosciences, Physiological Chemistry, Umeå University, Umeå, Sweden.
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28
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Aubert E, Sbarra V, Le Petit-Thévenin J, Valette A, Lombardo D. Site-directed mutagenesis of the basic N-terminal cluster of pancreatic bile salt-dependent lipase. Functional significance. J Biol Chem 2002; 277:34987-96. [PMID: 12110666 DOI: 10.1074/jbc.m202893200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previous studies have postulated the presence of a heparin-binding site on the bile salt-dependent lipase (BSDL), whereas two bile salt-binding sites regulate the enzyme activity. One of these sites may overlap with the tentative heparin-binding site at the level of an N-terminal basic cluster consisting of positive residues Lys(32), Lys(56), Lys(61), Lys(62), and Arg(63). The present study uses specific site-directed mutagenesis to determine the functional significance of this basic cluster. Mutations in this sequence resulted in recombinant enzymes that were able to bind to immobilized and to cell-associated heparin before moving throughout intestinal cells. Recombinant BSDL was fully active on soluble substrate, but mutants were less active on micellar cholesteryl oleate in comparison with the wild-type enzyme. Activation studies by primary (sodium taurocholate) and by secondary (sodium taurodeoxycholate) bile salts revealed that the activation of BSDL by sodium taurocholate at concentrations below the critical micellar concentration, and not that evoked by micellar bile salts, was affected by substitutions, suggesting that this N-terminal basic cluster likely represents the specific bile salt-binding site of BSDL. Substitutions also affected the activation of the enzyme promoted by anionic phospholipids, extending the function of this site to that of a cationic regulatory site susceptible to accommodate anionic ligands.
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Affiliation(s)
- Emeline Aubert
- INSERM U-559, Unité de Recherche de Physiopathologie des Cellules Epitheliales, Faculté de Médecine, 27 blv Jean MOULIN, 13385 Marseille cedex 05, France
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