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Chi MC, Lu BY, Huang YF, Wang SW, Lin MG, Wang TF. Effects of Sodium Dodecyl Sulfate on the Enzyme Catalysis and Conformation of a Recombinant γ-Glutamyltranspeptidase from Bacillus licheniformis. Protein J 2023; 42:64-77. [PMID: 36739340 DOI: 10.1007/s10930-023-10095-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/30/2023] [Indexed: 02/06/2023]
Abstract
The study of interactions between proteins and surfactants is of relevance in a diverse range of applications including food, enzymatic detergent formulation, and drug delivery. In spite of sodium dodecyl sulfate (SDS)-induced unfolding has been studied in detail at the protein level, deciphering the conformation-activity relationship of a recombinant γ-glutamyltranspeptidase (BlrGGT) from Bacillus licheniformis remains important to understand how the transpeptidase activity is related to its conformation. In this study, we examined the enzyme catalysis and conformational transition of BlrGGT in the presence of SDS. Enzymatic assays showed that the transpeptidase activity of BlrGGT was greatly affected by SDS in a concentration-dependent manner with approximately 90% inactivation at 6 mM. Native polyacrylamide gel electrophoresis of SDS-treated samples clearly revealed that the heterodimeric enzyme was apparently dissociated into two different subunits at concentrations above 2 mM. The study of enzyme kinetics showed that SDS can act as a mixed-type inhibitor to reduce the catalytic efficiency of BlrGGT. Moreover, the t1/2 value of the enzyme at 55 °C was greatly reduced from 495.1 min to 7.4 min in the presence of 1 mM SDS. The I3/I1 ratio of pyrene excimer fluorescence emission changed around 3.7 mM SDS in the absence of BlrGGT and the inflection point of enzyme samples was reduced to less than 2.7 mM. The Far-UV CD spectrum of the native enzyme had two negative peaks at 208 and 222 nm, respectively; however, both negative peaks increased in magnitude with increasing SDS concentration and reached maximal values at above 4.0 mM. The intrinsic fluorescence spectra of tryptophan further demonstrated that the SDS-induced enzyme conformational transition occurred at approximately 5.1 mM. Tween 20 significantly suppressed the interaction of BlrGGT with SDS by forming mixed micelles at a molar ratio of 1.0. Taken together, this study definitely promotes our better understanding of the relationship between the conformation and catalysis of BlrGGT.
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Affiliation(s)
- Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Bo-Yuan Lu
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Yu-Fen Huang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Shih-Wei Wang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Min-Guan Lin
- Institute of Molecular Biology, Academia Sinica, Nangang District, Taipei City, 11529, Taiwan
| | - Tzu-Fan Wang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan.
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2
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Robescu M, Annunziata F, Somma V, Calvio C, Morelli CF, Speranza G, Tamborini L, Ubiali D, Pinto A, Bavaro T. From Batch to Continuous Flow Bioprocessing: Use of an Immobilized γ-Glutamyl Transferase from B. subtilis for the Synthesis of Biologically Active Peptide Derivatives. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:13692-13699. [PMID: 36149987 PMCID: PMC9614966 DOI: 10.1021/acs.jafc.2c03702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
γ-Glutamyl-peptides are frequently endowed with biological activities. In this work, "kokumi peptides" such as γ-glutamyl-methionine (1) and γ-glutamyl-(S)-allyl-cysteine (2), as well as the neuroprotective γ-glutamyl-taurine (3) and the antioxidant ophthalmic acid (4), were synthesized through an enzymatic transpeptidation reaction catalyzed by the γ-glutamyl transferase from Bacillus subtilis (BsGGT) using glutamine as the γ-glutamyl donor. BsGGT was covalently immobilized on glyoxyl-agarose resulting in high protein immobilization yield and activity recovery (>95%). Compounds 1-4 were obtained in moderate yields (19-40%, 5-10 g/L) with a variable purity depending on the presence of the main byproduct (γ-glutamyl-glutamine, 0-16%). To achieve process intensification and better control of side reactions, the synthesis of 2 was moved from batch to continuous flow. The specific productivity was 1.5 times higher than that in batch synthesis (13.7 μmol/min*g), but it was not accompanied by a paralleled improvement of the impurity profile.
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Affiliation(s)
- Marina
S. Robescu
- Department
of Drug Sciences, University of Pavia, viale Taramelli 12, Pavia 27100, Italy
| | - Francesca Annunziata
- Department
of Pharmaceutical Sciences, University of
Milano, via Mangiagalli 25, Milano 20122, Italy
| | - Valeria Somma
- Department
of Chemistry, University of Milano, via Golgi 19, Milano 20122, Italy
| | - Cinzia Calvio
- Department
of Biology and Biotechnology “L. Spallanzani”, University of Pavia, via Ferrata 1, Pavia 27100, Italy
| | - Carlo F. Morelli
- Department
of Chemistry, University of Milano, via Golgi 19, Milano 20122, Italy
| | - Giovanna Speranza
- Department
of Chemistry, University of Milano, via Golgi 19, Milano 20122, Italy
| | - Lucia Tamborini
- Department
of Pharmaceutical Sciences, University of
Milano, via Mangiagalli 25, Milano 20122, Italy
| | - Daniela Ubiali
- Department
of Drug Sciences, University of Pavia, viale Taramelli 12, Pavia 27100, Italy
| | - Andrea Pinto
- Department
of Food, Environmental and Nutritional Sciences, University of Milano, via Celoria 2, Milano 20133, Italy
| | - Teodora Bavaro
- Department
of Drug Sciences, University of Pavia, viale Taramelli 12, Pavia 27100, Italy
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3
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Lin LL, Lu BY, Chi MC, Huang YF, Lin MG, Wang TF. Activation and thermal stabilization of a recombinant γ-glutamyltranspeptidase from Bacillus licheniformis ATCC 27811 by monovalent cations. Appl Microbiol Biotechnol 2022; 106:1991-2006. [PMID: 35230495 DOI: 10.1007/s00253-022-11836-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 02/08/2022] [Accepted: 02/12/2022] [Indexed: 12/27/2022]
Abstract
The regulation of enzyme activity through complexation with certain metal ions plays an important role in many biological processes. In addition to divalent metals, monovalent cations (MVCs) frequently function as promoters for efficient biocatalysis. Here, we examined the effect of MVCs on the enzymatic catalysis of a recombinant γ-glutamyltranspeptidase (BlrGGT) from Bacillus licheniformis ATCC 27,811 and the application of a metal-activated enzyme to L-theanine synthesis. The transpeptidase activity of BlrGGT was enhanced by Cs+ and Na+ over a broad range of concentrations with a maximum of 200 mM. The activation was essentially independent of the ionic radius, but K+ contributed the least to enhancing the catalytic efficiency. The secondary structure of BlrGGT remained mostly unchanged in the presence of different concentrations of MVCs, but there was a significant change in its tertiary structure under the same conditions. Compared with the control, the half-life (t1/2) of the Cs+-enriched enzyme at 60 and 65 °C was shown to increase from 16.3 and 4.0 min to 74.5 and 14.3 min, respectively. The simultaneous addition of Cs+ and Mg2+ ions exerted a synergistic effect on the activation of BlrGGT. This was adequately reflected by an improvement in the conversion of substrates to L-theanine by 3.3-15.1% upon the addition of 200 mM MgCl2 into a reaction mixture comprising the freshly desalted enzyme (25 μg/mL), 250 mM L-glutamine, 600 mM ethylamine, 200 mM each of the MVCs, and 50 mM borate buffer (pH 10.5). Taken together, our results provide interesting insights into the complexation of MVCs with BlrGGT and can therefore be potentially useful to the biocatalytic production of naturally occurring γ-glutamyl compounds. KEY POINTS: • The transpeptidase activity of B. licheniformis γ-glutamyltranspeptidase can be activated by monovalent cations. • The thermal stability of the enzyme was profoundly increased in the presence of 200 mM Cs+. • The simultaneous addition of Cs+and Mg2+ions to the reaction mixture improves L-theanine production.
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Affiliation(s)
- Long-Liu Lin
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Bo-Yuan Lu
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Yu-Fen Huang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Min-Guan Lin
- Institute of Molecular Biology, Academia Sinica, Nangang District, Taipei City, 11529, Taiwan
| | - Tzu-Fan Wang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan.
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4
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The Use of a Thermal Process to Produce Black Garlic: Differences in the Physicochemical and Sensory Characteristics Using Seven Varieties of Fresh Garlic. Foods 2021; 10:foods10112703. [PMID: 34828984 PMCID: PMC8623035 DOI: 10.3390/foods10112703] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 11/02/2021] [Accepted: 11/03/2021] [Indexed: 01/01/2023] Open
Abstract
Black garlic (BG) is a product originating from fresh garlic (FG) and substantially differs in many aspects from FG due to the process called ageing. During this thermal process, the health-promoting properties of FG are enhanced, and the sensory traits are altered. However, very little is known about how the physicochemical properties of different FG varieties affect these properties of BG. Thus, the aim of this study was to investigate the influence of seven FG varieties subjected to the thermal process on the physicochemical parameters of BG. To prepare the BG samples, a fifteen-day ageing process involving a temperature gradient ranging from 30 to 82 °C was used. It was found that the antioxidant activity, the total polyphenol content, and the total soluble solids increased during ageing, while the pH level, moisture content, and lightness decreased in all the garlic varieties. The varieties of garlic differed in the studied traits significantly, both before (FG) and after ageing (BG). In the sensory analysis, significant differences between the BG varieties were observed only in the pleasantness of texture, while the remaining sensory descriptors (pleasantness of color, odor, taste and intensity of the garlic aroma, and overall acceptability) were not affected by variety. The correlations suggest that most of the FG’s studied parameters in this study do not correlate with the properties of BG and cannot be used for the prediction of the quality of BG. Additionally, HPLC-MS/MS analysis revealed substantial changes in the composition of low molecular compounds.
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Somma V, Calvio C, Rabuffetti M, Rama E, Speranza G, Morelli CF. An overall framework for the E. coli γ-glutamyltransferase-catalyzed transpeptidation reactions. Bioorg Chem 2021; 115:105217. [PMID: 34364051 DOI: 10.1016/j.bioorg.2021.105217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 07/16/2021] [Accepted: 07/24/2021] [Indexed: 10/20/2022]
Abstract
γ-Glutamyl derivatives of proteinogenic or modified amino acids raise considerable interest as flavor enhancers or biologically active compounds. However, their supply, on a large scale and at reasonable costs, remains challenging. Enzymatic synthesis has been recognized as a possible affordable alternative with respect to both isolation procedures from natural sources, burdened by low-yield and by the requirement of massive amount of starting material, and chemical synthesis, inconvenient because of the need of protection/deprotection steps. The E. coli γ-glutamyltransferase (Ec-GGT) has already been proposed as a biocatalyst for the synthesis of various γ-glutamyl derivatives. However, enzymatic syntheses using this enzyme usually provide the desired products in limited yield. Hydrolysis and autotranspeptidation of the donor substrate have been identified as the side reactions affecting the final yield of the catalytic process. In addition, experimental conditions need to be specifically adjusted for each acceptor substrate. Substrate specificity and the fine characterization of the activities exerted by the enzyme over time has so far escaped rationalization. In this work, reactions catalyzed by Ec-GGT between the γ-glutamyl donor glutamine and several representative acceptor amino acids have been finely analyzed with the identification of single reaction products over time. This approach allowed to rationalize the effect of donor/acceptor molar ratio on the outcome of the transpeptidation reaction and on the distribution of the different byproducts, inferring a general scheme for Ec-GGT-catalyzed reactions. The propensity to react of the different acceptor substrates is in agreement with recent findings obtained using model substrates and further supported by x-ray crystallography and will contribute to characterize the still elusive acceptor binding site of the enzyme.
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Affiliation(s)
- Valeria Somma
- Department of Chemistry, Università degli Studi di Milano, via Golgi, 19, 20133 Milano, Italy.
| | - Cinzia Calvio
- Department of Biology and Biotechnology, Università degli Studi di Pavia, via Ferrata, 9, 27100 Pavia, Italy.
| | - Marco Rabuffetti
- Department of Chemistry, Università degli Studi di Milano, via Golgi, 19, 20133 Milano, Italy.
| | - Erlinda Rama
- Department of Biology and Biotechnology, Università degli Studi di Pavia, via Ferrata, 9, 27100 Pavia, Italy.
| | - Giovanna Speranza
- Department of Chemistry, Università degli Studi di Milano, via Golgi, 19, 20133 Milano, Italy.
| | - Carlo F Morelli
- Department of Chemistry, Università degli Studi di Milano, via Golgi, 19, 20133 Milano, Italy.
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6
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Saini M, Kashyap A, Bindal S, Saini K, Gupta R. Bacterial Gamma-Glutamyl Transpeptidase, an Emerging Biocatalyst: Insights Into Structure-Function Relationship and Its Biotechnological Applications. Front Microbiol 2021; 12:641251. [PMID: 33897647 PMCID: PMC8062742 DOI: 10.3389/fmicb.2021.641251] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 02/15/2021] [Indexed: 12/16/2022] Open
Abstract
Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a variety of roles in diverse organisms. Higher eukaryotes mainly utilize GGT for glutathione degradation, and mammalian GGTs have implications in many physiological disorders also. GGTs from unicellular prokaryotes serve different physiological functions in Gram-positive and Gram-negative bacteria. In the present review, the physiological significance of bacterial GGTs has been discussed categorizing GGTs from Gram-negative bacteria like Escherichia coli as glutathione degraders and from pathogenic species like Helicobacter pylori as virulence factors. Gram-positive bacilli, however, are considered separately as poly-γ-glutamic acid (PGA) degraders. The structure-function relationship of the GGT is also discussed mainly focusing on the crystallization of bacterial GGTs along with functional characterization of conserved regions by site-directed mutagenesis that unravels molecular aspects of autoprocessing and catalysis. Only a few crystal structures have been deciphered so far. Further, different reports on heterologous expression of bacterial GGTs in E. coli and Bacillus subtilis as hosts have been presented in a table pointing toward the lack of fermentation studies for large-scale production. Physicochemical properties of bacterial GGTs have also been described, followed by a detailed discussion on various applications of bacterial GGTs in different biotechnological sectors. This review emphasizes the potential of bacterial GGTs as an industrial biocatalyst relevant to the current switch toward green chemistry.
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Affiliation(s)
| | | | | | | | - Rani Gupta
- Department of Microbiology, University of Delhi South Campus, New Delhi, India
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7
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Magnetic Cross-Linked Enzyme Aggregates of a Transpeptidase-Specialized Variant (N450D) of Bacillus licheniformis γ-Glutamyl Transpeptidase: An Efficient and Stable Biocatalyst for l-Theanine Synthesis. Catalysts 2021. [DOI: 10.3390/catal11020243] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
γ-Glutamyl transpeptidase (GGT) catalyzes the transfer of glutathione’s γ-glutamyl group and related γ-glutamyl amides to water, amino acids or peptides, and utilizes a conserved Thr residue to process its own polypeptide chain into a large and a small subunit that then assemble to produce a catalytically competent enzyme. In this study, the magnetic cross-linked enzyme aggregates (mCLEAs) of a transpeptidase-specialized variant (N450D) of Bacillus licheniformis GGT were successfully prepared with optimized process parameters viz.1.25:1 (v/v) of isopropanol to N450D (0.3 mg/mL) ratio/0.02:1 (w/w) of enzyme to 3-aminopropyl triethoxysilane (APTES)-coated magnetic nanoparticle ratio/20 mM of glutaraldehyde. The prepared magnetic nanoparticles and immobilized enzyme (N450D-mCLEAs) were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscope integrated with energy dispersive X-ray spectroscopy (FESEM/EDS), and superparamagnetic analysis. As compared with free enzyme, N450D-mCLEAs displayed significantly higher heat resistance at temperatures of 55 and 60 °C, and had a greater stability over a storage period of one month. The immobilized enzyme could also be reused for 10 consecutive biocatalytic cycles with no significant reduction in the percent yield of l-theanine. Conclusively, this immobilization strategy surely provides a meaningful glance of developing N450D-mediated biocatalysis for the production of physiologically important γ-glutamyl compounds.
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8
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Enzymatic synthesis of L-theanine from L-glutamine and ethylamine by Bacillus licheniformis γ-glutamyltranspeptidase and its mutants specialized in transpeptidase activity. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2019. [DOI: 10.1016/j.bcab.2019.101393] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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9
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Mutational Analysis of a Highly Conserved PLSSMXP Sequence in the Small Subunit of Bacillus licheniformis γ-Glutamyltranspeptidase. Biomolecules 2019; 9:biom9090508. [PMID: 31546955 PMCID: PMC6769717 DOI: 10.3390/biom9090508] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 01/13/2023] Open
Abstract
A highly conserved 458PLSSMXP464 sequence in the small subunit (S-subunit) of an industrially important Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) was identified by sequence alignment. Molecular structures of the precursor mimic and the mature form of BlGGT clearly reveal that this peptide sequence is in close spatial proximity to the self-processing and catalytic sites of the enzyme. To probe the role of this conserved sequence, ten mutant enzymes of BlGGT were created through a series of deletion and alanine-scanning mutagenesis. SDS-PAGE and densitometric analyses showed that the intrinsic ability of BlGGT to undergo autocatalytic processing was detrimentally affected by the deletion-associated mutations. However, loss of self-activating capacity was not obviously observed in most of the Ala-replacement mutants. The Ala-replacement mutants had a specific activity comparable to or greater than that of the wild-type enzyme; conversely, all deletion mutants completely lost their enzymatic activity. As compared with BlGGT, S460A and S461S showed greatly enhanced kcat/Km values by 2.73- and 2.67-fold, respectively. The intrinsic tryptophan fluorescence and circular dichroism spectral profiles of Ala-replacement and deletion mutants were typically similar to those of BlGGT. However, heat and guanidine hydrochloride-induced unfolding transitions of the deletion-associated mutant proteins were severely reduced as compared with the wild-type enzyme. The predictive mutant models suggest that the microenvironments required for both self-activation and catalytic reaction of BlGGT can be altered upon mutations.
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10
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Massone M, Calvio C, Rabuffetti M, Speranza G, Morelli CF. Effect of the inserted active-site-covering lid loop on the catalytic activity of a mutant B. subtilis γ-glutamyltransferase (GGT). RSC Adv 2019; 9:34699-34709. [PMID: 35530678 PMCID: PMC9073855 DOI: 10.1039/c9ra05941e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 10/11/2019] [Indexed: 11/24/2022] Open
Abstract
γ-Glutamylpeptides are compounds derived from the acylation of an amino acid or a short peptide by the γ-carboxyl carbon of the side chain of glutamic acid. Due to their altered chemico-physical and organoleptic properties, they may be interesting substitutes or precursors of parent compounds used in pharmaceutical, dietetic and cosmetic formulations. Some of them are naturally occurring flavor enhancers or are endowed with biological activities. Enzymatic approaches to the synthesis of γ-glutamyl derivatives based on the use of γ-glutamyltransferases (GGTs, EC 2.3.2.2) have been proposed, which should be able to alleviate the problems connected with the troublesome and low-yielding extraction from natural sources or the non-economical chemical synthesis, which requires protection/deprotection steps. With the aim of overcoming the current limitations in the use of GGTs as biocatalysts, a mutant GGT was investigated. The mutant GGT was obtained by inserting the active-site-covering lid loop of the E. coli GGT onto the structure of B. subtilis GGT. With respect to the wild-type enzyme, the mutant showed a more demanding substrate specificity and a low hydrolase activity. These results represent an attempt to correlate the structural features of a GGT to its different activities. However, the ability of the mutant enzyme to catalyze the subsequent addition of several γ-glutamyl units, inherited by the parent B. subtilis GGT, still represents a limitation to its full application as a biocatalyst for preparative purposes. A mutant γ-glutamyltransferase with improve transpeptidase activity was obtained by inserting the active site-covering lid loop on an enzyme naturally lacking it.![]()
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Affiliation(s)
- Michela Massone
- Department of Chemistry
- Università degli Studi di Milano
- 20133 Milano
- Italy
| | - Cinzia Calvio
- Department of Biology and Biotechnology
- Università degli Studi di Pavia
- 27100 Pavia
- Italy
| | - Marco Rabuffetti
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l’Ambiente
- Università degli Studi di Milano
- 20133 Milano
- Italy
| | - Giovanna Speranza
- Department of Chemistry
- Università degli Studi di Milano
- 20133 Milano
- Italy
- Istituto di Scienze e Tecnologie Molecolari (INSTM)
| | - Carlo F. Morelli
- Department of Chemistry
- Università degli Studi di Milano
- 20133 Milano
- Italy
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11
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Facile immobilization of Bacillus licheniformis γ-glutamyltranspeptidase onto graphene oxide nanosheets and its application to the biocatalytic synthesis of γ-l-glutamyl peptides. Int J Biol Macromol 2018; 117:1326-1333. [DOI: 10.1016/j.ijbiomac.2017.11.153] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 10/27/2017] [Accepted: 11/25/2017] [Indexed: 02/04/2023]
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