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Boutin JA, Tartar AL, van Dorsselaer A, Vaudry H. General lack of structural characterization of chemically synthesized long peptides. Protein Sci 2019; 28:857-867. [PMID: 30851143 PMCID: PMC6459998 DOI: 10.1002/pro.3601] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 03/07/2019] [Accepted: 03/07/2019] [Indexed: 01/01/2023]
Abstract
Many peptide chemistry scientists have been reporting extremely interesting work on the basis of chemical peptides for which the only characterization was their purity, mass, and biological activity. It seems slightly overenthusiastic, as many of these structures should be thoroughly characterized first to demonstrate the uniqueness of the structure, as opposed to the uniqueness of the sequence. Among the peptides of identical sequences in the final chemical preparation, what amount of well-folded peptide supports the measured activity? The activity of a peptide preparation cannot prove the purity of the desired peptide. Therefore, greater care should be taken in characterizing peptides, particularly those coming from chemical synthesis. At a time when the pharmaceutical industry is changing its paradigm by moving substantially from small molecules to biologics to better serve patients' needs, it is important to understand the limitations of the descriptions of these products and to start to apply the same "good laboratory practices" to our peptide research. Here, we attempt to delineate how synthetic peptides are described and characterized and what will be needed to describe them in regards to how they are well-folded and homogeneous in their tertiary structure. Older studies were done when the tools were not yet discovered, but more recent publications are still lacking proper descriptions of these peptides. Modern tools of analysis are capable of segregating folded and unfolded peptides, even if the preparation is biologically active.
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Affiliation(s)
- Jean A. Boutin
- Institut de Recherches Internationales Servier50 rue Carnot, 92284, Suresnes‐CedexFrance
| | - André L. Tartar
- Faculté de Pharmacie 3rue du Professeur Laguesse, BP83 ‐ 59006, Lille‐CedexFrance
| | - Alain van Dorsselaer
- Laboratoire de Spectrométrie de Masse Bio‐Organique, Département des Sciences AnalytiquesInstitut Pluridisciplinaire Hubert CurienUMR 7178 (CNRS‐UdS), ECPM, 25 rue Becquerel, F67087, Strasbourg‐Cedex 2France
| | - Hubert Vaudry
- Plate‐Forme de Recherche en Imagerie Cellulaire de Normandie (PRIMACEN)Institut de Recherche et d'Innovation Biomédicales (IRIB), Université de Rouen76821, Mont‐Saint‐Aignan CedexFrance
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2
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de Veer SJ, Ukolova SS, Munro CA, Swedberg JE, Buckle AM, Harris JM. Mechanism-based selection of a potent kallikrein-related peptidase 7 inhibitor from a versatile library based on the sunflower trypsin inhibitor SFTI-1. Biopolymers 2016; 100:510-8. [PMID: 24078181 DOI: 10.1002/bip.22231] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 03/01/2013] [Accepted: 03/02/2013] [Indexed: 02/06/2023]
Abstract
Potent and specific enzyme inhibition is a key goal in the development of therapeutic inhibitors targeting proteolytic activity. The backbone-cyclized peptide, Sunflower Trypsin Inhibitor (SFTI-1) affords a scaffold that can be engineered to achieve both these aims. SFTI-1's mechanism of inhibition is unusual in that it shows fast-on/slow-off kinetics driven by cleavage and religation of a scissile bond. This phenomenon was used to select a nanomolar inhibitor of kallikrein-related peptidase 7 (KLK7) from a versatile library of SFTI variants with diversity tailored to exploit distinctive surfaces present in the active site of serine proteases. Inhibitor selection was achieved through the use of size exclusion chromatography to separate protease/inhibitor complexes from unbound inhibitors followed by inhibitor identification according to molecular mass ascertained by mass spectrometry. This approach identified a single dominant inhibitor species with molecular weight of 1562.4 Da, which is consistent with the SFTI variant SFTI-WCTF. Once synthesized individually this inhibitor showed an IC50 of 173.9 ± 7.6 nM against chromogenic substrates and could block protein proteolysis. Molecular modeling analysis suggested that selection of SFTI-WCTF was driven by specific aromatic interactions and stabilized by an enhanced internal hydrogen bonding network. This approach provides a robust and rapid route to inhibitor selection and design.
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Affiliation(s)
- Simon J de Veer
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, 4059, Australia
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3
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Giulianotti MA, Debevec G, Santos RG, Maida LE, Chen W, Ou L, Yu Y, Dooley CT, Houghten RA. A novel method for the determination of isokinetic ratios and its application in the synthesis of two new positional scanning libraries. ACS COMBINATORIAL SCIENCE 2012; 14:503-12. [PMID: 22913403 DOI: 10.1021/co300060s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A novel method for the direct evaluation of the equimolarity of the compounds contained in a mixture is presented. We applied the method toward calculating isokinetic ratios for the reaction between the amine termini of a resin bound peptide fragment and a sulfonyl chloride to produce equal molar mixtures of sulfonamides. The results of this study and the application of the method to the synthesis of two new positional scanning synthetic combinatorial libraries (PS-SCL) are discussed.
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Affiliation(s)
- Marc A. Giulianotti
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
| | - Ginamarie Debevec
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
| | - Radleigh G. Santos
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
| | - Laura E. Maida
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
| | - Wenteng Chen
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
- College of Pharmaceutical Science, Zhejiang University, Hangzhou, P.R. China 310058
| | - Lili Ou
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
- College of Pharmaceutical Science, Zhejiang University, Hangzhou, P.R. China 310058
| | - Yongping Yu
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
- College of Pharmaceutical Science, Zhejiang University, Hangzhou, P.R. China 310058
| | - Colette T. Dooley
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
| | - Richard A. Houghten
- Torrey Pines Institute for Molecular Studies, 11350 SW Village Parkway, Port
St. Lucie, Florida 34987, United States
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4
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Swedberg JE, Harris JM. Natural and engineered plasmin inhibitors: applications and design strategies. Chembiochem 2012; 13:336-48. [PMID: 22238174 DOI: 10.1002/cbic.201100673] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Indexed: 12/17/2022]
Abstract
The serine protease plasmin is ubiquitously expressed throughout the human body in the form of the zymogen plasminogen. Conversion to active plasmin occurs through enzymatic cleavage by plasminogen activators. The plasminogen activator/plasmin system has a well-established function in the removal of intravascular fibrin deposition through fibrinolysis and the inhibition of plasmin activity; this has found widespread clinical use in reducing perioperative bleeding. Increasing evidence also suggests diverse, although currently less defined, roles for plasmin in a number of physiological and pathological processes relating to extracellular matrix degradation, cell migration and tissue remodelling. In particular, dysregulation of plasmin has been linked to cancer invasion/metastasis and various chronic inflammatory conditions; this has prompted efforts to develop inhibitors of this protease. Although a number of plasmin inhibitors exist, they commonly suffer from poor potency and/or specificity of inhibition that either results in reduced efficacy or prevents clinical use. Consequently, there is a need for further development of high-affinity plasmin inhibitors that maintain selectivity over other serine proteases. This review summarises clearly defined and potential applications for plasmin inhibition. The properties of naturally occurring and engineered plasmin inhibitors are discussed in the context of current knowledge regarding plasmin structure, specificity and function. This includes design strategies to obtain the potency and specificity of inhibition in addition to controlled temporal and spatial distribution tailored for the intended use.
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Affiliation(s)
- Joakim E Swedberg
- Institute for Molecular Bioscience, The University of Queensland, Brisbane QLD 4072 (Australia)
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5
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Swedberg JE, Harris JM. Plasmin Substrate Binding Site Cooperativity Guides the Design of Potent Peptide Aldehyde Inhibitors. Biochemistry 2011; 50:8454-62. [DOI: 10.1021/bi201203y] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Joakim E. Swedberg
- Institute of Health and
Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland
4059, Australia
| | - Jonathan M. Harris
- Institute of Health and
Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland
4059, Australia
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6
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Bicker KL, Obianyo O, Rust HL, Thompson PR. A combinatorial approach to characterize the substrate specificity of protein arginine methyltransferase 1. MOLECULAR BIOSYSTEMS 2010; 7:48-51. [PMID: 20607165 DOI: 10.1039/c0mb00015a] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The dysregulation of protein arginine methyltransferases (PRMTs) is implicated in a wide variety of disease states. Here we report the design, synthesis, and screening of a combinatorial peptide library used to characterize the substrate specificity of PRMT1. The information gained from this approach was used to develop a PRMT1 inhibitor with enhanced selectivity.
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Affiliation(s)
- Kevin L Bicker
- Department of Chemistry and Biochemistry, University of South Carolina, 631 Sumter St, Columbia, South Carolina, USA
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7
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Vetter SW, Zhang ZY. Combinatorial Chemistry and Peptide Library Methods to Characterize Protein Phosphatases. Methods Enzymol 2003; 366:260-82. [PMID: 14674254 DOI: 10.1016/s0076-6879(03)66020-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Stefan W Vetter
- Department of Molecular Biology, Scripps Research Institute, 10550 North Torrey Pines Blvd, La Jolla, California 92037, USA
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8
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Henlin JM, Boutin JA, Kucharczyk N, Desmet-Beaufort C, Loynel A, Bertrand M, Genton A, Tucker GC, Atassi G, Fauchére JL. From peptide libraries to optimized nonpeptide ligands in the search for S-farnesyltransferase inhibitors. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 2001; 57:85-96. [PMID: 11168892 DOI: 10.1034/j.1399-3011.2001.00787.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A complete 331,776-member library of tetrapeptides made of 24 amino acid building blocks was synthesized robotically on solid phase and subjected to a deconvolution based on the inhibitory potency of the sublibraries in a HPLC assay of the S-farnesyltransferase activity in vitro. One of the non-natural peptide and noncysteine-containing leads Nip-Trp-Phe-His (Nip=p-nitrophenyl-L-alanine) was optimized chemically to give a proteolytically stable pseudopeptide with a 200-fold potency compared with the original lead. The final compound was converted to the C-terminal ethyl ester: p-F-C6H4-CO(CH2)2-CO-Bta-D-Phepsi[CH2NH]His-OEt (Bta = benzothienyl-L-alanine) and shown to behave as a prodrug which was hydrolyzed back to the C-terminal acid following cell penetration. The method confirmed that several structurally original leads can be discovered in large libraries when deconvolution relies upon a highly specific assay and that these leads can be optimized by chemical modification to impart the final compound the desired pharmacological and pharmacokinetic properties.
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Affiliation(s)
- J M Henlin
- Institut de Recherches Servier, Suresnes, France
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9
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Kassel DB. Combinatonial chemistry and mass spectrometry in the 21st century drug discovery laboratory. Chem Rev 2001; 101:255-67. [PMID: 11712247 DOI: 10.1021/cr990085q] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- D B Kassel
- DuPont Pharmaceuticals Research Laboratories, 4570 Executive Drive, Suite 400, San Diego, California 92121, USA.
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10
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Ferry G, Loynel A, Kucharczyk N, Bertin S, Rodriguez M, Delagrange P, Galizzi JP, Jacoby E, Volland JP, Lesieur D, Renard P, Canet E, Fauchère JL, Boutin JA. Substrate specificity and inhibition studies of human serotonin N-acetyltransferase. J Biol Chem 2000; 275:8794-805. [PMID: 10722724 DOI: 10.1074/jbc.275.12.8794] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Arylalkylamine N-acetyltransferase (AANAT) catalyzes the reaction of serotonin with acetyl-CoA to form N-acetylserotonin and plays a major role in the regulation of the melatonin circadian rhythm in vertebrates. In the present study, the human cloned enzyme has been expressed in bacteria, purified, cleaved, and characterized. The specificity of the human enzyme toward substrates (natural as well as synthetic arylethylamines) and cosubstrates (essentially acyl homologs of acetyl-CoA) has been investigated. Peptide combinatorial libraries of tri-, tetra-, and pentapeptides with various amino acid compositions were also screened as potential sources of inhibitors. We report the findings of several peptides with low micromolar inhibitory potency. For activity measurement as well as for specificity studies, an original and rapid method of analysis was developed. The assay was based on the separation and detection of N-[(3)H]acetylarylethylamine formed from various arylethylamines and tritiated acetyl-CoA, by means of high performance liquid chromatography with radiochemical detection. The assay proved to be robust and flexible, could accommodate the use of numerous synthetic substrates, and was successfully used throughout this study. We also screened a large number of pharmacological bioamines among which only one, tranylcypromine, behaved as a substrate. The synthesis and survey of simple arylethylamines also showed that AANAT has a large recognition pattern, including compounds as different as phenyl-, naphthyl-, benzothienyl-, or benzofuranyl-ethylamine derivatives. An extensive enzymatic study allowed us to pinpoint the amino acid residue of the pentapeptide inhibitor, S 34461, which interacts with the cosubstrate-binding site area, in agreement with an in silico study based on the available coordinates of the hAANAT crystal.
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Affiliation(s)
- G Ferry
- Division de Pharmacologie Moléculaire et Cellulaire, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy sur Seine, France
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11
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Vetter SW, Keng YF, Lawrence DS, Zhang ZY. Assessment of protein-tyrosine phosphatase 1B substrate specificity using "inverse alanine scanning". J Biol Chem 2000; 275:2265-8. [PMID: 10644673 DOI: 10.1074/jbc.275.4.2265] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An "inverse alanine scanning" peptide library approach has been developed to assess the substrate specificity of protein-tyrosine phosphatases (PTPases). In this method each Ala moiety in the parent peptide, Ac-AAAApYAAAA-NH(2), is separately and sequentially replaced by the 19 non-Ala amino acids to generate a library of 153 well defined peptides. The relatively small number of peptides allows the acquisition of explicit kinetic data for all library members, thereby furnishing information about the contribution of individual amino acids with respect to substrate properties. The approach was applied to protein-tyrosine phosphatase 1B (PTP1B) as a first example, and the highly potent peptide substrate Ac-ELEFpYMDYE-NH(2) (k(cat)/K(m) 2.2 +/- 0.05 x 10(7) M(-1) s(-1)) has been identified. More importantly, several heretofore unknown features of the substrate specificity of PTP1B were revealed. This includes the ability of PTP1B to accommodate acidic, aromatic, and hydrophobic residues at the -1 position, a strong nonpreference for Lys and Arg residues in any position, and the first evidence that residues well beyond the +1 position contribute to substrate efficacy.
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Affiliation(s)
- S W Vetter
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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12
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Boutin JA, Lahaye C, Pegurier C, Nicolas JP, Fauchere JL, Langlois M, Renard P, Delagrange P, Canet E. Screening of ligand binding on melatonin receptor using non-peptide combinatorial libraries. J Recept Signal Transduct Res 2000; 20:105-18. [PMID: 10711500 DOI: 10.3109/10799890009150040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The screening of combinatorial libraries requires a deconvolution procedure to obtain, in fine, the most active compound of the starting library. The standard screening assays used in regular molecular pharmacology, have been poorly assessed when transposed to combinatorial chemistry-related experiments, particularly those involving large numbers of chemicals in a single assay. One key issue is the effect of the inactive analogs on the identification of the active ligand in mixtures. We chose melatonin receptors to measure the apparent affinity of a single ligand when tested alone or in mixtures of non-peptide low molecular weight compounds. Using ligands with IC50 from the micro- to the picomolar range, mixed with increasingly complex mixtures of 5 to 20 or 25 inactive compounds, we analyzed the displacements from the mt1 and MT2 melatonin receptor subtypes of the radioligand 2-iodomelatonin (KD= 25 pmol/l and 200 pmol/l, respectively) . The behavior of equimolar mixtures in displacement curves led to the conclusion that the observed binding affinity reflects the dilution effect of mixing the active component with inactive compounds but does not reveal noticeable interactions which would interfere with the binding process. From the practical point of view, the concentrations of the active species in the binding assay should be large enough to displace significantly the radioligand, a requirement which may be limited by the solubility of the ligand mixtures. In contrast, previous observations with peptide libraries report that the dilution effect is often compensated by additive or synergic action of structurally related analogs, thus making possible the deconvolution of very large (typically up to 10(7) compounds) peptide libraries.
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Affiliation(s)
- J A Boutin
- Division de Pharmacologie Moléculaire et Cellulaire, Institut de Recherches SERVIER, Croissy-sur-Seine, France
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13
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Boutin JA, Lambert PH, Bertin S, Volland JP, Fauchère JL. Physico-chemical and biological analysis of true combinatorial libraries. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1999; 725:17-37. [PMID: 10226875 DOI: 10.1016/s0378-4347(98)00569-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Combinatorial libraries offer new sources of compounds for the research of pharmacological agents such as receptor ligands, enzyme inhibitors or substrates and antibody-binding epitopes. The present review stresses the main roles played by both physico-chemical analysis, particularly when complex mixture of compounds are synthesized as libraries, and biological analysis from which active compounds are identified. After a brief discussion of semantic problems related to the designation of the product mixtures, the physico-chemical analysis of mixtures is reviewed with special emphasis on mass spectrometric techniques. These methods are able both to give a representative view of a library composition and to identify single critical compounds in large libraries. Then the biological screening of such combinatorial libraries is critically discussed with respect to the power and limitations of the methods used for the identification of the active components. Special attention is given to the complex process of library deconvolution. It is pointed out that while combinatorial techniques have evolved towards sophisticated high-tech methods, simple and robust biochemical tests should be used to deconvolute. From a large panel of published examples, a set of trends are identified which should help investigators to choose the most appropriate assay for the discovery of new entities.
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Affiliation(s)
- J A Boutin
- Department of Molecular and Cellular Pharmacology, Institut de Recherches SERVIER, Croissy-sur-Seine, France
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14
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Süssmuth RD, Jung G. Impact of mass spectrometry on combinatorial chemistry. JOURNAL OF CHROMATOGRAPHY. B, BIOMEDICAL SCIENCES AND APPLICATIONS 1999; 725:49-65. [PMID: 10226877 DOI: 10.1016/s0378-4347(98)00513-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the past few years, the emergence of combinatorial chemistry has drawn increasing attention and a great deal of analytical research has been centered around this new methodology. These new methods capable of producing vast numbers of samples, which are in many cases highly complex, demand fast and reliable analytical techniques able to provide high quality information concerning sample compositions. Mass spectrometry (MS) is the method of choice to face these analytical challenges. In particular, the introduction of electrospray ionization (ESI and matrix assisted laser desorption/ionization (MALDI) have been the driving forces for many of the recent innovations, not only within the fields of the biosciences, but also in combinatorial chemistry. These ionization techniques are extremely versatile for the characterization of both single compound collections and compound mixture collections. The high-throughput capabilities, as well as many possible couplings with separation techniques (HPLC, CE) have been thus facilitated. However, mass spectrometry is not only limited to use as an instrument for synthesis control, but also plays an increasing role in the identification of active compounds from complex libraries. Recently, new initiatives for library analysis and screening have arisen from the application of the latest developments in mass spectrometry, Fourier transform ion cyclotron resonance (FTICR).
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Affiliation(s)
- R D Süssmuth
- University of Tübingen, Institute of Organic Chemistry, Germany.
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15
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Boutin JA, Marande W, Petit L, Loynel A, Desmet C, Canet E, Fauchère JL. Investigation of S-farnesyl transferase substrate specificity with combinatorial tetrapeptide libraries. Cell Signal 1999; 11:59-69. [PMID: 10206346 DOI: 10.1016/s0898-6568(98)00032-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using biased tetrapeptide libraries made up of proteinogenic amino acids of the general formula Cys-O2-X3-X4, we searched for new substrates of partly purified rat brain S-farnesyl transferase (FTase). To achieve this task, an assay was developed in which the consumption of the co-substrate (farnesyl pyrophosphate) was measured. After three steps of deconvolution including each synthesis and enzymatic assay, the most efficient substrates found under these particular conditions were Cys-Lys-Gln-Gln (peptide I) and Cys-Lys-Gln-Met (peptide II). As a control, we used another tetrapeptide library (Cys-Val-O3-X4) in which the valine position was arbitrarily fixed, corresponding to Cys-Val-Ile-Met in the CAAX box of K-RasB, although this sublibrary was only marginally active compared with Cys-Lys-X3-X4 in the first round of deconvolution. The best substrate sublibrary was Cys-Val-Thr-X4, threonine being more favourable than the aliphatic amino acids (Val, Ile, Leu, Ala) in this position. Deconvolution finally led to Cys-Val-Thr-Gln, -Met, -Thr and -Ser as the most efficient substrates of FTase. Those tetrapeptides were not substrates of a partly purified geranylgeranyl transferase 1 (GGTase1). We also investigated the influence of the -1 position (at the N-terminus of cysteine) on the specificity of the enzyme, by using a series of pentapeptides constructed on the basis of the best tetrapeptide core (peptide 1). Among this family of analogues, only His-Cys-Lys-Gln-Gln did not behave as a substrate, whereas all the other pentapeptides were measurable substrates, with Gly-, Asn- and Thr-Cys-Lys-Gln-Gln displaying kinetic constants similar to that of Cys-Lys-Gln-Gln. The present work provides strong evidence that the best tetrapeptide substrates of FTase do not necessarily belong to the classical CAAX box, in which A's are lipophilic residues, but rather contain hydrophilic amino acids in the middle of their sequences. Among them, peptides I and II are potent FTase in vitro substrates that are not recognised by GGTase1 and might be new starting points for the design of FTase inhibitors.
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Affiliation(s)
- J A Boutin
- Department of Peptides and Combinatorial Chemistry, Institut de Recherches SERVIER, Suresnes, France.
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