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Wang X, Hatta S, Matsui D, Imamura H, Wakayama M. Expression and characterization of C-terminal truncated mutants of γ-glutamyltranspeptidase II (PaGGTII) from Pseudomonas aeruginosa PAO1. Protein Expr Purif 2023:106321. [PMID: 37315656 DOI: 10.1016/j.pep.2023.106321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 06/09/2023] [Accepted: 06/11/2023] [Indexed: 06/16/2023]
Abstract
The gene encoding γ-glutamyltranspeptidase II (PaGGTII) from Pseudomonas aeruginosa PAO1 was cloned in Escherichia coli. Recombinant PaGGTII showed a weak activity (0.0332 U/mg), and it can be easily inactivated. Multiple alignment of microbial GGTs showed the redundancy of the C-terminal of the small subunit of PaGGTII in length. The truncation of eight amino acid residues at the C-terminal of PaGGTII remarkably improved the activity and stability of the enzyme (PaGGTIIΔ8; 0.388 U/mg). Further truncation at the C-terminal also provided the enzyme relatively higher activity (PaGGTIIΔ9, -Δ10, -Δ11, and -Δ12). Among C-terminal truncated mutants, we focused on PaGGTIIΔ8 and examined the effect of C-terminal amino acid residues on the properties of PaGGTIIΔ8 because the activity of PaGGTII was found to be greatly improved when 8 amino acid residues were truncated. Various mutant enzymes with different C-terminal amino acid residues were constructed. They were expressed in E. coli and purified to homogeneity by ion-exchange chromatography. The properties of PaGGTIIΔ8 and the mutants obtained from mutation at E569 were characterized. Km and kcat of PaGGTIIΔ8 for γ-glutamyl-p-nitroanilide (γ-GpNA) were 8.05 mM and 15.49 s-1, respectively. PaGGTIIΔ8E569Y showed the highest catalytic efficiency for γ-GpNA with a kcat/Km of 12.55 mM-1 s-1. Mg2+, Ca2+, and Mn2+ exhibited positive effects on the catalytic activity for PaGGTIIΔ8 and its ten E569 mutants.
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Affiliation(s)
- Xinjia Wang
- College of Life Sciences, Ritsumeikan University, Nojihigashi 1-1-1, Kusatsu, Shiga, 525-8577, Japan
| | - Seiji Hatta
- College of Life Sciences, Ritsumeikan University, Nojihigashi 1-1-1, Kusatsu, Shiga, 525-8577, Japan
| | - Daisuke Matsui
- College of Life Sciences, Ritsumeikan University, Nojihigashi 1-1-1, Kusatsu, Shiga, 525-8577, Japan
| | - Hiroshi Imamura
- Department of Bio-Science, Nagahama Institute of Bio-Science and Technology, Tamuramachi 1266, Nagahama, Shiga, 526-0829, Japan
| | - Mamoru Wakayama
- College of Life Sciences, Ritsumeikan University, Nojihigashi 1-1-1, Kusatsu, Shiga, 525-8577, Japan.
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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: 28] [Impact Index Per Article: 9.3] [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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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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Site-directed mutagenesis of a conserved Asn450 residue of Bacillus licheniformis γ-glutamyltranspeptidase. Int J Biol Macromol 2016; 91:416-25. [DOI: 10.1016/j.ijbiomac.2016.05.101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 05/27/2016] [Accepted: 05/28/2016] [Indexed: 12/29/2022]
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Pica A, Chi MC, Chen YY, d'Ischia M, Lin LL, Merlino A. The maturation mechanism of γ-glutamyl transpeptidases: Insights from the crystal structure of a precursor mimic of the enzyme from Bacillus licheniformis and from site-directed mutagenesis studies. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1864:195-203. [PMID: 26536828 DOI: 10.1016/j.bbapap.2015.10.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 01/20/2023]
Abstract
γ-Glutamyl transpeptidases (γ-GTs) are members of N-terminal nucleophile hydrolase superfamily. They are synthetized as single-chain precursors, which are then cleaved to form mature enzymes. Basic aspects of autocatalytic processing of these pro-enzymes are still unknown. Here we describe the X-ray structure of the precursor mimic of Bacillus licheniformis γ-GT (BlGT), obtained by mutating catalytically important threonine to alanine (T399A-BlGT), and report results of autoprocessing of mutants of His401, Thr415, Thr417, Glu419 and Arg571. Data suggest that Thr417 is in a competent position to activate the catalytic threonine (Thr399) for nucleophilic attack of the scissile peptide bond and that Thr415 plays a major role in assisting the process. On the basis of these new structural results, a possible mechanism of autoprocessing is proposed. This mechanism, which guesses the existence of a six-membered transition state involving one carbonyl and two hydroxyl groups, is in agreement with all the available experimental data collected on γ-GTs from different species and with our new Ala-scanning mutagenesis data.
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Affiliation(s)
- Andrea Pica
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, Naples I-80126, Italy; Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone, 16, Naples 80133, Italy
| | - Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan
| | - Yi-Yu Chen
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan
| | - Marco d'Ischia
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, Naples I-80126, Italy
| | - Long-Liu Lin
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan
| | - Antonello Merlino
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia, Naples I-80126, Italy; Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone, 16, Naples 80133, Italy.
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6
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Lin LL, Chen YY, Chi MC, Merlino A. Low resolution X-ray structure of γ-glutamyltranspeptidase from Bacillus licheniformis: Opened active site cleft and a cluster of acid residues potentially involved in the recognition of a metal ion. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1523-9. [DOI: 10.1016/j.bbapap.2014.04.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 04/12/2014] [Accepted: 04/21/2014] [Indexed: 12/21/2022]
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Specific biochemical amniotic fluid pattern of fetal isolated esophageal atresia. Pediatr Res 2013; 74:601-5. [PMID: 23942557 DOI: 10.1038/pr.2013.131] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 02/10/2013] [Indexed: 11/08/2022]
Abstract
BACKGROUND Perinatal care of esophageal atresia (EA) may be improved by prenatal diagnosis. Ultrasound findings (polyhydramnios and/or nonvisualization of fetal stomach) lead to a detection rate of ~50%. An amniotic fluid (AF) biochemical pattern characterized by high total protein, γ-glutamyl transpeptidase (GGTP), and normal l-leucine-aminopeptidase (AMP) leads to a 100% detection rate. The aim of this study was to explain this specific pattern. METHODS On the basis of enzyme activities assay, the following four objectives were sought: (i) comparing AF markers between EA and other digestive tract atresias, (ii) determining local GGTP synthesis in the esophagus (immunohistobiochemistry), (iii) determining the presence of a specific AF-AMP activity inhibitor, and (iv) comparing AF-AMP and AF-GGTP half-lives. RESULTS The AF-EA pattern was similar to that observed in upper duodenal atresia (above the Oddi sphincter). No local synthesis of GGTP was observed in the esophagus. No AF-AMP activity inhibitor was found. AF-GGTP had a longer half-life than AF-AMP. CONCLUSION Due to the swallowing anomaly observed in EA, GGTP and AMP values physiologically observed at 18 wk will decrease on the basis of the half-lives of markers, with a flat slope for GGTP and a sharp slope for AMP, therefore explaining the differences observed in the AF-EA pattern.
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Chen YY, Tsai MG, Chi MC, Wang TF, Lin LL. Covalent Immobilization of Bacillus licheniformis γ-Glutamyl Transpeptidase on Aldehyde-Functionalized Magnetic Nanoparticles. Int J Mol Sci 2013; 14:4613-28. [PMID: 23443161 PMCID: PMC3634462 DOI: 10.3390/ijms14034613] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 02/20/2013] [Accepted: 02/21/2013] [Indexed: 11/16/2022] Open
Abstract
This work presents the synthesis and use of surface-modified iron oxide nanoparticles for the covalent immobilization of Bacillus licheniformis γ-glutamyl transpeptidase (BlGGT). Magnetic nanoparticles were prepared by an alkaline solution of divalent and trivalent iron ions, and they were subsequently treated with 3-aminopropyltriethoxysilane (APES) to obtain the aminosilane-coated nanoparticles. The functional group on the particle surface and the amino group of BlGGT was then cross-linked using glutaraldehyde as the coupling reagent. The loading capacity of the prepared nanoparticles for BlGGT was 34.2 mg/g support, corresponding to 52.4% recovery of the initial activity. Monographs of transmission electron microscopy revealed that the synthesized nanoparticles had a mean diameter of 15.1 ± 3.7 nm, and the covalent cross-linking of the enzyme did not significantly change their particle size. Fourier transform infrared spectroscopy confirmed the immobilization of BlGGT on the magnetic nanoparticles. The chemical and kinetic behaviors of immobilized BlGGT are mostly consistent with those of the free enzyme. The immobilized enzyme could be recycled ten times with 36.2% retention of the initial activity and had a comparable stability respective to free enzyme during the storage period of 30 days. Collectively, the straightforward synthesis of aldehyde-functionalized nanoparticles and the efficiency of enzyme immobilization offer wide perspectives for the practical use of surface-bound BlGGT.
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Affiliation(s)
- Yi-Yu Chen
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan; E-Mails: (Y.-Y.C.); (M.-G.T.); (M.-C.C.)
| | - Ming-Gen Tsai
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan; E-Mails: (Y.-Y.C.); (M.-G.T.); (M.-C.C.)
| | - Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan; E-Mails: (Y.-Y.C.); (M.-G.T.); (M.-C.C.)
| | - Tzu-Fan Wang
- Department of Life Sciences and Institute of Molecular Biology, National Chung Cheng University, Chiayi County 621, Taiwan
| | - Long-Liu Lin
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City 60004, Taiwan; E-Mails: (Y.-Y.C.); (M.-G.T.); (M.-C.C.)
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Castellano I, Merlino A. Gamma-Glutamyl Transpeptidases: Structure and Function. GAMMA-GLUTAMYL TRANSPEPTIDASES 2013. [DOI: 10.1007/978-3-0348-0682-4_1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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10
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Castellano I, Merlino A. γ-Glutamyltranspeptidases: sequence, structure, biochemical properties, and biotechnological applications. Cell Mol Life Sci 2012; 69:3381-94. [PMID: 22527720 PMCID: PMC11115026 DOI: 10.1007/s00018-012-0988-3] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 03/27/2012] [Accepted: 03/29/2012] [Indexed: 12/12/2022]
Abstract
γ-Glutamyltranspeptidases (γ-GTs) are ubiquitous enzymes that catalyze the hydrolysis of γ-glutamyl bonds in glutathione and glutamine and the transfer of the released γ-glutamyl group to amino acids or short peptides. These enzymes are involved in glutathione metabolism and play critical roles in antioxidant defense, detoxification, and inflammation processes. Moreover, γ-GTs have been recently found to be involved in many physiological disorders, such as Parkinson's disease and diabetes. In this review, the main biochemical and structural properties of γ-GTs isolated from different sources, as well as their conformational stability and mechanism of catalysis, are described and examined with the aim of contributing to the discussion on their structure-function relationships. Possible applications of γ-glutamyltranspeptidases in different fields of biotechnology and medicine are also discussed.
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Affiliation(s)
- Immacolata Castellano
- Institute of Protein Biochemistry, CNR, via Pietro Castellino 111, 80131 Naples, Italy
- Present Address: Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy
| | - Antonello Merlino
- Department of Chemical Sciences, University of Naples ‘Federico II’, Complesso Universitario di Monte Sant’Angelo, via cintia, 80126 Naples, Italy
- Institute of Biostructures and Bioimages, CNR, via Mezzocannone 16, 80100 Naples, Italy
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Chi MC, Chen YY, Lo HF, Lin LL. Experimental evidence for the involvement of amino acid residue Glu398 in the autocatalytic processing of Bacillus licheniformis γ-glutamyltranspeptidase. FEBS Open Bio 2012; 2:298-304. [PMID: 23772362 PMCID: PMC3678132 DOI: 10.1016/j.fob.2012.09.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 09/25/2012] [Accepted: 09/25/2012] [Indexed: 11/18/2022] Open
Abstract
The role of glutamate 398 in the autocatalytic processing of Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) was explored by site-directed mutagenesis. This glutamate was substituted by either alanine, aspartate, arginine or glutamine and the expressed mutant enzymes were purified to apparent homogeneity with metal-affinity chromatography. SDS–PAGE analysis showed that E398A, E398D and E398K were unable to process themselves into a large and a small subunit. However, E398Q was not only able to process itself, but also had a catalytic activity comparable to that of BlGGT. As compared with the wild-type enzyme, no significant change in circular dichroism spectra was observed for the mutant proteins. Thermal unfolding of BlGGT, E398A, E398D, E398K and E398Q followed the two-state unfolding process with a transition point (Tm) of 47.7–69.4 °C. Tryptophan fluorescence spectra of the mutant enzymes were different from the wild-type protein in terms of fluorescence intensity. Native BlGGT started to unfold beyond ∼1.92 M guanidine hydrochloride (GdnHCl) and reached an unfolded intermediate, [GdnHCl]0.5, N–U, at 3.07 M equivalent to free energy change (ΔGN−UH2O) of 14.53 kcal/mol for the N → U process, whereas the denaturation midpoints for the mutant enzymes were 1.31–2.99 M equivalent to ΔGN−UH2O of 3.29–12.05 kcal/mol. Taken together, these results strongly suggest that the explored glutamate residue is indeed important for the autocatalytic processing of BlGGT.
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Affiliation(s)
- Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, Taiwan
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12
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Enzymatic characterization of Bacillus licheniformis γ-glutamyltranspeptidase fused with N-terminally truncated forms of Bacillus sp. TS-23 α-amylase. Enzyme Microb Technol 2012; 51:86-94. [DOI: 10.1016/j.enzmictec.2012.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 04/18/2012] [Accepted: 04/21/2012] [Indexed: 11/17/2022]
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13
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Pica A, Russo Krauss I, Castellano I, Rossi M, La Cara F, Graziano G, Sica F, Merlino A. Exploring the unfolding mechanism of γ-glutamyltranspeptidases: the case of the thermophilic enzyme from Geobacillus thermodenitrificans. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2012; 1824:571-7. [PMID: 22322192 DOI: 10.1016/j.bbapap.2012.01.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 01/19/2012] [Accepted: 01/23/2012] [Indexed: 10/14/2022]
Abstract
γ-glutamyltranspeptidases (γ-GTs) are ubiquitous enzymes that catalyze the hydrolysis of γ-glutamyl bonds in glutathione and glutamine and the transfer of the released γ-glutamyl group to amino acids or short peptides. These enzymes are generally synthesized as precursor proteins, which undergo an intra-molecular autocatalytic cleavage yielding a large and a small subunit. In this study, circular dichroism and intrinsic fluorescence measurements have been used to investigate the structural features and the temperature- and guanidinium hydrochloride (GdnHCl)-induced unfolding of the mature form of the γ-GT from Geobacillus thermodenitrificans (GthGT) and that of its T353A mutant, which represents a mimic of the precursor protein. Data indicate that a) the mutant and the mature GthGT have a different secondary structure content and a slightly different exposure of hydrophobic regions, b) the thermal unfolding processes of both GthGT forms occur through a three-state model, characterized by a stable intermediate species, whereas chemical denaturations proceed through a single transition, c) both GthGT forms exhibit remarkable stability against temperature, but they do not display a strong resistance to the denaturing action of GdnHCl. These findings suggest that electrostatic interactions significantly contribute to the protein stability and that both the precursor and the mature form of GthGT assume compact and stable conformations to resist to the extreme temperatures where G. thermodenidrificans lives. Owing to its thermostability and unique catalytic properties, GthGT is an excellent candidate to be used as a glutaminase in food industry.
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Affiliation(s)
- Andrea Pica
- Department of Chemical Sciences, University of Naples, Naples, Italy
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Hung CP, Yang JC, Chen JH, Chi MC, Lin LL. Unfolding analysis of the mature and unprocessed forms of Bacillus licheniformis γ-glutamyltranspeptidase. J Biol Phys 2011; 37:463-75. [PMID: 22942488 DOI: 10.1007/s10867-011-9228-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Accepted: 05/08/2011] [Indexed: 11/30/2022] Open
Abstract
Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) undergoes an autocatalytic process to generate 44.9 and 21.7 kDa subunits; however, a mutant protein (T399A) loses completely the processing ability and mainly exists as a precursor. For a comprehensive understanding of their structural features, the biophysical properties of these two proteins were investigated by circular dichroism and fluorescence spectroscopy. Tryptophan fluorescence and circular dichroism spectra were nearly identical for BlGGT and T399A, but unfolding analyses revealed that these two proteins had a different sensitivity towards temperature- and guanidine hydrochloride (GdnHCl)-induced denaturation. BlGGT and the unprocessed T399A displayed T(m) values of 61.4°C and 68.1°C, respectively, and thermal unfolding of both proteins was found to be highly irreversible. Fluorescence quenching analysis showed that T399A had a dynamic quenching constant similar to that of the wild-type enzyme. BlGGT started to unfold beyond ∼2.14 M GdnHCl and reached an unfolded intermediate, [GdnHCl](0.5, N - U), at 2.85 M, corresponding to free energy change [Formula: see text] of 12.34 kcal mol( - 1), whereas the midpoint of the denaturation curve for T399A was approximately 3.94 M, corresponding to a [Formula: see text] of 4.45 kcal mol( - 1). Taken together, it can be concluded that the structural stability of BlGGT is superior to that of T399A.
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Biophysical Characterization of a Recombinant α-Amylase from Thermophilic Bacillus sp. strain TS-23. Protein J 2010; 29:572-82. [DOI: 10.1007/s10930-010-9287-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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