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Shakib P, Dekamin MG, Valiey E, Karami S, Dohendou M. Ultrasound-Promoted preparation and application of novel bifunctional core/shell Fe 3O 4@SiO 2@PTS-APG as a robust catalyst in the expeditious synthesis of Hantzsch esters. Sci Rep 2023; 13:8016. [PMID: 37198267 DOI: 10.1038/s41598-023-33990-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 04/21/2023] [Indexed: 05/19/2023] Open
Abstract
In this work, D-(-)-α-phenylglycine (APG)-functionalized magnetic nanocatalyst (Fe3O4@SiO2@PTS-APG) was designed and successfully prepared in order to implement the principles of green chemistry for the synthesis of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives under ultrasonic irradiation in EtOH. After preparing of the nanocatalyst, its structure was confirmed by different spectroscopic methods or techniques including Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and thermal gravimetric analysis (TGA). The performance of Fe3O4@SiO2@PTS-APG nanomaterial, as a heterogeneous catalyst for the Hantzsch condensation, was examined under ultrasonic irradiation and various conditions. The yield of products was controlled under various conditions to reach more than 84% in just 10 min, which indicates the high performance of the nanocatalyst along with the synergistic effect of ultrasonic irradiation. The structure of the products was identified by melting point as well as FTIR and 1H NMR spectroscopic methods. The Fe3O4@SiO2@PTS-APG nanocatalyst is easily prepared from commercially available, lower toxic and thermally stable precursors through a cost-effective, highly efficient and environmentally friendly procedure. The advantages of this method include simplicity of the operation, reaction under mild conditions, the use of an environmentally benign irradiation source, obtaining pure products with high efficiency in short reaction times without using a tedious path, which all of them address important green chemistry principles. Finally, a reasonable mechanism is proposed for the preparation of polyhydroquinoline (PHQ) and 1,4-dihydropyridine (1,4-DHP) derivatives in the presence of Fe3O4@SiO2@PTS-APG bifunctional magnetic nanocatalyst.
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Affiliation(s)
- Peyman Shakib
- Pharmaceutical and Heterocyclic Compounds Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran, 1684613114, Iran
| | - Mohammad G Dekamin
- Pharmaceutical and Heterocyclic Compounds Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran, 1684613114, Iran.
| | - Ehsan Valiey
- Pharmaceutical and Heterocyclic Compounds Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran, 1684613114, Iran
| | - Shahriar Karami
- Pharmaceutical and Heterocyclic Compounds Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran, 1684613114, Iran
| | - Mohammad Dohendou
- Pharmaceutical and Heterocyclic Compounds Research Laboratory, Department of Chemistry, Iran University of Science and Technology, Tehran, 1684613114, Iran
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Liu W, Luo J, Zhuang X, Shen W, Zhang Y, Li S, Hu Y, Huang H. Efficient preparation of enantiopure l-tert-leucine through immobilized penicillin G acylase catalyzed kinetic resolution in aqueous medium. Biochem Eng J 2014. [DOI: 10.1016/j.bej.2013.12.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Molecular characterization of a novel N-acetyltransferase from Chryseobacterium sp. Appl Environ Microbiol 2013; 80:1770-6. [PMID: 24375143 DOI: 10.1128/aem.03449-13] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
N-Acetyltransferase from Chryseobacterium sp. strain 5-3B is an acetyl coenzyme A (acetyl-CoA)-dependent enzyme that catalyzes the enantioselective transfer of an acetyl group from acetyl-CoA to the amino group of l-2-phenylglycine to produce (2S)-2-acetylamino-2-phenylacetic acid. We purified the enzyme from strain 5-3B and deduced the N-terminal amino acid sequence. The gene, designated natA, was cloned with two other hypothetical protein genes; the three genes probably form a 2.5-kb operon. The deduced amino acid sequence of NatA showed high levels of identity to sequences of putative N-acetyltransferases of Chryseobacterium spp. but not to other known arylamine and arylalkylamine N-acetyltransferases. Phylogenetic analysis indicated that NatA forms a distinct lineage from known N-acetyltransferases. We heterologously expressed recombinant NatA (rNatA) in Escherichia coli and purified it. rNatA showed high activity for l-2-phenylglycine and its chloro- and hydroxyl-derivatives. The Km and Vmax values for l-2-phenylglycine were 0.145 ± 0.026 mM and 43.6 ± 2.39 μmol · min(-1) · mg protein(-1), respectively. The enzyme showed low activity for 5-aminosalicylic acid and 5-hydroxytryptamine, which are reported as good substrates of a known arylamine N-acetyltransferase and an arylalkylamine N-acetyltransferase. rNatA had a comparatively broad acyl donor specificity, transferring acyl groups to l-2-phenylglycine and producing the corresponding 2-acetylamino-2-phenylacetic acids (relative activity with acetyl donors acetyl-CoA, propanoyl-CoA, butanoyl-CoA, pentanoyl-CoA, and hexanoyl-CoA, 100:108:122:10:<1).
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Enantioselective N-acetylation of 2-phenylglycine by an unusual N-acetyltransferase from Chryseobacterium sp. Biotechnol Lett 2013; 35:1053-9. [DOI: 10.1007/s10529-013-1172-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 02/26/2013] [Indexed: 10/27/2022]
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Orr V, Scharer J, Moo-Young M, Honeyman CH, Fenner D, Crossley L, Suen SY, Chou CP. Integrated development of an effective bioprocess for extracellular production of penicillin G acylase in Escherichia coli and its subsequent one-step purification. J Biotechnol 2012; 161:19-26. [DOI: 10.1016/j.jbiotec.2012.05.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 05/01/2012] [Accepted: 05/08/2012] [Indexed: 11/28/2022]
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Simultaneous clarification of Escherichia coli culture and purification of extracellularly produced penicillin G acylase using tangential flow filtration and anion-exchange membrane chromatography (TFF-AEMC). J Chromatogr B Analyt Technol Biomed Life Sci 2012; 900:71-8. [PMID: 22709629 DOI: 10.1016/j.jchromb.2012.05.039] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 05/02/2012] [Accepted: 05/06/2012] [Indexed: 11/22/2022]
Abstract
Downstream purification often represents the most cost-intensive step in the manufacturing of recombinant proteins since conventional purification processes are lengthy, technically complicated, and time-consuming. To address this issue, herein we demonstrated the simultaneous clarification and purification of the extracellularly produced recombinant protein by Escherichia coli using an integrated system of tangential flow filtration and anion exchange membrane chromatography (TFF-AEMC). After cultivation in a bench-top bioreactor with 1L working volume using the developed host/vector system for high-level expression and effective secretion of recombinant penicillin G acylase (PAC), the whole culture broth was applied directly to the established system. One-step purification of recombinant PAC was achieved based on the dual nature of membrane chromatography (i.e. microfiltration-sized pores and anion-exchange chemistry) and cross-flow operations. Most contaminant proteins in the extracellular medium were captured by the anion-exchange membrane and cells remained in the retentate, whereas extracellular PAC was purified and collected in the filtrate. The batch time for both cultivation and purification was less than 24h and recombinant PAC with high purity (19 U/mg), yield (72% recovery), and productivity (41 mg of purified PAC per liter of culture) was obtained. Due to the nature of the non-selective protein secretion system and the versatility of ion-exchange membrane chromatography, the developed system can be widely applied for effective production and purification of recombinant proteins.
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Resolution of racemic 4-hydroxy-2-cyclopentenone with immobilized penicillin G acylase. ACTA ACUST UNITED AC 2012. [DOI: 10.1016/j.tetasy.2012.05.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Chemo-enzymatic synthesis of the azasugars 1,4-dideoxyallonojirimycin and 1,4-dideoxymannojirimycin. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.tetasy.2011.10.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Grundmann P, Fessner WD. One-Pot, Regioselective Synthesis of Substituted Arylglycines for Kinetic Resolution by Penicillin G Acylase. Adv Synth Catal 2008. [DOI: 10.1002/adsc.200800203] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Gotti R, Calleri E, Massolini G, Furlanetto S, Cavrini V. Penicillin G acylase as chiral selector in CE using a pullulan-coated capillary. Electrophoresis 2006; 27:4746-54. [PMID: 17080475 DOI: 10.1002/elps.200600194] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In the present study, penicillin G acylase (PGA), an enzyme belonging to the family of hydrolases, has been investigated as chiral selector in CE using the partial filling technique. Owing to the strong disposition of PGA to be adsorbed by the inner capillary wall, permanently coated capillaries were used to diminish both the protein-wall interactions and the EOF. In particular, the silica surface of the capillary was chemically coated by an antiadhesive and an hydrophilic layer of pullulan, a high-molecular-mass homopolysaccharide. The coating procedure consisted in the silanization with glycidoxypropyltrimethoxysilane and the subsequent coupling of the hydroxyl groups of pullulan onto the silanized capillary. Using this approach, a significant EOF suppression was obtained within a wide pH range (pH 3.0-9.0); this result was very important in order to find the suitable conditions for the application of partial filling technique. The optimization of partial filling was carried out by considering the effects of different experimental conditions (buffer pH, PGA concentration, and loading duration), on the migration time and enantioresolution of rac-ketoprofen. Under the selected conditions as: 100 mM sodium phosphate buffer (pH 5.5) containing 240 microM of PGA (partial filling of 120 s at a pressure of 50 mbar), a series of acidic compounds resulted to be enantioresolved in about 10 min. The long-term stability of the proposed coating was evaluated; more than 100 injections were performed without significant loss of reproducibility.
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Affiliation(s)
- Roberto Gotti
- Department of Pharmaceutical Sciences, University of Bologna, Bologna, Italy.
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Fadnavis NW, Seo SH, Seo JH, Kim BG. Asymmetric synthesis of nonproteinogenic amino acids with l-amino acid transaminase: synthesis of (2S)-2-amino-4-oxo-4-phenylbutyric and (3E,2S)-2-amino-4-phenylbutenoic acids. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2006.07.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Escudero I, Ruiz M, Benito J, Cabezas J, Domínguez D, Coca J. Recovery of α-Phenylglycine by Micellar Extractive Ultrafiltration. Chem Eng Res Des 2006. [DOI: 10.1205/cherd.05217] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Suck K, Walter J, Menzel F, Tappe A, Kasper C, Naumann C, Zeidler R, Scheper T. Fast and efficient protein purification using membrane adsorber systems. J Biotechnol 2006; 121:361-7. [PMID: 16159680 DOI: 10.1016/j.jbiotec.2005.07.023] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 07/11/2005] [Accepted: 07/26/2005] [Indexed: 11/28/2022]
Abstract
The purification of proteins from complex cell culture samples is an essential step in proteomic research. Traditional chromatographic methods often require several steps resulting in time consuming and costly procedures. In contrast, protein purification via membrane adsorbers offers the advantage of fast and gentle but still effective isolation. In this work, we present a new method for purification of proteins from crude cell extracts via membrane adsorber based devices. This isolation procedure utilises the membranes favourable pore structure allowing high flow rates without causing high back pressure. Therefore, shear stress to fragile structures is avoided. In addition, mass transfer takes place through convection rather than diffusion, thus allowing very rapid separation processes. Based on this membrane adsorber technology the separation of two model proteins, human serum albumin (HSA) and immungluboline G (IgG) is shown. The isolation of human growth hormone (hGH) from chinese hamster ovary (CHO) cell culture supernatant was performed using a cation exchange membrane. The isolation of the enzyme penicillin acylase from the crude Escherichia coli supernatant was achieved using an anion exchange spin column within one step at a considerable purity. In summary, the membrane adsorber devices have proven to be suitable tools for the purification of proteins from different complex cell culture samples.
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Affiliation(s)
- Kirstin Suck
- Institut für Technische Chemie der Universität Hannover, Callinstrasse 3, D-30167 Hannover, Germany
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Fadnavis NW, Radhika KR, Vedamayee Devi A. Preparation of enantiomerically pure (R)- and (S)-3-amino-3-phenyl-1-propanol via resolution with immobilized penicillin G acylase. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2005.12.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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16
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Carboni C, Kierkels HG, Gardossi L, Tamiola K, Janssen DB, Quaedflieg PJ. Preparation of d-amino acids by enzymatic kinetic resolution using a mutant of penicillin-G acylase from E. coli. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2005.12.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Ming L, Zhiqiang L, Huanwen C, Shuying L, Qinhan J. Chiral quantification of D-, L-phenylglycine mixture using mass spectrometric kinetic method. JOURNAL OF MASS SPECTROMETRY : JMS 2005; 40:1072-5. [PMID: 15962347 DOI: 10.1002/jms.882] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
A novel mass spectrometric method is applied to rapid, accurate, quantitative analysis of chiral phenylglycine. Transition-metal-bound complex ions containing the chiral phenylglycine are generated by electrospray ionization mass spectrometry and subjected to collision-induced dissociation. The ratio of the two competitive dissociation rates is related to the enantiomeric composition of the mixture, allowing the determination of enantiomeric contamination in the intermediates.
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Affiliation(s)
- Li Ming
- College of Chemistry, Institute of Miniature Analytical Instrumentation, Jilin Province Research Center for Engineering and Technology of Spectral Instruments, Jilin University, Changchun 130021, China
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Carboni C, Quaedflieg PJ, Broxterman QB, Linda P, Gardossi L. Quantitative enzymatic protection of d-amino acid methyl esters by exploiting ‘relaxed’ enantioselectivity of penicillin-G amidase in organic solvent. Tetrahedron Lett 2004. [DOI: 10.1016/j.tetlet.2004.10.153] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Penicillin G hydrolysis in an electro-membrane reactor with immobilized penicillin G acylase. Enzyme Microb Technol 2003. [DOI: 10.1016/s0141-0229(03)00243-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cretich M, Pirri G, Carrea G, Chiari M. Separation of proteins in a multicompartment electrolyzer with chambers defined by a bed of gel beads. Electrophoresis 2003; 24:577-81. [PMID: 12601724 DOI: 10.1002/elps.200390067] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Multicompartment electrolyzers (MEs) with isoelectric membranes were introduced in 1989 for purifying proteins in an electric field. At the basis of ME technology there are membranes consisting of cross-linked copolymers of acrylamide and acrylamido monomers bearing protolytic groups. The technology employed for casting the membranes is an extension of the isoelectric focusing in immobilized pH gradient technique for which specific acrylamido monomers, known with the trade name of Immobiline, have been developed. However, the use of continuous membranes presents several disadvantages. Due to the mechanical characteristics of polyacrylamide, the gel must physically adhere onto a rigid support, which prevents it from collapsing. The support must have a highly porous structure in order to be permeable to proteins. The mechanical fragility of the membranes is one of the main problems that hinders the industrial scale application of ME separators. In order to overcome this problem, we propose to substitute the continuous membranes with a bed of gel beads of identical comonomer composition, obtained by an inverse emulsion polymerization process.
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Affiliation(s)
- Marina Cretich
- Istituto di Chimica del Riconoscimento Molecolare, C.N.R., Milano, Italy.
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Ruiz M, Cabezas J, Escudero I, Alvarez J, Coca J. α-Phenylglycine Extraction with Trialkylmethylammonium Chloride Free and Immobilized in a Macroporous Resin. Chem Eng Res Des 2002. [DOI: 10.1205/026387602320224094] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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22
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Selectivity of penicillin G acylase towards phenylacetic acid derivatives in amide bond synthesis in toluene. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1381-1177(01)00047-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Cretich M, Chiari M, Carrea G. Stereoselective synthesis of (S)-(+)-Naproxen catalyzed by carboxyl esterase in a multicompartment electrolyzer. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 2001; 48:247-56. [PMID: 11384761 DOI: 10.1016/s0165-022x(01)00158-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The stereoselective hydrolysis of racemic 2-substituted propionates, catalyzed by carboxyl esterase, provides a cost-competitive route to produce the optically pure, anti-inflammatory drug Naproxen. In the present work, we describe the application of the multicompartment electrolyzer reactor (ME) for the stereoselective hydrolysis of a racemic Naproxen ester, (R,S)-ethoxyethyl-[2-(6-methoxy-2-naphtyl)]propionate, catalyzed by a carboxyl esterase. The enzyme was trapped in a reactor chamber, delimited by two isoelectric membranes encompassing the pI value of the enzyme, together with the neutral substrate. After 90 min, a conversion of 45% was obtained with an enantiomeric excess of 84%. The reaction product, (S)-(+)-Naproxen, was electrophoretically removed in continuous from the reaction chamber and collected in a contiguous, more acidic chamber, separated from the enzyme and from the unreacted substrate. Moreover, at the end of the reaction, it was possible to recover the enzyme from the reactor and use it again.
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Affiliation(s)
- M Cretich
- Institute of Biocatalysis and Molecular Recognition, CNR, Via Mario Bianco, 9, 20131, Milan, Italy
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van Langen L, Oosthoek N, Guranda D, van Rantwijk F, Švedas V, Sheldon R. Penicillin acylase-catalyzed resolution of amines in aqueous organic solvents. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0957-4166(00)00442-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Castelletti L, Bossi A, Righetti PG. Characterization of polymeric buffers for operating membrane-trapped enzyme reactors in an electric field. Biotechnol Bioeng 2000. [DOI: 10.1002/(sici)1097-0290(20000705)69:1<39::aid-bit5>3.0.co;2-l] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Basso A, Braiuca P, De Martin L, Ebert C, Gardossi L, Linda P. d-Phenylglycine and d-4-hydroxyphenylglycine methyl esters via penicillin G acylase catalysed resolution in organic solvents. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0957-4166(00)00129-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Bossi A, Guerrera S, Righetti PG. Electrically immobilized enzyme reactors: bioconversion of a charged substrate. Hydrolysis Of penicillin G by penicillin G acylase. Biotechnol Bioeng 1999; 64:383-91. [PMID: 10397877 DOI: 10.1002/(sici)1097-0290(19990820)64:4<383::aid-bit1>3.0.co;2-h] [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: 11/11/2022]
Abstract
The possibility of using the multicompartment immobilized enzyme reactor (MIER) in presence of a charged substrate is here explored. Penicillin G acylase is used to convert penicillin G (a free acid, with a pK of 2.6) into two charged products: phenyl acetic acid (PAA, with a pK of 4.2) and 6-aminopenicillanic acid (6-APA, a zwitterion with a pI of 3.6). The enzyme is trapped by an isoelectric mechanism in a chamber of the electrolyzer delimited by a pI 5.0 and a pI 9.0 amphoteric, isoelectric membranes. Under normal operating conditions (continuous substrate feeding in the presence of an electric field), only a low substrate conversion can be achieved, due to rapid electrophoretic transport of unreacted penicillin G out of the reaction chamber towards the anode. Excellent conversion rates (>96%) are obtained under a "doubly-discontinuous" operation mode: a time-lapse substrate feeding, accompanied by short times (4-8 min) of electric field interruption. The product of interest (6-APA, a precursor of semisynthetic penicillins), by virtue of its amphoteric nature, is trapped in a chamber delimited by a pI 3.5 membrane and a pI 5.5 membrane, adjacent to the reaction chamber on its anodic side. The other contaminant product (PAA) first accumulates in the same chamber and then progressively vacates it to collect in the anodic reservoir, leaving behind a pure 6-APA solution. In this operation mode, vanishing amounts of unreacted substrate (penicillin G) leave the reaction chamber to contaminate the adjacent, anodic chambers. A novel class of zwitterionic buffers is additionally reported, able to cover very thoroughly any pH value along the pH 3-10 interval: polymeric, zwitterionic buffers, synthesized with the principle of the Immobiline (acrylamido weak acids and bases) chemicals. Enhanced enzyme reactivity is found in this macromolecular buffers as compared to conventional ones.
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Affiliation(s)
- A Bossi
- University of Verona, Department of Industrial and Agricultural Biotechnologies, Strada Le Grazie, Ca' Vignal, 37134 Verona, Italy.
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