1
|
Schäker‐Hübner L, Haschemi R, Büch T, Kraft FB, Brumme B, Schöler A, Jenke R, Meiler J, Aigner A, Bendas G, Hansen FK. Balancing Histone Deacetylase (HDAC) Inhibition and Drug-likeness: Biological and Physicochemical Evaluation of Class I Selective HDAC Inhibitors. ChemMedChem 2022; 17:e202100755. [PMID: 35073610 PMCID: PMC9303312 DOI: 10.1002/cmdc.202100755] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Indexed: 11/08/2022]
Abstract
Herein we report the structure-activity and structure-physicochemical property relationships of a series of class I selective ortho-aminoanilides targeting the "foot-pocket" in HDAC1&2. To balance the structural benefits and the physicochemical disadvantages of these substances, we started with a set of HDACi related to tacedinaline (CI-994) and evaluated their solubility, lipophilicity (log D7.4 ) and inhibition of selected HDAC isoforms. Subsequently, we selected the most promising "capless" HDACi and transferred its ZBG to our previously published scaffold featuring a peptoid-based cap group. The resulting hit compound 10 c (LSH-A54) showed favorable physicochemical properties and is a potent, selective HDAC1/2 inhibitor. The following evaluation of its slow binding properties revealed that LSH-A54 binds tightly to HDAC1 in an induced-fit mechanism. The potent HDAC1/2 inhibitory properties were reflected by attenuated cell migration in a modified wound healing assay and reduced cell viability in a clonogenic survival assay in selected breast cancer cell lines.
Collapse
Affiliation(s)
- Linda Schäker‐Hübner
- Institut für WirkstoffentwicklungMedizinische FakultätUniversität LeipzigBrüderstraße 3404103LeipzigGermany
- Abteilung für Pharmazeutische und Zellbiologische ChemiePharmazeutisches InstitutUniversität BonnAn der Immenburg 453121BonnGermany
| | - Reza Haschemi
- Abteilung für Pharmazeutische und Zellbiologische ChemiePharmazeutisches InstitutUniversität BonnAn der Immenburg 453121BonnGermany
| | - Thomas Büch
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Klinische PharmakologieMedizinische FakultätUniversität LeipzigHärtelstraße 16–1804107LeipzigGermany
| | - Fabian B. Kraft
- Abteilung für Pharmazeutische und Zellbiologische ChemiePharmazeutisches InstitutUniversität BonnAn der Immenburg 453121BonnGermany
| | - Birke Brumme
- Institut für WirkstoffentwicklungMedizinische FakultätUniversität LeipzigBrüderstraße 3404103LeipzigGermany
| | - Andrea Schöler
- Institut für WirkstoffentwicklungMedizinische FakultätUniversität LeipzigBrüderstraße 3404103LeipzigGermany
| | - Robert Jenke
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Klinische PharmakologieMedizinische FakultätUniversität LeipzigHärtelstraße 16–1804107LeipzigGermany
- University Cancer Center Leipzig (UCCL)Universitätsklinikum LeipzigLiebigstraße 22, Haus 704103LeipzigGermany
| | - Jens Meiler
- Institut für WirkstoffentwicklungMedizinische FakultätUniversität LeipzigBrüderstraße 3404103LeipzigGermany
| | - Achim Aigner
- Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Klinische PharmakologieMedizinische FakultätUniversität LeipzigHärtelstraße 16–1804107LeipzigGermany
| | - Gerd Bendas
- Abteilung für Pharmazeutische und Zellbiologische ChemiePharmazeutisches InstitutUniversität BonnAn der Immenburg 453121BonnGermany
| | - Finn K. Hansen
- Abteilung für Pharmazeutische und Zellbiologische ChemiePharmazeutisches InstitutUniversität BonnAn der Immenburg 453121BonnGermany
| |
Collapse
|
2
|
McGregor NGS, Artola M, Nin-Hill A, Linzel D, Haon M, Reijngoud J, Ram A, Rosso MN, van der Marel GA, Codée JDC, van Wezel GP, Berrin JG, Rovira C, Overkleeft HS, Davies GJ. Rational Design of Mechanism-Based Inhibitors and Activity-Based Probes for the Identification of Retaining α-l-Arabinofuranosidases. J Am Chem Soc 2020; 142:4648-4662. [PMID: 32053363 PMCID: PMC7068720 DOI: 10.1021/jacs.9b11351] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
![]()
Identifying
and characterizing the enzymes responsible for an observed
activity within a complex eukaryotic catabolic system remains one
of the most significant challenges in the study of biomass-degrading
systems. The debranching of both complex hemicellulosic and pectinaceous
polysaccharides requires the production of α-l-arabinofuranosidases
among a wide variety of coexpressed carbohydrate-active enzymes. To
selectively detect and identify α-l-arabinofuranosidases
produced by fungi grown on complex biomass, potential covalent inhibitors
and probes which mimic α-l-arabinofuranosides were
sought. The conformational free energy landscapes of free α-l-arabinofuranose and several rationally designed covalent α-l-arabinofuranosidase inhibitors were analyzed. A synthetic
route to these inhibitors was subsequently developed based on a key
Wittig–Still rearrangement. Through a combination of kinetic
measurements, intact mass spectrometry, and structural experiments,
the designed inhibitors were shown to efficiently label the catalytic
nucleophiles of retaining GH51 and GH54 α-l-arabinofuranosidases.
Activity-based probes elaborated from an inhibitor with an aziridine
warhead were applied to the identification and characterization of
α-l-arabinofuranosidases within the secretome of A. niger grown on arabinan. This method was extended to
the detection and identification of α-l-arabinofuranosidases
produced by eight biomass-degrading basidiomycete fungi grown on complex
biomass. The broad applicability of the cyclophellitol-derived activity-based
probes and inhibitors presented here make them a valuable new tool
in the characterization of complex eukaryotic carbohydrate-degrading
systems and in the high-throughput discovery of α-l-arabinofuranosidases.
Collapse
Affiliation(s)
- Nicholas G S McGregor
- York Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5DD, U.K
| | - Marta Artola
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Alba Nin-Hill
- Departament de Quı́mica Inorgànica i Orgànica (Secció de Quı́mica Orgànica) & Institut de Quı́mica Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
| | - Daniël Linzel
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Mireille Haon
- INRA, Aix Marseille University, Biodiversité et Biotechnologie Fongiques (BBF), UMR1163, F-13009 Marseille, France
| | - Jos Reijngoud
- Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Arthur Ram
- Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Marie-Noëlle Rosso
- INRA, Aix Marseille University, Biodiversité et Biotechnologie Fongiques (BBF), UMR1163, F-13009 Marseille, France
| | - Gijsbert A van der Marel
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Jeroen D C Codée
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Gilles P van Wezel
- Molecular Microbiology and Biotechnology, Institute of Biology Leiden, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands
| | - Jean-Guy Berrin
- INRA, Aix Marseille University, Biodiversité et Biotechnologie Fongiques (BBF), UMR1163, F-13009 Marseille, France
| | - Carme Rovira
- Departament de Quı́mica Inorgànica i Orgànica (Secció de Quı́mica Orgànica) & Institut de Quı́mica Teòrica i Computacional (IQTCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), 08020 Barcelona, Spain
| | - Herman S Overkleeft
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Gideon J Davies
- York Structural Biology Laboratory, Department of Chemistry, The University of York, Heslington, York YO10 5DD, U.K
| |
Collapse
|
3
|
Yadav J, Paragas E, Korzekwa K, Nagar S. Time-dependent enzyme inactivation: Numerical analyses of in vitro data and prediction of drug-drug interactions. Pharmacol Ther 2020; 206:107449. [PMID: 31836452 PMCID: PMC6995442 DOI: 10.1016/j.pharmthera.2019.107449] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Cytochrome P450 (CYP) enzyme kinetics often do not conform to Michaelis-Menten assumptions, and time-dependent inactivation (TDI) of CYPs displays complexities such as multiple substrate binding, partial inactivation, quasi-irreversible inactivation, and sequential metabolism. Additionally, in vitro experimental issues such as lipid partitioning, enzyme concentrations, and inactivator depletion can further complicate the parameterization of in vitro TDI. The traditional replot method used to analyze in vitro TDI datasets is unable to handle complexities in CYP kinetics, and numerical approaches using ordinary differential equations of the kinetic schemes offer several advantages. Improvement in the parameterization of CYP in vitro kinetics has the potential to improve prediction of clinical drug-drug interactions (DDIs). This manuscript discusses various complexities in TDI kinetics of CYPs, and numerical approaches to model these complexities. The extrapolation of CYP in vitro TDI parameters to predict in vivo DDIs with static and dynamic modeling is discussed, along with a discussion on current gaps in knowledge and future directions to improve the prediction of DDI with in vitro data for CYP catalyzed drug metabolism.
Collapse
Affiliation(s)
- Jaydeep Yadav
- Amgen Inc., 360 Binney Street, Cambridge, MA 02142, United States; Department of Pharmaceutical Sciences, Temple University, Philadelphia, PA 19140, United States
| | - Erickson Paragas
- Department of Pharmaceutical Sciences, Temple University, Philadelphia, PA 19140, United States
| | - Ken Korzekwa
- Department of Pharmaceutical Sciences, Temple University, Philadelphia, PA 19140, United States
| | - Swati Nagar
- Department of Pharmaceutical Sciences, Temple University, Philadelphia, PA 19140, United States.
| |
Collapse
|
4
|
In Vitro Evaluation of Serine Hydrolase Inhibitors. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2018. [DOI: 10.1007/7653_2018_11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
|
5
|
Kang TW, Jeon SJ, Kim HI, Park JH, Yim D, Lee HR, Ju JM, Kim MJ, Kim JH. Optical Detection of Enzymatic Activity and Inhibitors on Non-Covalently Functionalized Fluorescent Graphene Oxide. ACS NANO 2016; 10:5346-5353. [PMID: 27136042 DOI: 10.1021/acsnano.6b01495] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
It has been of great interest to measure the activity of acetylcholinesterase (AChE) and its inhibitor, as AChE is known to accelerate the aggregation of the amyloid beta peptides that underlie Alzheimer's disease. Herein, we report the development of graphene oxide (GO) fluorescence-based biosensors for the detection of AChE activity and AChE inhibitors. To this end, GO was non-covalently functionalized with phenoxy-modified dextran (PhO-dex-GO) through hydrophobic interaction; the resulting GO showed excellent colloidal stability and intense fluorescence in various aqueous solutions as compared to pristine GO and the GO covalently functionalized with dextran. The fluorescence of PhO-dex-GO remarkably increased as AChE catalyzed the hydrolysis of acetylthiocholine (ATCh) to give thiocholine and acetic acid. It was found that the turn-on fluorescence response of PhO-dex-GO to AChE activity was induced by protonation of carboxyl groups on it from the product of the enzymatic hydrolysis reaction, acetic acid. On the basis of its turn-on fluorescence response, PhO-dex-GO was able to report kinetic and thermodynamic parameters involving a maximum velocity, a Michaelis constant, and an inhibition dissociation constant for AChE activity and inhibition. These parameters enable us to determine the activity of AChE and the efficiency of the inhibitor.
Collapse
Affiliation(s)
- Tae Woog Kang
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Su-Ji Jeon
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Hye-In Kim
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Jung Hyun Park
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - DaBin Yim
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Hye-Rim Lee
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Jong-Min Ju
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Man-Jin Kim
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| | - Jong-Ho Kim
- Department of Chemical Engineering, Hanyang University , Ansan 426-791, Republic of Korea
| |
Collapse
|
6
|
Hidese R, Ataka K, Bill E, Shima S. Cu I and H 2 O 2 Inactivate and Fe II Inhibits [Fe]-Hydrogenase at Very Low Concentrations. Chembiochem 2015; 16:1861-1865. [PMID: 26136368 DOI: 10.1002/cbic.201500318] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Indexed: 11/09/2022]
Abstract
[Fe]-Hydrogenase (Hmd) catalyzes reversible hydride transfer from H2 . It harbors an iron-guanylylpyridinol as a cofactor with an FeII that is ligated to one thiolate, two COs, one acyl-C, one pyridinol-N, and solvent. Here, we report that CuI and H2 O2 inactivate Hmd (half-maximal rates at 1 μM CuI and 20 μM H2 O2 ) and that FeII inhibits the enzyme with very high affinity (Ki =40 nM). Infrared and EPR studies together with competitive inhibition studies with isocyanide indicated that CuI exerts its inhibitory effect most probably by binding to the active site iron-thiolate ligand. Using the same methods, it was found that H2 O2 binds to the active-site iron at the solvent-binding site and oxidizes FeII to FeIII . Also it was shown that FeII reversibly binds away from the active site iron, with binding being competitive to the organic hydride acceptor; this inhibition is specific for FeII and is reminiscent of that for the [FeFe]-hydrogenase second iron, which specifically interacts with H2 .
Collapse
Affiliation(s)
- Ryota Hidese
- Max-Planck-Institute für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043 Marburg (Germany)
| | - Kenichi Ataka
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany)
| | - Eckhard Bill
- Max Planck Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr (Germany)
| | - Seigo Shima
- Max-Planck-Institute für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse 10, 35043 Marburg (Germany).,PRESTO, Japan Science and Technology Agency (JST), Saitama 332-0012 (Japan)
| |
Collapse
|
7
|
Yang L, Han J, Liu W, Li J, Jiang L. Conversion of Inhibition Biosensing to Substrate-Like Biosensing for Quinalphos Selective Detection. Anal Chem 2015; 87:5270-7. [DOI: 10.1021/acs.analchem.5b00376] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Limin Yang
- State Key
Laboratory of Heavy
Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, P. R. China
| | - Juan Han
- State Key
Laboratory of Heavy
Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, P. R. China
| | - Wei Liu
- State Key
Laboratory of Heavy
Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, P. R. China
| | - Jiqiang Li
- State Key
Laboratory of Heavy
Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, P. R. China
| | - Lei Jiang
- State Key
Laboratory of Heavy
Oil Processing and Center for Bioengineering and Biotechnology, China University of Petroleum (East China), Qingdao, Shandong 266555, P. R. China
| |
Collapse
|
8
|
Wu M, Algar WR. Acceleration of proteolytic activity associated with selection of thiol ligand coatings on quantum dots. ACS APPLIED MATERIALS & INTERFACES 2015; 7:2535-2545. [PMID: 25607728 DOI: 10.1021/am507466b] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Nanoparticle bioconjugates are attractive probes for measuring the activity of hydrolytic enzymes. In these configurations, the localization of multiple copies of a hydrolase substrate to a nanoparticle scaffold has been reported to enhance apparent activity by factors of 2 to 3 compared to that for equivalent amounts of substrate in bulk solution. Here, we studied the effect of surface chemistry on protease activity using multivalent QD-peptide substrate conjugates as a model system. QDs were coated with cysteine (CYS), glutathione (GSH), dihydrolipoic acid (DHLA), or 3-mercaptopropionic acid (MPA) ligands, and thrombin and trypsin were used as model proteases. Proteolytic activity was measured for different combinations of ligand and protease using Förster resonance energy transfer (FRET)-based assays. The highest levels of activity were observed with CYS and GSH coatings, and the lowest levels of activity were observed with DHLA and MPA coatings. In all cases, proteolytic activity was accelerated compared to that for an equivalent amount of substrate in bulk solution, with up to 80- and 65-fold increases in the apparent specificity constants for thrombin and trypsin, respectively. Thrombin was more strongly affected by the QD surface chemistry, with up to a 50-fold variation in its apparent specificity constant between ligand coatings, whereas only a 5-fold variation was observed with trypsin. These trends were correlated to adsorption of the proteases on the QDs and are discussed in the context of the physicochemical properties of both components. This work clearly indicates a critical role for the nanoparticle interface in mediating substrate turnover and provides some of the strongest support to date for a so-called hopping model of activity.
Collapse
Affiliation(s)
- Miao Wu
- Department of Chemistry, University of British Columbia , 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada
| | | |
Collapse
|
9
|
Klöck C, Herrera Z, Albertelli M, Khosla C. Discovery of potent and specific dihydroisoxazole inhibitors of human transglutaminase 2. J Med Chem 2014; 57:9042-64. [PMID: 25333388 PMCID: PMC4234452 DOI: 10.1021/jm501145a] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Transglutaminase
2 (TG2) is a ubiquitously expressed enzyme that
catalyzes the posttranslational modification of glutamine residues
on protein or peptide substrates. A growing body of literature has
implicated aberrantly regulated activity of TG2 in the pathogenesis
of various human inflammatory, fibrotic, and other diseases. Taken
together with the fact that TG2 knockout mice are developmentally
and reproductively normal, there is growing interest in the potential
use of TG2 inhibitors in the treatment of these conditions. Targeted-covalent
inhibitors based on the weakly electrophilic 3-bromo-4,5-dihydroisoxazole
(DHI) scaffold have been widely used to study TG2 biology and are
well tolerated in vivo, but these compounds have only modest potency,
and their selectivity toward other transglutaminase homologues is
largely unknown. In the present work, we first profiled the selectivity
of existing inhibitors against the most pertinent TG isoforms (TG1,
TG3, and FXIIIa). Significant cross-reactivity of these small molecules
with TG1 was observed. Structure–activity and −selectivity
analyses led to the identification of modifications that improved
potency and isoform selectivity. Preliminary pharmacokinetic analysis
of the most promising analogues was also undertaken. Our new data
provides a clear basis for the rational selection of dihydroisoxazole
inhibitors as tools for in vivo biological investigation.
Collapse
Affiliation(s)
- Cornelius Klöck
- Departments of †Chemistry, ‡Chemical Engineering and §Comparative Medicine, Stanford University , MC 5080, Stanford California 94305, United States
| | | | | | | |
Collapse
|
10
|
Keillor JW, Chabot N, Roy I, Mulani A, Leogane O, Pardin C. Irreversible inhibitors of tissue transglutaminase. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 2011; 78:415-47. [PMID: 22220480 DOI: 10.1002/9781118105771.ch10] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Jeffrey W Keillor
- Department of Chemistry, University of Montréal, Montréal, QC, Canada
| | | | | | | | | | | |
Collapse
|
11
|
Alonso GA, Dominguez RB, Marty JL, Muñoz R. An approach to an inhibition electronic tongue to detect on-line organophosphorus insecticides using a computer controlled multi-commuted flow system. SENSORS 2011; 11:3791-802. [PMID: 22163822 PMCID: PMC3231336 DOI: 10.3390/s110403791] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 03/22/2011] [Accepted: 03/24/2011] [Indexed: 11/16/2022]
Abstract
An approach to an inhibition bioelectronic tongue is presented. The work is focused on development of an automated flow system to carry out experimental assays, a custom potentiostat to measure the response from an enzymatic biosensor, and an inhibition protocol which allows on-line detections. A Multi-commuted Flow Analysis system (MCFA) was selected and developed to carry out assays with an improved inhibition method to detect the insecticides chlorpyrifos oxon (CPO), chlorfenvinfos (CFV) and azinphos methyl-oxon (AZMO). The system manifold comprised a peristaltic pump, a set of seven electronic valves controlled by a personal computer electronic interface and software based on LabView® to control the sample dilutions into the cell. The inhibition method consists in the injection of the insecticide when the enzyme activity has reached the plateau of the current; with this method the incubation time is avoided. A potentiostat was developed to measure the response from the enzymatic biosensor. Low limits of detection of 10 nM for CPO, CFV, and AZMO were achieved.
Collapse
Affiliation(s)
- Gustavo A. Alonso
- Centro de Investigación y de Estudios Avanzados del Intituto Politecnico Nacional, Av. Instituto Politécnico Nacional 2508, Mexico; E-Mails: (R.B.D.); (R.M.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +52-55-57473800 ext. 6210
| | - Rocio B. Dominguez
- Centro de Investigación y de Estudios Avanzados del Intituto Politecnico Nacional, Av. Instituto Politécnico Nacional 2508, Mexico; E-Mails: (R.B.D.); (R.M.)
| | - Jean-Louis Marty
- Université de Perpignan Via Domitia, IMAGES EA4218, Centre de Phytopharmacie, 52 Avenue Paul Alduy, 66860 Perpignan Cedex, France; E-Mail:
| | - Roberto Muñoz
- Centro de Investigación y de Estudios Avanzados del Intituto Politecnico Nacional, Av. Instituto Politécnico Nacional 2508, Mexico; E-Mails: (R.B.D.); (R.M.)
| |
Collapse
|
12
|
Zhao P, Zhu KY, Jiang H. Heterologous expression, purification, and biochemical characterization of a greenbug (Schizaphis graminum) acetylcholinesterase encoded by a paralogous gene (ace-1). J Biochem Mol Toxicol 2010; 24:51-9. [DOI: 10.1002/jbt.20311] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
13
|
Jiang H, Liu S, Zhao P, Pope C. Recombinant expression and biochemical characterization of the catalytic domain of acetylcholinesterase-1 from the African malaria mosquito, Anopheles gambiae. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2009; 39:646-53. [PMID: 19607916 PMCID: PMC2772825 DOI: 10.1016/j.ibmb.2009.07.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/08/2009] [Accepted: 07/07/2009] [Indexed: 05/28/2023]
Abstract
Acetylcholinesterases (AChEs) and their genes from susceptible and resistant insects have been extensively studied to understand the molecular basis of target site insensitivity. Due to the existence of other resistance mechanisms, however, it can be problematic to correlate directly a mutation with the resistant phenotype. An alternative approach involves recombinant expression and characterization of highly purified wild-type and mutant AChEs, which serves as a reliable platform for studying structure-function relationships. We expressed the catalytic domain of Anopheles gambiae AChE1 (r-AgAChE1) using the baculovirus system and purified it 2,500-fold from the conditioned medium to near homogeneity. While K(M)'s of r-AgAChE1 were comparable for ATC, AbetaMTC, PTC, and BTC, V(max)'s were substantially different. The IC(50)'s for eserine, carbaryl, paraoxon, BW284C51, malaoxon, and ethopropazine were 8.3, 72.5, 83.6, 199, 328, and 6.59 x 10(4) nM, respectively. We determined kinetic constants for inhibition of r-AgAChE1 by four of these compounds. The enzyme bound eserine or paraoxon stronger than carbaryl or malaoxon. Because the covalent modification of r-AgAChE1 by eserine occurred faster than that by the other compounds, eserine is more potent than paraoxon, carbaryl, and malaoxon. Furthermore, we found that choline inhibited r-AgAChE1, a phenomenon related to the enzyme activity decrease at high concentrations of acetylcholine.
Collapse
Affiliation(s)
- Haobo Jiang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
| | | | | | | |
Collapse
|
14
|
Shenouda J, Green P, Sultatos L. An evaluation of the inhibition of human butyrylcholinesterase and acetylcholinesterase by the organophosphate chlorpyrifos oxon. Toxicol Appl Pharmacol 2009; 241:135-42. [PMID: 19699221 DOI: 10.1016/j.taap.2009.08.014] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 08/11/2009] [Accepted: 08/12/2009] [Indexed: 11/17/2022]
Abstract
Acetylcholinesterase (EC 3.1.1.7) and butyrylcholinesterase (EC 3.1.1.8) are enzymes that belong to the superfamily of alpha/beta-hydrolase fold proteins. While they share many characteristics, they also possess many important differences. For example, whereas they have about 54% amino acid sequence identity, the active site gorge of acetylcholinesterase is considerably smaller than that of butyrylcholinesterase. Moreover, both have been shown to display simple and complex kinetic mechanisms, depending on the particular substrate examined, the substrate concentration, and incubation conditions. In the current study, incubation of butyrylthiocholine in a concentration range of 0.005-3.0 mM, with 317 pM human butyrylcholinesterase in vitro, resulted in rates of production of thiocholine that were accurately described by simple Michaelis-Menten kinetics, with a K(m) of 0.10 mM. Similarly, the inhibition of butyrylcholinesterase in vitro by the organophosphate chlorpyrifos oxon was described by simple Michaelis-Menten kinetics, with a k(i) of 3048 nM(-1) h(-1), and a K(D) of 2.02 nM. In contrast to inhibition of butyrylcholinesterase, inhibition of human acetylcholinesterase by chlorpyrifos oxon in vitro followed concentration-dependent inhibition kinetics, with the k(i) increasing as the inhibitor concentration decreased. Chlorpyrifos oxon concentrations of 10 and 0.3 nM gave k(i)s of 1.2 and 19.3 nM(-1) h(-1), respectively. Although the mechanism of concentration-dependent inhibition kinetics is not known, the much smaller, more restrictive active site gorge of acetylcholinesterase almost certainly plays a role. Similarly, the much larger active site gorge of butyrylcholinesterase likely contributes to its much greater reactivity towards chlorpyrifos oxon, compared to acetylcholinesterase.
Collapse
Affiliation(s)
- Josephine Shenouda
- Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103, USA
| | | | | |
Collapse
|
15
|
Baici A, Schenker P, Wächter M, Rüedi P. 3-Fluoro-2,4-dioxa-3-phosphadecalins as Inhibitors of Acetylcholinesterase. A Reappraisal of Kinetic Mechanisms and Diagnostic Methods. Chem Biodivers 2009; 6:261-82. [DOI: 10.1002/cbdv.200800334] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
16
|
Abstract
The organophosphorus insecticides have been known for many years to cause cholinergic crisis in humans as a result of the inhibition of the critical enzyme acetylcholinesterase. The interactions of the activated, toxic insecticide metabolites (termed oxons) with acetylcholinesterase have been studied extensively for decades. However, more recent studies have suggested that the interactions of certain anticholinesterase organophosphates with acetylcholinesterase are more complex than previously thought since their inhibitory capacity has been noted to change as a function of inhibitor concentration. In the present report, chlorpyrifos oxon (O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphate) was incubated with human recombinant acetylcholinesterase in the presence of p-nitrophenyl acetate in order to better characterize kinetically the interactions of this oxon with enzyme. Determination of the dissociation constant, Kd, and the phophorylation rate constant, k2, for chlorpyrifos oxon with a range of oxon and p-nitrophenyl acetate concentrations revealed that Kd, but not k2, changed as a function of oxon concentration. Changes in p-nitrophenyl acetate concentrations did not alter these same kinetic parameters. The inhibitory capacity of chlorpyrifos oxon, as measured by ki (k2/Kd), was also affected as a result of the concentration-dependent alterations in binding affinity. These results suggest that the concentration-dependent interactions of chlorpyrifos oxon with acetylcholinesterase resulted from a different mechanism than the concentration-dependent interactions of acetylthiocholine. In the latter case, substrate bound to the peripheral anionic site of acetylcholinesterase has been shown to reduce enzyme activity by blocking the release of the product thiocholine from the active site gorge. With chlorpyrifos oxon, the rate of release of 3,5,6-trichloro-2-pyridinol is irrelevant since the active site is not available to interact with other oxon molecules after phosphorylation of Ser-203 has occurred.
Collapse
Affiliation(s)
- Lester G Sultatos
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103, USA.
| |
Collapse
|
17
|
Siegel M, Khosla C. Transglutaminase 2 inhibitors and their therapeutic role in disease states. Pharmacol Ther 2007; 115:232-45. [PMID: 17582505 PMCID: PMC1975782 DOI: 10.1016/j.pharmthera.2007.05.003] [Citation(s) in RCA: 159] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2007] [Accepted: 05/03/2007] [Indexed: 02/06/2023]
Abstract
Transglutaminase 2 (TG2) is a multi-domain, multi-functional enzyme that post-translationally modifies proteins by catalyzing the formation of intermolecular isopeptide bonds between glutamine and lysine side-chains. It plays a role in diverse biological functions, including extracellular matrix formation, integrin-mediated signaling, and signal transduction involving 7-transmembrane receptors. While some of the roles of TG2 under normal physiological conditions remain obscure, the protein is believed to participate in the pathogenesis of several unrelated diseases, including celiac sprue, neurodegenerative diseases, and certain types of cancer. A variety of small molecule and peptidomimetic inhibitors of the TG2 active site have been identified. Here, we summarize the biochemistry, biology, pharmacology and medicinal chemistry of human TG2.
Collapse
Affiliation(s)
- Matthew Siegel
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305
| | - Chaitan Khosla
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Department of Biochemistry, Stanford University, Stanford, CA 94305
| |
Collapse
|
18
|
Kaushik R, Rosenfeld CA, Sultatos L. Concentration-dependent interactions of the organophosphates chlorpyrifos oxon and methyl paraoxon with human recombinant acetylcholinesterase. Toxicol Appl Pharmacol 2007; 221:243-50. [PMID: 17467020 PMCID: PMC2034337 DOI: 10.1016/j.taap.2007.03.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 03/08/2007] [Accepted: 03/09/2007] [Indexed: 11/28/2022]
Abstract
For many decades it has been thought that oxygen analogs (oxons) of organophosphorus insecticides phosphorylate the catalytic site of acetylcholinesterase by a mechanism that follows simple Michaelis-Menten kinetics. More recently, the interactions of at least some oxons have been shown to be far more complex and likely involve binding of oxons to a second site on acetylcholinesterase that modulates the inhibitory capacity of other oxon molecules at the catalytic site. The current study has investigated the interactions of chlorpyrifos oxon and methyl paraoxon with human recombinant acetylcholinesterase. Both chlorpyrifos oxon and methyl paraoxon were found to have k(i)'s that change as a function of oxon concentration. Furthermore, 10 nM chlorpyrifos oxon resulted in a transient increase in acetylthiocholine hydrolysis, followed by inhibition. Moreover, in the presence of 100 nM chlorpyrifos oxon, acetylthiocholine was found to influence both the K(d) (binding affinity) and k(2) (phosphorylation constant) of this oxon. Collectively, these results demonstrate that the interactions of chlorpyrifos oxon and methyl paraoxon with acetylcholinesterase cannot be described by simple Michaelis-Menten kinetics but instead support the hypothesis that these oxons bind to a secondary site on acetylcholinesterase, leading to activation/inhibition of the catalytic site, depending on the nature of the substrate and inhibitor. Additionally, these data raise questions regarding the adequacy of estimating risk of low levels of insecticide exposure from direct extrapolation of insecticide dose-response curves since the capacity of individual oxon molecules at low oxon levels could be greater than individual oxon molecules in vivo associated with the dose-response curve.
Collapse
Affiliation(s)
- R. Kaushik
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103
| | - Clint A. Rosenfeld
- Drug Metabolism and Pharmacokinetics, Schering-Plough Research Institute, Lafayette, New Jersey 07843
| | - L.G. Sultatos
- Department of Pharmacology and Physiology, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, New Jersey 07103
- Corresponding Author, T: 973-972-6612, Fax: 973-972-4554,
| |
Collapse
|
19
|
Watts RE, Siegel M, Khosla C. Structure-activity relationship analysis of the selective inhibition of transglutaminase 2 by dihydroisoxazoles. J Med Chem 2007; 49:7493-501. [PMID: 17149878 PMCID: PMC2526180 DOI: 10.1021/jm060839a] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Human transglutaminase 2 (TG2) is believed to play an important role in the pathogenesis of various human disorders including celiac sprue, certain neurological diseases, and some types of cancer. Selective inhibition of TG2 should therefore enable further investigation of its role in physiology and disease and may lead to effective clinical treatment. Recently we showed that certain 3-halo-4-,5-dihydroisoxazole containing compounds are selective inhibitors of human TG2 with promising pharmacological activities. Here, we present definitive evidence that this class of compounds targets the active site of human TG2. Structure-activity relationship studies have provided insights into the structural prerequisites for selectivity and have led to the discovery of an inhibitor with about 50-fold higher activity than a prototypical dihydroisoxazole inhibitor with good in vivo activity. A method for preparing enantiomerically enriched analogues was also developed. Our studies show that the 5-(S)-dihydroisoxazole is a markedly better inhibitor of human TG2 than its 5-(R) stereoisomer.
Collapse
Affiliation(s)
- R Edward Watts
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | | | | |
Collapse
|
20
|
Turdean G, Popescu IC, Oniciu L. Biocapteurs ampérométriques à cholinestérases pour la détermination des pesticides organophosphorés. CAN J CHEM 2002. [DOI: 10.1139/v02-021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study is a comparative presentation of the different types of the amperometric biosensors based on cholinesterases for the determination of organophosphorous pesticides using the bibliographical information of the last 20 years. The study contains the presentation of the structure and properties of the cholinesterases, the main reactions implied in the functioning of the amperometric biosensors, their applications and factors influencing the detection or (and) the inhibition process. The detection limit of the mono- or bi-enzymatic amperometric biosensors are relatively higher than those corresponding with the immunobiosensors or with gas and liquid chromatography, which are still considered as the reference methods. As shown, for many other amperometric biosensors, the MichaelisMenten's kinetic treatment used for reactions catalyzed by free enzymes can be extended to describe the response of amperometric biosensors based on immobilized cholinesterases. The positive compromise between advantages and drawbacks, as well as the "soft" experimental conditions, point to the amperometric monoenzymatic bioelectrode, as an attractive analytical tool for the detection of organophosphorous pesticides.Key words: amperometric biosensor, acetylcholinesterase, organophosphorous pesticides, kinetic, inhibition.
Collapse
|
21
|
Jenkins DM, Delwiche MJ, DePeters EJ, BonDurant RH. Refinement of the pressure assay for milk urea nitrogen. J Dairy Sci 2000; 83:2042-8. [PMID: 11003237 DOI: 10.3168/jds.s0022-0302(00)75085-5] [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: 11/19/2022]
Abstract
We report improvements in the application of a pressure-based assay for urea. The assay involved the enzymatic hydrolysis of urea and subsequent measurement of CO2 partial pressure. Effects of the preservative bronopol on the assay and their implications for laboratory applications are discussed. A method of remediating these effects with cysteine is described. A method is also described wherein these additives can be used to prepare standards of known urea concentration in milk. The improved assay can be used to measure urea N in unadulterated milk or in bronopol preserved milk with an accuracy of +/-0.7 mg/dl (0.25 mM) in the range from 0 to 30 mg/dl (0 to 10.7 mM).
Collapse
Affiliation(s)
- D M Jenkins
- Department of Biological and Agricultural Engineering, University of California at Davis, 95616, USA
| | | | | | | |
Collapse
|
22
|
Kati WM, Sham HL, McCall JO, Montgomery DA, Wang GT, Rosenbrook W, Miesbauer L, Buko A, Norbeck DW. Inhibition of 3C protease from human rhinovirus strain 1B by peptidyl bromomethylketonehydrazides. Arch Biochem Biophys 1999; 362:363-75. [PMID: 9989947 DOI: 10.1006/abbi.1998.1038] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The gene coding for the 3C protease from human rhinovirus strain 1B was efficiently expressed in an Escherichia coli strain which also overexpressed the rare argU tRNA. The protease was isolated from inclusion bodies, refolded, and exhibited a kcat/Km = 3280 M-1 s-1 using an internally quenched peptidyl fluorogenic substrate. This continuous fluorogenic assay was used to measure the kinetics of 3C protease inhibition by several conventional peptidyl chloromethylketones as well as a novel series of compounds, the bromomethylketonehydrazides. Compounds containing the bromomethylketonehydrazide backbone and a glutamine-like side chain at the P1 position were potent, time-dependent inhibitors of rhinovirus 3C protease with kinact/Kinact values as high as 23,400 M-1 s-1. The inhibitory activity of compounds containing modified P1 side chains suggests that the interactions between the P1 carboxamide group and the 3C protease contributes at least 30-fold to the kinact/Kinact rate constants for bromomethylketonehydrazide inhibition of 3C protease. Electrospray ionization mass spectrometry measurements of the molecular weights of native and inhibited 3C protease have established an inhibitory mechanism involving formation of a covalent adduct between the enzyme and the inhibitor with the loss of a bromide ion from the bromomethylketonehydrazide. Tryptic digestion of bromomethylketonehydrazide-inhibited 3C protease established adduct formation to a peptide corresponding to residues 145-154, a region which contains the active site cysteine-148 residue. The bromomethylketonehydrazides were fairly weak inhibitors of chymotrypsin, human elastase, and cathepsin B and several of these compounds also showed evidence for inhibition of human rhinovirus 1B replication in cell culture.
Collapse
Affiliation(s)
- W M Kati
- Pharmaceutical Products Division, Abbott Laboratories, 200 Abbott Park Road, Abbott Park, Illinois, 60064-3500, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
23
|
|
24
|
Schiller MR, Holmes LD, Boeker EA. Analysis of wild-type and mutant aspartate aminotransferases using integrated rate equations. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1297:17-27. [PMID: 8841376 DOI: 10.1016/0167-4838(96)00083-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A general integrated rate equation was fit to reaction progress curves catalyzed by wild-type E. coli aspartate aminotransferase and the site-specific mutant enzymes, H193Q and Y70F. A nonlinear step-regression code, revised for this study selected from all kinetic constants in a general integrated rate equation for all unbranched enzyme mechanisms with stoichiometries upto two substrates and two products including terms for substrate inhibitions and that of an exogenous inhibitor. For each aspartate aminotransferase enzyme studied only kinetic constants consistent with a substituted enzyme mechanism were found statistically significant, thus the enzyme mechanism and sources of inhibition were determined objectively by statistics. The kinetic constants for wild-type and Y70F aspartate aminotransferase were similar to those previously reported indicating the validity of the integrated rate equation analysis. Minor changes in kinetic constants were observed for the H193Q mutant enzyme suggesting that the catalytic effects of the electrostatic hydrogen bonding network extending from the pyridine nitrogen of the cofactor through Asp-222, His-189 ends prior to His-193.
Collapse
Affiliation(s)
- M R Schiller
- Department of Chemistry and Biochemistry, Utah State University, Logan 84322, USA.
| | | | | |
Collapse
|
25
|
Manjabacas MC, Valero E, García-Moreno M, Garrido C, Varón R. Kinetics of an autocatalytic zymogen reaction in the presence of an inhibitor coupled to a monitoring reaction. Bull Math Biol 1996; 58:19-41. [PMID: 8819752 DOI: 10.1007/bf02458280] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A global kinetic analysis of a model consisting of an autocatalytic zymogen-activation process, in which an irreversible inhibitor competes with the zymogen for the active site of the proteinase, and a monitoring coupled reaction, in which the enzyme acts upon one of its substrates, is presented. This analysis is based on the progress curves of any of the two products released in the monitoring reaction. The general solution is applied to an important particular case in which rapid equilibrium conditions prevail. Finally, we suggest a procedure to predict whether the inhibition or activation route dominates in the steady state of the system. These results generalize our previous analysis of simpler mechanisms.
Collapse
Affiliation(s)
- M C Manjabacas
- Departamento de Química-Física, Escuela Universitaria Polítecnica deAlbacete, Universidad de Castilla-La Mancha, Spain
| | | | | | | | | |
Collapse
|
26
|
Navarro-Lozano MJ, Valero E, Varon R, Garcia-Carmona F. Kinetic study of an enzyme-catalysed reaction in the presence of novel irreversible-type inhibitors that react with the product of enzymatic catalysis. Bull Math Biol 1995; 57:157-68. [PMID: 7833851 DOI: 10.1007/bf02458321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In the present paper a kinetic study is made of the behaviour of a Michaelis-Menten enzyme-catalysed reaction in the presence of irreversible inhibitors rendered unstable in the medium by their reaction with the product of enzymatic catalysis. A general mechanism involving competitive, non-competitive, uncompetitive and mixed irreversible inhibition with one or two steps has been analysed. The differential equation that describes the kinetics of the reaction is non-linear and computer simulations of its dynamic behaviour are presented. The results obtained show that the systems studied here present kinetic co-operativity for a target enzyme that follows the simple Michaelis-Menten mechanism in its action on the substrate, except in the case of an uncompetitive-type inhibitor.
Collapse
Affiliation(s)
- M J Navarro-Lozano
- Departmento de Química-Física, Escuela Universitaria Politécnica de Albacete, Universidad de Castilla-La Mancha, Spain
| | | | | | | |
Collapse
|
27
|
Pitari G, Maurizi G, Ascenzi P, Ricci G, Duprè S. A kinetic study on pantetheinase inhibition by disulfides. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 226:81-6. [PMID: 7957261 DOI: 10.1111/j.1432-1033.1994.tb20028.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The mammalian enzyme pantetheinase, which hydrolyzes pantetheine to pantothenic acid and cysteamine, is inhibited by many thiol reagents and activated by thiols. Two thiol groups of different reactivity and accessibility are involved in the catalytic process [Ricci, G., Nardini, M., Chiaraluce, R., Duprè, S. & Cavallini, D. (1986) Biochim. Biophys. Acta 870, 82-91]. The inhibition kinetics by some natural and synthetic disulfides [pantethine, cystamine, 5,5'-dithiobis(2-nitrobenzoic acid), 4,4'-dithiodipyridine and oxidized mercaptoethanol] has been studied by two experimental approaches, either by monitoring activity after incubation of the enzyme with the inhibitor or by determining the progress curves in the presence of substrate and inhibitor. Data reported here indicate that pantetheinase reacts irreversibly with various disulfides in a time-dependent manner with the formation of a mixed disulfide apparently preceeded by a conformational change, giving a modified E* form with new kinetic parameters. This modified form may be further competitively inhibited by disulfides interacting with the enzyme at the active site.
Collapse
Affiliation(s)
- G Pitari
- Dipartimento di Biologia di base ed applicata, Università de L'Aquila, Italy
| | | | | | | | | |
Collapse
|
28
|
Garrido-del Solo C, García-Cánovas F, Havsteen BH, Varón-Castellanos R. Kinetic analysis of a Michaelis-Menten mechanism in which the enzyme is unstable. Biochem J 1993; 294 ( Pt 2):459-64. [PMID: 8373361 PMCID: PMC1134476 DOI: 10.1042/bj2940459] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A kinetic analysis of the Michaelis-Menten mechanism is made for the cases in which the free enzyme, or the enzyme-substrate complex, or both, are unstable, either spontaneously or as a result of the addition of a reagent. The explicit time-course equations of all of the species involved has been derived under conditions of limiting enzyme concentration. The validity of these equations has been checked by using numerical simulations. An experimental design and a kinetic data analysis allowing the evaluation of the parameters and kinetic constants are recommended.
Collapse
Affiliation(s)
- C Garrido-del Solo
- Departamento de Química-Física, Escuela Universitaria Politécnica, Universidad de Castilla-La Mancha, Albacete, Spain
| | | | | | | |
Collapse
|
29
|
Angliker H, Shaw E, Stone SR. Synthesis of oligopeptide chloromethanes to investigate extended binding regions of proteinases: application to the interaction of fibrinogen with thrombin. Biochem J 1993; 292 ( Pt 1):261-6. [PMID: 8503855 PMCID: PMC1134298 DOI: 10.1042/bj2920261] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A method was established for the synthesis of oligopeptide chloromethanes which should be useful in the study of serine and cysteine proteinases with extended binding sites. The method involved condensation of an N-terminal peptide fragment obtained by solid-phase synthesis with a C-terminal peptide chloromethane synthesized by solution-phase chemistry. By using this procedure, oligopeptide chloromethanes of up to 16 residues were synthesized. These chloromethanes were based on the sequence of fibrinopeptide A. By using oligopeptide chloromethanes of different length, it was possible to show that the residues Asp7-Phe8-Leu9 play a crucial role in the recognition of fibrinopeptide A by thrombin. In contrast, the residues Ala1-Asp2-Ser3-Gly4-Glu5-Gly6 seem to play a minor role. Substitution of valine for Gly12, which occurs in a dysfibrinogenaemia, markedly decreased the rate of inactivation of thrombin by the oligopeptide chloromethane. The results are discussed in terms of the recently published structure of the complex between human thrombin and a chloromethane inhibitor based on fibrinopeptide A.
Collapse
Affiliation(s)
- H Angliker
- Friedrich Miescher-Institut, Basel, Switzerland
| | | | | |
Collapse
|
30
|
Synthesis and inhibiting activities of 1-peptidyl-2-haloacetyl hydrazines toward cathepsin B and calpains. Eur J Med Chem 1993. [DOI: 10.1016/0223-5234(93)90147-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
31
|
Giordano C, Calabretta R, Gallina C, Consalvi V, Scandurra R, Noya FC, Franchini C. Iodo and diiodotyrosine epoxysuccinyl derivatives as selective inhibitors of cathepsin B. Eur J Med Chem 1993. [DOI: 10.1016/0223-5234(93)90046-h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
|
32
|
N-Haloacetyl-amino-acid amides as active-site-directed inhibitors of papain and cathepsin B. Eur J Med Chem 1992. [DOI: 10.1016/0223-5234(92)90018-v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
33
|
Cléry C, Masson P, Heiber-Langer I, Balny C. Soman inhibition of butyrylcholinesterase in the presence of substrate: pressure and temperature perturbations. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1159:295-302. [PMID: 1390935 DOI: 10.1016/0167-4838(92)90059-m] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Irreversible inhibition of butyrylcholinesterase by soman was studied in the presence of the substrate (o-nitrophenyl butyrate). Inhibition was found of the competitive complexing type. Study at different temperatures and pressures showed that the behavior of the enzyme differs from that of the inhibitor-free enzyme. In the absence of inhibitor, enzyme kinetics displayed a non-linear temperature dependence with a break at 21 degrees C. In the presence of a non-inhibitor structural analog of soman (pinacolyl dimethylphosphinate and methyl dimethylphosphinate), the Arrhenius plot break is slightly shifted (18 degrees C). On the other hand, in the presence of soman this break is abolished. The pressure-dependence of the substrate hydrolysis revealed also differences between the native enzyme and the enzyme in the presence of soman: the sign and magnitude of the apparent activation volume (delta V not equal to) were different for the two reactions. Beyond 300 bar, in the presence of soman, a plateau (delta V not equal to approx. 0) was observed over a large pressure range depending on temperature. Such a behavior with respect to temperature and pressure can reflect a soman-induced enzyme conformational state. Thus, temperature and pressure perturbations of the kinetics allow to complete the inhibition scheme of butyrylcholinesterase by soman. Our data suggest that upon soman binding, the enzyme undergoes a long-lived soman-induced-fit conformational change preceding the phosphonylation step. However, an alternative hypothesis according to which the enzyme processes a secondary soman-binding site cannot be ruled out.
Collapse
Affiliation(s)
- C Cléry
- Centre de Recherches du Service de Santé des Armées, La Tronche, France
| | | | | | | |
Collapse
|
34
|
Chang TC, Huang SM, Huang TM, Chang GG. Human placental alkaline phosphatase. An improved purification procedure and kinetic studies. EUROPEAN JOURNAL OF BIOCHEMISTRY 1992; 209:241-7. [PMID: 1396702 DOI: 10.1111/j.1432-1033.1992.tb17282.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
An improved method for the purification of human placental alkaline phosphatase is described. The partially purified enzyme from Sigma was further purified by successive Concanavalin A-Sepharose and Q-Sepharose chromatography. The whole procedure may be completed in one working day. Highly purified enzyme was obtained with a 39% yield. The intrinsic fluorescence of the enzyme decreased at elevated temperature. The conformation of the enzyme molecule was studied by the fluorescence quenching technique. Upward Stern-Volmer plots were obtained for the quenching data which suggested that, in addition to collisional quenching, static quenching was involved in the quenching mechanism. The dynamic and static quenching constants were found to be 0.7 +/- 0.16 M-1 and 0.44 +/- 0.1 M-1, respectively, using acrylamide as the quenching agent. The corresponding values were 0.43 +/- 0.23 M-1 and 0.84 +/- 0.18 M-1, respectively, with KI as the quenching agent. Mg2+ and PO4(3-) induced protein conformational changes which altered both the dynamic and static quenching constants. Mg2+ was found to be a non-essential activator for the placental alkaline-phosphatase-catalyzed hydrolysis of 4-nitrophenyl phosphate. At pH 9.8, Mg2+ increased Vmax by 1.2-fold without affecting the Kd of the substrate. The tetranitromethane-modified enzyme showed slower migration toward the anode on electrophoresis and increased Kd for Mg2+.
Collapse
Affiliation(s)
- T C Chang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | | | | | | |
Collapse
|
35
|
Chang GG, Huang TM, Wang JK, Lee HJ, Chou WY, Meng CL. Kinetic mechanism of the cytosolic malic enzyme from human breast cancer cell line. Arch Biochem Biophys 1992; 296:468-73. [PMID: 1632639 DOI: 10.1016/0003-9861(92)90599-r] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The kinetic mechanism of the cytosolic NADP(+)-dependent malic enzyme from cultured human breast cancer cell line was studied by steady-state kinetics. In the direction of oxidative decarboxylation, the initial-velocity and product-inhibition studies indicate that the enzyme reaction follows a sequential ordered Bi-Ter kinetic mechanism with NADP+ as the leading substrate followed by L-malate. The products are released in the order of CO2, pyruvate, and NADPH. The enzyme is unstable at high salt concentration and elevated temperature. However, it is stable for at least 20 min under the assay conditions. Tartronate (2-hydroxymalonate) was found to be a noncompetitive inhibitor for the enzyme with respect to L-malate. The kinetic mechanism of the cytosolic tumor malic enzyme is similar to that for the pigeon liver cytosolic malic enzyme but different from those for the mitochondrial enzyme from various sources.
Collapse
Affiliation(s)
- G G Chang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | | | | | | | | | | |
Collapse
|
36
|
Affiliation(s)
- S Michaelson
- Materials Research Laboratory, Defence Science and Technology Organisation, Ascot Vale, Victoria, Australia
| | | |
Collapse
|
37
|
Stone SR, Rennex D, Wikstrom P, Shaw E, Hofsteenge J. Inactivation of prolyl endopeptidase by a peptidylchloromethane. Kinetics of inactivation and identification of sites of modification. Biochem J 1991; 276 ( Pt 3):837-40. [PMID: 2064618 PMCID: PMC1151080 DOI: 10.1042/bj2760837] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The kinetics of inactivation of prolyl endopeptidase by acetyl-Ala-Ala-Pro-CH2Cl were studied by progress-curve methods in the presence of substrate. The kinetic mechanism was found to involve the formation of an initial complex between the enzyme and the chloromethane followed by an inactivation step. The substrate was shown to compete for the formation of the initial complex, indicating that binding at the active site was a prerequisite for inactivation. After reaction of the enzyme with [3H]acetyl-Ala-Ala-Pro-CH2Cl, it was possible to isolate five labelled peptides. Four of these peptides contained a cysteine residue as the site of modification, whereas the fifth peptide contained no cysteine and a histidine residue was identified as the site of modification. This residue (His-680) probably represents the active-site histidine of prolyl endopeptidase.
Collapse
Affiliation(s)
- S R Stone
- Friedrich Miescher-Institut, Basel, Switzerland
| | | | | | | | | |
Collapse
|
38
|
Khouri HE, Plouffe C, Hasnain S, Hirama T, Storer AC, Ménard R. A model to explain the pH-dependent specificity of cathepsin B-catalysed hydrolyses. Biochem J 1991; 275 ( Pt 3):751-7. [PMID: 2039451 PMCID: PMC1150117 DOI: 10.1042/bj2750751] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. Three synthetic substrates of cathepsin B (EC 3.4.22.1) with various amino acid residues at the P2 position (Cbz-Phe-Arg-NH-Mec, Cbz-Arg-Arg-NH-Mec and Cbz-Cit-Arg-NH-Mec, where Cbz represents benzyloxycarbonyl and NH-Mec represents 4-methylcoumarin-7-ylamide) were used to investigate the pH-dependency of cathepsin B-catalysed hydrolyses and to obtain information on the nature of enzyme-substrate interactions. 2. Non-linear-regression analysis of pH-activity profiles for these substrates indicates that at least four ionizable groups on cathepsin B with pKa values of 3.3, 4.55, 5.46 and greater than 7.3 can affect the rate of substrate hydrolysis. 3. Ionization of the residue with a pKa of 5.46 has a strong effect on activity towards the substrate with an arginine in P2 (8.4-fold increase in activity) but has only a moderate effect on the rate of hydrolysis with Cbz-Cit-Arg-NH-Mec (2.3-fold increase in activity) and virtually no effect with Cbz-Phe-Arg-NH-Mec. The kinetic data are consistent with this group being an acid residue with a side chain able to interact with the side chains of an arginine or a citrulline in the P2 position of a substrate. Amino acid sequence alignment and model building with the related enzyme papain (EC 3.4.22.2) suggest that Glu-245 of cathepsin B is a likely candidate. The relative importance of electrostatic and hydrophobic interactions in the S2 subsite of cathepsin B is discussed. 4. For all three substrates, activity appears after ionization of a group with a pKa of 3.3, believed to be the active-site Cys-29 of cathepsin B. The identity of the groups with pKa values of 4.55 and greater than 7.3 remains unknown.
Collapse
Affiliation(s)
- H E Khouri
- Protein Engineering Section, National Research Council Canada, Montréal, Québec
| | | | | | | | | | | |
Collapse
|
39
|
The effects of systematic errors on the analysis of irreversible enzyme inhibition progress curves. Biochem J 1991; 274 ( Pt 1):181-5. [PMID: 2001230 PMCID: PMC1149936 DOI: 10.1042/bj2740181] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The effects of errors in Km and Vmax. on the determination of the kinetic constants for the irreversible inhibition of acetylcholinesterase were determined. The results show that small errors in the values of Km and Vmax. give rise to large errors in the fitted parameters k2 and Kd. The problem may be minimized for multiple progress curves by selecting an appropriate number and distribution of inhibitor concentrations.
Collapse
|
40
|
Kinetic mechanism of the endogenous lactate dehydrogenase activity of duck epsilon-crystallin. Arch Biochem Biophys 1991; 284:285-91. [PMID: 1989512 DOI: 10.1016/0003-9861(91)90297-v] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Initial velocity, product inhibition, and substrate inhibition studies suggest that the endogenous lactate dehydrogenase activity of duck epsilon-crystallin follows an order Bi-Bi sequential mechanism. In the forward reaction (pyruvate reduction), substrate inhibition by pyruvate was uncompetitive with inhibition constant of 6.7 +/- 1.7 mM. In the reverse reaction (lactate oxidation), substrate inhibition by L-lactate was uncompetitive with inhibition constant of 158 +/- 25 mM. The cause of these inhibitions may be due to epsilon-crystallin-NAD(+)-pyruvate and epsilon-crystallin-NADH-L-lactate abortive ternary complex formation as suggested by the multiple inhibition studies. Pyruvate binds to free enzyme very poorly, with a very large dissociation constant. Bromopyruvate, fluoropyruvate, pyruvate methyl ester, and pyruvate ethyl ester are alternative substrates for pyruvate. 3-Acetylpyridine adenine dinucleotide, nicotinamide 1,N6-ethenoadenine dinucleotide, and nicotinamide hypoxanthine dinucleotide serve as alternative coenzymes for epsilon-crystallin. All the above alternative substrates or coenzymes showed an intersecting initial-velocity pattern conforming to the order Bi--Bi kinetic mechanism. Nicotinic acid adenine dinucleotide, thionicotinamide adenine dinucleotide, and 3-aminopyridine adenine dinucleotide acted as inhibitors for this enzymatic crystallin. The inhibitors were competitive versus NAD+ and noncompetitive versus L-lactate. alpha-NAD+ was a noncompetitive inhibitor with respect to the usual beta-NAD+. D-Lactate, tartronate, and oxamate were strong dead-end inhibitors for the lactate dehydrogenase activity of epsilon-crystallin. Both D-lactate and tartronate were competitive inhibitors versus L-lactate while oxamate was a competitive inhibitor versus pyruvate. We conclude that the structural requirements for the substrate and coenzyme of epsilon-crystallin are similar to those of other dehydrogenases and that the carboxamide carbonyl group of the nicotinamide moiety is important for the coenzyme activity.
Collapse
|
41
|
Gravett PS, Viljoen CC, Oosthuizen MM. Inactivation of arginine esterase E-I of Bitis gabonica venom by irreversible inhibitors including a water-soluble carbodiimide, a chloromethyl ketone and isatoic anhydride. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1991; 23:1101-10. [PMID: 1786852 DOI: 10.1016/0020-711x(91)90150-l] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. Esterase E-I from Bitis gabonica was inactivated with irreversible inhibitors which included studies with a water-soluble carbodiimide, an affinity labelling peptide and a mechanism-based inactivator. 2. The reaction with 1-ethyl-3(3-dimethylaminopropyl)-carbodiimide was biphasic and the dominant part followed saturation kinetics. At pH 5.5 a rate constant of 0.4 min-1 for inactive enzyme formation was calculated and a dissociation constant (Ki) of 0.2 M for the enzyme-inhibitor complex. 3. Inactivation with D-Phe-Pro-Arg-chloromethyl ketone indicated a two-step mechanism, for which the reaction parameters at pH 8.0 were determined. The Ki value was 0.2 microM and the inactivation rate was 2.5 min-1. 4. With isatoic anhydride pseudo-first-order kinetics was observed. At pH 8.0 a rate constant of 0.9 min-1 and a Ki of 2.0 mM were obtained. The inactivation of the enzyme was found to be governed by a group in the enzyme showing a pK value of 7.3.
Collapse
Affiliation(s)
- P S Gravett
- Health Chemical Laboratory, Department of National Health and Population Development, Pretoria, Republic of South Africa
| | | | | |
Collapse
|
42
|
Chang GG, Shiao MS, Lee KR, Wu JJ. Modification of human placental alkaline phosphatase by periodate-oxidized 1,N6-ethenoadenosine monophosphate. Biochem J 1990; 272:683-90. [PMID: 2176472 PMCID: PMC1149763 DOI: 10.1042/bj2720683] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Oxidation of 1,N6-ethenoadenosine monophosphate (epsilon AMP) with periodate cleaved the cis-diol of the ribose ring and resulted in the formation of a dialdehyde derivative (epsilon AMP-dial). At room temperature epsilon AMP-dial was unstable and underwent beta-elimination to give 4',5'-anhydro-1,N6-ethenoadenosine dialdehyde acetal (A epsilon Ado-dial). These nucleotide analogues were found to inactivate human placental alkaline phosphatase in a time- and concentration-dependent manner. epsilon AMP-dial was shown to be an affinity label for the enzyme on the basis of the following criteria. (a) Kinetics of the enzyme activity loss over a wide range of epsilon AMP-dial concentration showed a saturating phenomenon. Removal of the phosphate group made the reagent (A epsilon Ado-dial) become a general chemical modifying reagent. (b) The artificial substrate p-nitrophenyl phosphate gave substantial protection of the enzyme against inactivation. (c) epsilon AMP-dial was a substrate and a partial mixed-type inhibitor for the enzyme. Results of the inhibition and protection studies indicated that the reagent and substrate could combine with the enzyme simultaneously. Besides the phosphate-binding domain, an induced hydrophobic region is proposed for the substrate-binding site for human placental alkaline phosphatase.
Collapse
Affiliation(s)
- G G Chang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | | | | | | |
Collapse
|
43
|
Topham CM. A generalized theoretical treatment of the kinetics of an enzyme-catalysed reaction in the presence of an unstable irreversible modifier. J Theor Biol 1990; 145:547-72. [PMID: 2246902 DOI: 10.1016/s0022-5193(05)80488-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A generalized theoretical treatment of the kinetics of an enzyme-catalysed reaction in the presence of an unstable irreversible inhibitor (or activator) is presented. Analytical expressions describing the time-dependence of product formation have been derived in coefficient form amenable to non-linear regression analysis for two operationally distinct types of reaction mechanism dependent on whether the reaction of the unstable modifier (X) with either or both the free enzyme (E) and enzyme-substrate complex (ES) occurs as a simple bimolecular process, or proceeds through the intermediacy of either or both adsorptive enzyme-modifier (EX) and enzyme-modifier-substrate (EXS) complexes in what may be considered as an extension of the Botts-Morales general modifier mechanism for (stable) reversible enzyme inhibitors and activators. Special cases of both models are classified in an analogous way to the traditional naming of reversible enzyme modifications, and guidelines concerning tests of mechanism and determination of kinetic parameters are given. In particular, it has been shown that kinetic constants describing enzyme inactivation by an unstable site-specific inhibitor forming a reversible EX complex prior to covalent modification step may be determined from a single progress curve. Kinetic analysis of the extended Botts-Morales mechanism describing irreversible enzyme inactivation has demonstrated that analytical expressions describing the time-course of product formation may be derived for a stable modifier by retaining the usual steady-state assumptions regarding the fluxes around ES and EXS provided quasi-equilibrium modifier binding to E and ES is assumed, but for unstable modifiers all of the binding steps must be assumed to be at quasi-equilibrium in the steady-state, except under restrictive circumstances.
Collapse
Affiliation(s)
- C M Topham
- Department of Biochemistry, Medical College of St Bartholomew's Hospital, University of London, UK
| |
Collapse
|
44
|
Demuth HU. Recent developments in inhibiting cysteine and serine proteases. JOURNAL OF ENZYME INHIBITION 1990; 3:249-78. [PMID: 2181080 DOI: 10.3109/14756369009030375] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Some 20 years ago, affinity labelling was introduced to help gather information on active-site catalytic groups and the mechanisms of proteolytic enzymes. Now this knowledge is used to produce specific and selective inhibitors for these enzymes. The concept of "biospecific drug design" has stimulated progress in turning the inhibitors into therapeutically applicable agents. For instance, sales of antihypertensive drugs based on inhibitors of the angiotensin converting enzyme are expected to be over 2 billion US-$ in 1992. This partly illustrates the efforts made by many researchers to introduce strategies in potease inhibition for medicinal purposes. This review discusses some of the concepts.
Collapse
Affiliation(s)
- H U Demuth
- Department of Biotechnology, Martin-Luther-University, Halle-Wittenberg, Saale, German Democratic Republic
| |
Collapse
|