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Sato R, Minamihata K, Wakabayashi R, Goto M, Kamiya N. Molecular crowding elicits the acceleration of enzymatic crosslinking of macromolecular substrates. Org Biomol Chem 2023; 21:306-314. [PMID: 36342388 DOI: 10.1039/d2ob01549h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cytoplasm contains high concentrations of biomacromolecules. Protein behavior under such crowded conditions is reportedly different from that in an aqueous buffer solution, mainly owing to the effect of volume exclusion caused by the presence of macromolecules. Using a crosslinking reaction catalyzed by microbial transglutaminase (MTG) as a model, we herein systematically determined how the substrate size affects enzymatic activity in both dilute and crowded solutions of dextran. We first observed a threefold reduction in MTG-mediated crosslinking of a pair of small peptide substrates in 15 wt% dextran solution. In contrast, when proteinaceous substrates were involved, the crosslinking rates in 15 wt% dextran solutions accelerated markedly to levels comparable with the level in the absence of dextran. Our results provide new insights into the action of enzymes with regard to macromolecular substrates under crowded conditions, of which the potential utility was demonstrated by the formation of highly crosslinked protein polymers.
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Affiliation(s)
- Ryo Sato
- Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
| | - Kosuke Minamihata
- Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
| | - Rie Wakabayashi
- Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan.
| | - Masahiro Goto
- Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan. .,Division of Biotechnology, Center for Future Chemistry, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
| | - Noriho Kamiya
- Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan. .,Division of Biotechnology, Center for Future Chemistry, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
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Synthesis of Zearalenone Immunogen and Comparative Analysis of Antibody Characteristics. Int J Anal Chem 2021; 2021:7109383. [PMID: 34349801 PMCID: PMC8328739 DOI: 10.1155/2021/7109383] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/20/2021] [Accepted: 07/12/2021] [Indexed: 11/18/2022] Open
Abstract
Background This study aimed to explore the zearalenone (ZEN) immunogen synthesis method, immunogenicity, and antibody characteristics and to lay a foundation for the establishment of immunoassay methods for ZEN single residue and ZEN and its analogs total residue. Methods Based on the molecular structure and active sites of ZEN, oxime active ester (OAE), condensation mixed anhydride (CMA), formaldehyde (FA), and 1,4-butanediol diglycidyl ether method (BDE) were designed and used for immunogen (ZEN-BSA) synthesis. The immunogens were identified by infrared (IR) and ultraviolet (UV) spectra and gel electrophoresis (SDS-PAGE) and were then used to immunize Balb/c mice to prepare ZEN polyclonal antibody (ZEN pAb). The titers and sensitivity of the ZEN pAb were determined by indirect noncompetitive ELISA (inELISA) and indirect competitive ELISA (icELISA), respectively, and its specificity was assessed by the cross-reaction test (CR). Results ZEN-BSA was successfully synthesized, and the molecular binding ratios of ZEN to BSA were 17.2 : 1 (OAE), 14.6 : 1 (CMA), 9.7 : 1 (FA), and 8.3 : 1 (BDE), respectively. The highest inELISA titers of ZEN pAb of each group were 1 : (6.4 × 103) (OAE), 1 : (3.2 × 103) (CMA), 1 : (1.6 × 103) (FA), and 1 : (1.6 × 103) (BDE), respectively. The 50% inhibition concentrations (IC50) for ZEN by icELISA of each group were 11.67 μg/L (OAE), 16.29 μg/L (CMA), 20.92 μg/L (FA) and 24.36 μg/L (BDE), respectively. ZEN pAb from the mice immunized with ZEN-BSA (OAE) and ZEN-BSA (CMA) had class broad specificity to ZEN and its analogs. The CRs of ZEN pAb with α-ZAL, β-ZAL, α-ZOL, β-ZOL, and ZON were 36.53%, 16.98%, 64.33%, 20.16%, and 10.66%, respectively. ZEN pAb from the mice immunized with ZEN-BSA (FA) and ZEN-BSA (BDE) had high specificity for ZEN. The CRs of ZEN pAb with its analogs were all less than 1.0%. Conclusion This study demonstrated that the preparation of the class broad-specificity antibodies of ZEN and its analogs can be achieved by immunizing animals with the immunogen ZEN-BSA prepared by the OAE method, while the preparation of highly specific antibodies can be achieved by immunizing animals with the immunogen ZEN-BSA prepared by the FA method. These findings lay the material and technical foundation for immunoassay of ZEN single residue and ZEN and its analogs total residue.
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Walsh SJ, Bargh JD, Dannheim FM, Hanby AR, Seki H, Counsell AJ, Ou X, Fowler E, Ashman N, Takada Y, Isidro-Llobet A, Parker JS, Carroll JS, Spring DR. Site-selective modification strategies in antibody-drug conjugates. Chem Soc Rev 2021; 50:1305-1353. [PMID: 33290462 DOI: 10.1039/d0cs00310g] [Citation(s) in RCA: 205] [Impact Index Per Article: 68.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Antibody-drug conjugates (ADCs) harness the highly specific targeting capabilities of an antibody to deliver a cytotoxic payload to specific cell types. They have garnered widespread interest in drug discovery, particularly in oncology, as discrimination between healthy and malignant tissues or cells can be achieved. Nine ADCs have received approval from the US Food and Drug Administration and more than 80 others are currently undergoing clinical investigations for a range of solid tumours and haematological malignancies. Extensive research over the past decade has highlighted the critical nature of the linkage strategy adopted to attach the payload to the antibody. Whilst early generation ADCs were primarily synthesised as heterogeneous mixtures, these were found to have sub-optimal pharmacokinetics, stability, tolerability and/or efficacy. Efforts have now shifted towards generating homogeneous constructs with precise drug loading and predetermined, controlled sites of attachment. Homogeneous ADCs have repeatedly demonstrated superior overall pharmacological profiles compared to their heterogeneous counterparts. A wide range of methods have been developed in the pursuit of homogeneity, comprising chemical or enzymatic methods or a combination thereof to afford precise modification of specific amino acid or sugar residues. In this review, we discuss advances in chemical and enzymatic methods for site-specific antibody modification that result in the generation of homogeneous ADCs.
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Affiliation(s)
- Stephen J Walsh
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK.
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Park J, Lee S, Kim Y, Yoo TH. Methods to generate site-specific conjugates of antibody and protein. Bioorg Med Chem 2021; 30:115946. [DOI: 10.1016/j.bmc.2020.115946] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 12/07/2020] [Accepted: 12/09/2020] [Indexed: 02/07/2023]
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PolyTag: A peptide tag that affords scaffold-less covalent protein assembly catalyzed by microbial transglutaminase. Anal Biochem 2020; 600:113700. [DOI: 10.1016/j.ab.2020.113700] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Revised: 02/28/2020] [Accepted: 03/09/2020] [Indexed: 12/11/2022]
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Cheng Y, Liu Y, Liba BD, Ghodssi R, Rubloff GW, Bentley WE, Payne GF. Biofabricating the Bio-Device Interface Using Biological Materials and Mechanisms. Biofabrication 2013. [DOI: 10.1016/b978-1-4557-2852-7.00012-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Higher susceptibility to amyloid fibril formation of the recombinant ovine prion protein modified by transglutaminase. Biochim Biophys Acta Mol Basis Dis 2012; 1822:1509-15. [DOI: 10.1016/j.bbadis.2012.06.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 05/09/2012] [Accepted: 06/04/2012] [Indexed: 11/21/2022]
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Macierzanka A, Bordron F, Rigby NM, Mills EC, Lille M, Poutanen K, Mackie AR. Transglutaminase cross-linking kinetics of sodium caseinate is changed after emulsification. Food Hydrocoll 2011. [DOI: 10.1016/j.foodhyd.2010.07.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Liu Y, Kim E, Ghodssi R, Rubloff GW, Culver JN, Bentley WE, Payne GF. Biofabrication to build the biology–device interface. Biofabrication 2010; 2:022002. [DOI: 10.1088/1758-5082/2/2/022002] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Di Pierro P, Mariniello L, Sorrentino A, Villalonga R, Chico B, Porta R. Putrescine-polysaccharide conjugates as transglutaminase substrates and their possible use in producing crosslinked films. Amino Acids 2009; 38:669-75. [PMID: 19960213 DOI: 10.1007/s00726-009-0427-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Accepted: 09/10/2009] [Indexed: 11/25/2022]
Abstract
Putrescine (1,4-diaminobutane) was covalently linked to alginate and low-methoxyl pectin to synthesize new aminated polysaccharides. Both putrescine-pectin and -alginate conjugates, although the latter at higher concentrations, were found to be able to act as effective acyl acceptor transglutaminase substrates in vitro using both dimethylated casein and soy flour proteins as acyl donors. Monodansylcadaverine, a well known acyl acceptor transglutaminase substrate, dose-dependently counteracted the covalent binding of the aminated polysaccharides to the proteins. Putrescine-pectin conjugate was also tested to prepare, in combination with soy flour proteins, edible films in the presence of purified microbial transglutaminase. Characterization of the enzymatically crosslinked films showed a significant decreased water vapor permeability, with respect to the ones obtained with non-aminated pectin in the presence of transglutaminase, as well as improved mechanical properties, such as high extensibility. Possible biotechnological applications of hydrocolloid films containing putrescine-polysaccharide derivatives enzymatically crosslinked to proteins were suggested.
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Affiliation(s)
- Prospero Di Pierro
- Department of Food Science, University of Naples "Federico II", Portici, Naples, Italy
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de Souza CFV, Rodrigues RC, Ayub MAZ. Effects of oxygen volumetric mass transfer coefficient on transglutaminase production by Bacillus circulans BL32. BIOTECHNOL BIOPROC E 2009. [DOI: 10.1007/s12257-008-0076-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Yang X, Shi XW, Liu Y, Bentley WE, Payne GF. Orthogonal enzymatic reactions for the assembly of proteins at electrode addresses. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:338-44. [PMID: 19115870 DOI: 10.1021/la802618q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The ability to interface proteins to device surfaces is important for a range of applications. Here, we enlist the unique capabilities of enzymes and biologically derived polymers to assemble target proteins to electrode addresses. First, the stimuli-responsive aminopolysaccharide chitosan is directed to assemble at the electrode address in response to electrode-imposed signals. The electrodeposited chitosan film serves as the biodevice interface for subsequent protein assembly. Next, tyrosinase is used to catalyze grafting of a protein or peptide tether to the chitosan film. Finally, microbial transglutaminase (mTG) catalyzes the assembly of target proteins to the tether. mTG covalently links proteins through their glutamine (Gln) and lysine (Lys) residues. Since Gln and Lys residues of globular proteins are often inaccessible to mTG, we engineered our target proteins to have fusion tags with added Gln or Lys residues. This assembly method employs the electrical signal to confer spatial selectivity (during chitosan electrodeposition) and employs the enzymes to confer chemical selectivity (i.e., amino acid residue selectivity). Further, this method is mild, since no reactive reagents or protection steps are required, and all steps are performed in aqueous solution. These results demonstrate the potential for employing biological materials and mechanisms to biofabricate the biodevice interface.
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Affiliation(s)
- Xiaohua Yang
- Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Sciences Building, College Park, Maryland 20742, USA
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Tominaga J, Kemori Y, Tanaka Y, Maruyama T, Kamiya N, Goto M. An enzymatic method for site-specific labeling of recombinant proteins with oligonucleotides. Chem Commun (Camb) 2006:401-3. [PMID: 17220984 DOI: 10.1039/b613793h] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
DNA was site-specifically conjugated to a substrate peptide of microbial transglutaminase fused to the N- or C-terminus of target proteins without the loss of the proteins' functions of interest.
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Affiliation(s)
- Jo Tominaga
- Department of Applied Chemistry, Graduate School of Engineering, 744 Motooka, Fukuoka, 819-0395, Japan
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Di Pierro P, Chico B, Villalonga R, Mariniello L, Damiao AE, Masi P, Porta R. Chitosan-whey protein edible films produced in the absence or presence of transglutaminase: analysis of their mechanical and barrier properties. Biomacromolecules 2006; 7:744-9. [PMID: 16529409 DOI: 10.1021/bm050661u] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chitosan-whey protein edible films with different protein concentrations were prepared in the absence or presence of microbial transglutaminase as cross-linking agent. The films prepared in the presence of the enzyme showed low solubility at a wide range of pH, a lower degree of swelling, and good biodegradability following protease treatments. The presence of transglutaminase induced also an enhancement in film mechanical resistance and a reduction in their deformability. Finally, the barrier efficiency toward oxygen and carbon dioxide was found to be markedly improved in the cross-linked films which showed also a lower permeability to water vapor. Some potential practical applications of transglutaminase-treated chitosan-whey protein films are suggested.
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Affiliation(s)
- Prospero Di Pierro
- Dipartimento di Scienza degli Alimenti, Universita' di Napoli Federico II, Parco Gussone 80055, Portici, Naples, Italy
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Yi H, Wu LQ, Bentley WE, Ghodssi R, Rubloff GW, Culver JN, Payne GF. Biofabrication with Chitosan. Biomacromolecules 2005; 6:2881-94. [PMID: 16283704 DOI: 10.1021/bm050410l] [Citation(s) in RCA: 438] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The traditional motivation for integrating biological components into microfabricated devices has been to create biosensors that meld the molecular recognition capabilities of biology with the signal processing capabilities of electronic devices. However, a different motivation is emerging; biological components are being explored to radically change how fabrication is achieved at the micro- and nanoscales. Here we review biofabrication, the use of biological materials for fabrication, and focus on three specific biofabrication approaches: directed assembly, where localized external stimuli are employed to guide assembly; enzymatic assembly, where selective biocatalysts are enlisted to build macromolecular structure; and self-assembly, where information internal to the biological material guides its own assembly. Also reviewed are recent results with the aminopolysaccharide chitosan, a material that offers a combination of properties uniquely suited for biofabrication. In particular, chitosan can be directed to assemble in response to locally applied electrical signals, and the chitosan backbone provides sites that can be employed for the assembly of proteins, nucleic acids, and virus particles.
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Affiliation(s)
- Hyunmin Yi
- Center for Biosystems Research, University of Maryland Biotechnology Institute, 5115 Plant Sciences Building, College Park, Maryland 20742, USA
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Takazawa T, Kamiya N, Ueda H, Nagamune T. Enzymatic labeling of a single chain variable fragment of an antibody with alkaline phosphatase by microbial transglutaminase. Biotechnol Bioeng 2004; 86:399-404. [PMID: 15112292 DOI: 10.1002/bit.20019] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Functional cross-linking of a single chain Fv fragment of anti-hen egg-white lysozyme antibody (scFv) and alkaline phosphatase (AP) was explored using microbial transglutaminase (MTG) from Streptomyces mobaraensis. A specific peptidyl linker for MTG was genetically fused to the N-terminus of each protein and the resultant proteins were obtained separately by bacterial expression. The recombinant peptide-tagged scFv and AP were site-specifically cross-linked by MTG through the extra peptidyl linkers in vitro, which mainly yielded the heterodimer (i.e., scFv-AP conjugate). The enzymatic cross-linking reaction had little influence on either the antigen-binding ability of the scFv moiety or the enzymatic activity of the AP moiety of the conjugate, allowing use within an enzyme-linked immunosorbent assay. The results obtained suggest that the enzymatic approach with MTG facilitates the posttranslational construction of functional fusion proteins.
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Affiliation(s)
- Takeshi Takazawa
- Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Villalonga R, Fernández M, Fragoso A, Cao R, Di Pierro P, Mariniello L, Porta R. Transglutaminase-catalyzed synthesis of trypsin-cyclodextrin conjugates: kinetics and stability properties. Biotechnol Bioeng 2003; 81:732-7. [PMID: 12529888 DOI: 10.1002/bit.10520] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Bovine pancreatic trypsin was modified by the mono-6-amino-6-deoxy derivatives of alpha-, beta-, and gamma-cyclodextrin through a transglutaminase-catalyzed reaction. The trypsin-cyclodextrin conjugates, containing about 3 mol of oligosaccharide per mole of protein, were tested for their catalytic and stability properties. The specific esterolytic activity and the kinetics constants of trypsin were significantly improved following the transglutaminase-induced structural modifications. Trypsin-cyclodextrin conjugates were also found markedly (sixfold) more resistant to autolytic degradation at alkaline pH, and their thermal stability profile was improved by about 16 degrees C. Moreover, they were particularly resistant to heat inactivation when treated at different temperatures ranging from 45 degrees C to 70 degrees C for different periods of time.
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Affiliation(s)
- Reynaldo Villalonga
- Enzyme Technology Group, Center for Biotechnological Studies, University of Matanzas, Autopista a Varadero, Matanzas, Cuba
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Josten A, Haalck L, Spener F, Meusel M. Use of microbial transglutaminase for the enzymatic biotinylation of antibodies. J Immunol Methods 2000; 240:47-54. [PMID: 10854600 DOI: 10.1016/s0022-1759(00)00172-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Nowadays many reagents are available for the biotinylation of proteins. As most of them bind to amino groups of the protein the degree of labelling differs from batch to batch and the possibility exists that the biological activity of the target protein may be affected by the labelling procedure. In the present study we have investigated an enzymatic approach to biotinylation using microbial transglutaminase (MTGase) from Streptoverticillium mobaraense. The proposed method is particularly suitable when only a few biotin molecules need to be attached to the target proteins. The enzyme catalyses the acyl transfer reaction between gamma-carboxyamide groups and various primary amines. This was exploited for biotinylation using two amino-modified biotin derivatives, biotinamido-5-pentylamin (BIAPA) and biotinoyl-1,8-diamino-3, 6-dioxaoctane (BIDADOO) as acyl acceptors and a monoclonal IgG against the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) as the acyl donor. Kinetic studies revealed that the MTGase-mediated reaction proceeds with low velocity and is almost complete after 34 h. Conjugation ratios ranging from 1.1 to 1.9 biotins per IgG were found by mass spectrometry. To investigate the influence of antibody conjugation on antigen binding a competitive ELISA for the determination of 2,4-D employing MTGase-biotinoylated IgGs was developed. In this assay lower limits of detection of 0.3 and 1.0 microg/l of 2,4-D were achieved with BIDADOO- and BIAPA-modified antibodies, respectively.
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Affiliation(s)
- A Josten
- Institute of Chemical and Biochemical Sensor Research, Mendelstrasse Münster, Germany
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Josten A, Meusel M, Spener F, Haalck L. Enzyme immobilization via microbial transglutaminase: a method for the generation of stable sensing surfaces. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s1381-1177(99)00021-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Affiliation(s)
- D S Hage
- Department of Chemistry, University of Nebraska, Lincoln 68588-0304, USA
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Jülicher P, Haalck L, Meusel M, Cammann K, Spener F. In situ antigen immobilization for stable organic-phase immunoelectrodes. Anal Chem 1998; 70:3362-7. [PMID: 9726162 DOI: 10.1021/ac971284h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A new method based on enzymatic single-step in situ synthesis of hapten-carrier conjugates on electrodes is described yielding stable, reproducible, and reusable organic-phase immunoelectrodes (OPIEs). The electrodes developed were tailored for analyte detection in organic solvents and allow for the analysis of soil extracts without further sample processing and cleanup. Catalyzed by transglutaminase from a variant of Streptoverticillium mobaraense, the reaction proceeds in aqueous solution with and without addition of organic media in only 1.5 hours. In this study, the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was chosen as model compound and chemically amino-functionalized prior to its enzymatic immobilization. The high reproducibility of the immobilization procedure allowed for batch calibration of the immunoelectrodes. Moreover, pure methanol or treatment with diluted sulfuric acid used for regeneration studies did not disturb the hapten layer. The OPIE consists of screen-printed carbon electrodes, monoclonal anti-2,4-D antibodies, and the immunochemical recognition reaction and was optimized with regard to a high stability in organic media. For electrochemical detection, horseradish peroxidase was used as enzyme label together with H2O2 as substrate and hexacyanoferrate (II)/(III) as mediator. The OPIE showed high stability upon storage over 93 days. Response times of 17 s (t95) were found to be advantageous compared to those of other biosensors. Including the immunochemical reactions, the complete assay takes 30 min. A calibration curve for 2,4-D in 30% methanol/buffer obtained with 70 electrodes within 4 weeks revealed a detection limit of 9 mg/L, a sensitivity of 1.3 nA L mg-1 cm-2, and a repeatability of 6.8%. Although we calculated a lowered repeatability for reused electrodes of 13.4% and a slightly decreased sensitivity of 0.9 nA L mg-1 cm-2, multiple-used OPIEs could also be applied for calibration.
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Affiliation(s)
- P Jülicher
- Institut für Chemo- und Biosensorik, Münster, Germany
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