1
|
Sheng H, Jing Y, An N, Shen X, Sun X, Yan Y, Wang J, Yuan Q. Extending the shikimate pathway for microbial production of maleate from glycerol in engineered Escherichia coli. Biotechnol Bioeng 2021; 118:1840-1850. [PMID: 33512000 DOI: 10.1002/bit.27700] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 01/19/2021] [Accepted: 01/23/2021] [Indexed: 11/12/2022]
Abstract
Maleate is one of the most important unsaturated four-carbon dicarboxylic acids. It serves as an attractive building block in cosmetic, polymer, and pharmaceutical industries. Currently, industrial production of maleate relies mainly on chemical synthesis using benzene or butane as the starting materials under high temperature, which suffers from strict reaction conditions and low product yield. Here, we propose a novel biosynthetic pathway for maleate production in engineered Escherichia coli. We screened a superior salicylate 5-hydroxylase that can catalyze hydroxylation of salicylate into gentisate with high conversion rate. Then, introduction of salicylate biosynthetic pathway and gentisate ring cleavage pathway allowed the synthesis of maleate from glycerol. Further optimizations including enhancement of precursors supply, disruption of competing pathways, and construction of a pyruvate recycling system, boosted maleate titer to 2.4 ± 0.1 g/L in shake flask experiments. Subsequent scale-up biosynthesis of maleate in a 3-L bioreactor under fed-batch culture conditions enabled the production of 14.5 g/L of maleate, indicating a 268-fold improvement compared with the titer generated by the wildtype E. coli strain carrying the entire maleate biosynthetic pathway. This study provided a promising microbial platform for industrial level synthesis of maleate, and demonstrated the highest titer of maleate production in microorganisms so far.
Collapse
Affiliation(s)
- Huakang Sheng
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| | - Yijie Jing
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| | - Ning An
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| | - Xiaolin Shen
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| | - Xinxiao Sun
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| | - Yajun Yan
- College of Engineering, The University of Georgia, Athens, Georgia, USA
| | - Jia Wang
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| | - Qipeng Yuan
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing, China
| |
Collapse
|
2
|
Li N, Peng Q, Yao L, He Q, Qiu J, Cao H, He J, Niu Q, Lu Y, Hui F. Roles of the Gentisate 1,2-Dioxygenases DsmD and GtdA in the Catabolism of the Herbicide Dicamba in Rhizorhabdus dicambivorans Ndbn-20. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:9287-9298. [PMID: 32786824 DOI: 10.1021/acs.jafc.0c01523] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
3-Chlorogentisate is a key intermediate in the catabolism of the herbicide dicamba in R. dicambivorans Ndbn-20. In this study, we identified two gentisate 1,2-dioxygenases (GDOs), DsmD and GtdA, from Ndbn-20. The amino acid sequence similarity between DsmD and GtdA is 51%. Both of them are dimers and showed activities to gentisate and 3-chlorogentisate but not 3,6-dichlorogentisate (3,6-DCGA) or 6-chlorogentisate in vitro. The kcat/Km of DsmD for 3-chlorogentisate was 28.7 times higher than that of GtdA, whereas the kcat/Km of DsmD for gentisate was only one-fourth of that of GtdA. Transcription of dsmD was dramatically induced by 3-chlorogentisate but not gentisate, whereas gtdA was not induced. Disruption of dsmD resulted in a significant decline in the degradation rates of 3-chlorogentisate and dicamba but had no effect on the degradation of gentisate, whereas the result of disruption of gtdA was converse; the disruption of both dsmD and gtdA led to the inability to degrade 3-chlorogentisate and gentisate. This study revealed that 3-chlorogentisate but not gentisate or 3,6-DCGA is the ring-cleavage substrate in the dicamba degradation pathway in R. dicambivorans Ndbn-20; DsmD is specifically responsible for cleavage of 3-chlorogentisate, whereas GtdA is a general GDO involved in the catabolism of various natural aromatic compounds.
Collapse
Affiliation(s)
- Na Li
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
| | - Qian Peng
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Li Yao
- School of Marine and Biological Engineering, Yancheng Teachers University, Yancheng, Jiangsu 224002, China
| | - Qin He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Jiguo Qiu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Hui Cao
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China
| | - Qiuhong Niu
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
| | - Yunfeng Lu
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
- State Key Laboratory of Motor Vehicle Biofuel Technology, Nanyang, Henan 473000, China
| | - Fengli Hui
- School of Life Science and Technology, Nanyang Normal University, Nanyang, Henan 473061, China
| |
Collapse
|
3
|
Hong H, Seo H, Park W, Kim KJ. Sequence, structure and function-based classification of the broadly conserved FAH superfamily reveals two distinct fumarylpyruvate hydrolase subfamilies. Environ Microbiol 2019; 22:270-285. [PMID: 31657110 DOI: 10.1111/1462-2920.14844] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 10/21/2019] [Accepted: 10/23/2019] [Indexed: 11/30/2022]
Abstract
Fumarylacetoacetate hydrolase (FAH) superfamily proteins are found ubiquitously in microbial pathways involved in the catabolism of aromatic substances. Although extensive bioinformatic data on these proteins have been acquired, confusion caused by problems with the annotation of these proteins hinders research into determining their physiological functions. Here we classify 606 FAH superfamily proteins using a maximum likelihood (ML) phylogenetic tree, comparative gene-neighbourhood patterns and in vitro enzyme assays. The FAH superfamily proteins used for the analyses are divided into five distinct subfamilies, and two of them, FPH-A and FPH-B, contain the majority of the proteins of undefined function. These subfamilies include clusters designated FPH-I and FPH-II, respectively, which include two distinct types of fumarylpyruvate hydrolase (FPH), an enzyme involved in the final step of the gentisate pathway. We determined the crystal structures of these FPH enzymes at 2.0 Å resolutions and investigate the substrate binding mode by which these types of enzymes can accommodate fumarylpyruvate as a substrate. Consequentially, we identify the molecular signatures of the two types of FPH enzymes among the broadly conserved FAH superfamily proteins. Our studies allowed us to predict the relationship of unknown FAH superfamily proteins using their sequence information.
Collapse
Affiliation(s)
- Hwaseok Hong
- Structural and Molecular Biology Laboratory, School of Life Sciences, KNU Creative BioResearch Group, Kyungpook National University, Daegu, 702701, Republic of Korea.,KNU Institute for Microorganisms, Kyungpook National University, Daegu, 702701, Republic of Korea
| | - Hogyun Seo
- Structural and Molecular Biology Laboratory, School of Life Sciences, KNU Creative BioResearch Group, Kyungpook National University, Daegu, 702701, Republic of Korea.,KNU Institute for Microorganisms, Kyungpook National University, Daegu, 702701, Republic of Korea
| | - Woojin Park
- Structural and Molecular Biology Laboratory, School of Life Sciences, KNU Creative BioResearch Group, Kyungpook National University, Daegu, 702701, Republic of Korea.,KNU Institute for Microorganisms, Kyungpook National University, Daegu, 702701, Republic of Korea
| | - Kyung-Jin Kim
- Structural and Molecular Biology Laboratory, School of Life Sciences, KNU Creative BioResearch Group, Kyungpook National University, Daegu, 702701, Republic of Korea.,KNU Institute for Microorganisms, Kyungpook National University, Daegu, 702701, Republic of Korea
| |
Collapse
|
4
|
Hong H, Seo H, Kim KJ. Structural insights into a maleylpyruvate hydrolase from sphingobium sp. SYK-6, a bacterium degrading lignin-derived aryls. Biochem Biophys Res Commun 2019; 514:765-771. [DOI: 10.1016/j.bbrc.2019.05.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 05/03/2019] [Indexed: 11/25/2022]
|
5
|
Roles of Two Glutathione-Dependent 3,6-Dichlorogentisate Dehalogenases in Rhizorhabdus dicambivorans Ndbn-20 in the Catabolism of the Herbicide Dicamba. Appl Environ Microbiol 2018; 84:AEM.00623-18. [PMID: 29934333 DOI: 10.1128/aem.00623-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 06/18/2018] [Indexed: 11/20/2022] Open
Abstract
The herbicide dicamba is initially demethylated to 3,6-dichlorosalicylate (3,6-DCSA) in Rhizorhabdus dicambivorans Ndbn-20 and is subsequently 5-hydroxylated to 3,6-dichlorogentisate (3,6-DCGA). In the present study, two glutathione-dependent 3,6-DCGA dehalogenases, DsmH1 and DsmH2, were identified in strain Ndbn-20. DsmH2 shared a low identity (only 31%) with the tetrachlorohydroquinone (TCHQ) dehalogenase PcpC from Sphingobium chlorophenolicum ATCC 39723, while DsmH1 shared a high identity (79%) with PcpC. In the phylogenetic tree of related glutathione S-transferases (GSTs), DsmH1 and DsmH2, together with PcpC and the 2,5-dichlorohydroquinone dehalogenase LinD, formed a separate clade. DsmH1 and DsmH2 were synthesized in Escherichia coli BL21 and purified as His-tagged enzymes. Both enzymes required glutathione (GSH) as a cofactor and could 6-dechlorinate 3,6-DCGA to 3-chlorogentisate in vitro DsmH2 had a significantly higher catalytic efficiency toward 3,6-DCGA than DsmH1. Transcription and disruption analysis revealed that DsmH2 but not DsmH1 was responsible for the 6-dechlorination of 3,6-DCGA in strain Ndbn-20 in vivo Furthermore, we propose a novel eta class of GSTs to accommodate the four bacterial dehalogenases PcpC, LinD, DsmH1, and DsmH2.IMPORTANCE Dicamba is an important herbicide, and its use and leakage into the environment have dramatically increased since the large-scale planting of genetically modified (GM) dicamba-resistant crops in 2015. However, the complete catabolic pathway of dicamba has remained unknown, which limits ecotoxicological studies of this herbicide. Our previous study revealed that 3,6-DCGA was an intermediate of dicamba degradation in strain Ndbn-20. In this study, we identified two glutathione-dependent 3,6-DCGA dehalogenases, DsmH1 and DsmH2, and demonstrated that DsmH2 is physiologically responsible for the 6-dechlorination of 3,6-DCGA in strain Ndbn-20. GSTs play an important role in the detoxification and degradation of a variety of endogenous and exogenous toxic compounds. On the basis of their sequence identities, phylogenetic status, and functions, the four bacterial GSH-dependent dehalogenases (PcpC, LinD, DsmH1, and DsmH2) were reclassified as a new eta class of GSTs. This study helps us to elucidate the microbial catabolism of dicamba and enhances our understanding of the diversity and functions of GSTs.
Collapse
|
6
|
Li N, Yao L, He Q, Qiu J, Cheng D, Ding D, Tao Q, He J, Jiang J. 3,6-Dichlorosalicylate Catabolism Is Initiated by the DsmABC Cytochrome P450 Monooxygenase System in Rhizorhabdus dicambivorans Ndbn-20. Appl Environ Microbiol 2018; 84:e02133-17. [PMID: 29196293 PMCID: PMC5795090 DOI: 10.1128/aem.02133-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Accepted: 11/28/2017] [Indexed: 11/20/2022] Open
Abstract
The degradation of the herbicide dicamba is initiated by demethylation to form 3,6-dichlorosalicylate (3,6-DCSA) in Rhizorhabdusdicambivorans Ndbn-20. In the present study, a 3,6-DCSA degradation-deficient mutant, Ndbn-20m, was screened. A cluster, dsmR1DABCEFGR2, was lost in this mutant. The cluster consisted of nine genes, all of which were apparently induced by 3,6-DCSA. DsmA shared 30 to 36% identity with the monooxygenase components of reported three-component cytochrome P450 systems and formed a monophyletic branch in the phylogenetic tree. DsmB and DsmC were most closely related to the reported [2Fe-2S] ferredoxin and ferredoxin reductase, respectively. The disruption of dsmA in strain Ndbn-20 resulted in inactive 3,6-DCSA degradation. When dsmABC, but not dsmA alone, was introduced into mutant Ndbn-20m and Sphingobium quisquiliarum DC-2 (which is unable to degrade salicylate and its derivatives), they acquired the ability to hydroxylate 3,6-DCSA. Single-crystal X-ray diffraction demonstrated that the DsmABC-catalyzed hydroxylation occurred at the C-5 position of 3,6-DCSA, generating 3,6-dichlorogentisate (3,6-DCGA). In addition, DsmD shared 51% identity with GtdA (a gentisate and 3,6-DCGA 1,2-dioxygenase) from Sphingomonas sp. strain RW5. However, unlike GtdA, the purified DsmD catalyzed the cleavage of gentisate and 3-chlorogentisate but not 6-chlorogentisate or 3,6-DCGA in vitro Based on the bioinformatic analysis and gene function studies, a possible catabolic pathway of dicamba in R. dicambivorans Ndbn-20 was proposed.IMPORTANCE Dicamba is widely used to control a variety of broadleaf weeds and is a promising target herbicide for the engineering of herbicide-resistant crops. The catabolism of dicamba has thus received increasing attention. Bacteria mineralize dicamba initially via demethylation, generating 3,6-dichlorosalicylate. However, the catabolism of 3,6-dichlorosalicylate remains unknown. In this study, we cloned a gene cluster, dsmR1DABCEFGR2, involved in 3,6-dichlorosalicylate degradation from R. dicambivorans Ndbn-20, demonstrated that the cytochrome P450 monooxygenase system DsmABC was responsible for the 5-hydroxylation of 3,6-dichlorosalicylate, and proposed a dicamba catabolic pathway. This study provides a basis to elucidate the catabolism of dicamba and has benefits for the ecotoxicological study of dicamba. Furthermore, the hydroxylation of salicylate has been previously reported to be catalyzed by single-component flavoprotein or three-component Rieske non-heme iron oxygenase, whereas DsmABC was the only cytochrome P450 monooxygenase system hydroxylating salicylate and its methyl- or chloro-substituted derivatives.
Collapse
Affiliation(s)
- Na Li
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Li Yao
- School of Marine and Biological Engineering, Yancheng Teachers University, Yancheng, Jiangsu, China
| | - Qin He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Jiguo Qiu
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Dan Cheng
- Laboratory Centre of Life Science, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Derong Ding
- Beijing DBN Biotech Co., Ltd., Beijing, China
| | - Qing Tao
- Beijing DBN Biotech Co., Ltd., Beijing, China
| | - Jian He
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
- Laboratory Centre of Life Science, College of Life Science, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Jiandong Jiang
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, Jiangsu, China
| |
Collapse
|
7
|
Engineering a synthetic pathway for maleate in Escherichia coli. Nat Commun 2017; 8:1153. [PMID: 29074856 PMCID: PMC5658364 DOI: 10.1038/s41467-017-01233-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 08/31/2017] [Indexed: 12/31/2022] Open
Abstract
Maleate is one of the most important dicarboxylic acids and is used to produce various polymer compounds and pharmaceuticals. Herein, microbial production of maleate is successfully achieved, to our knowledge for the first time, using genetically modified Escherichia coli. A synthetic pathway of maleate is constructed in E. coli by combining the polyketide biosynthesis pathway and benzene ring cleavage pathway. The metabolic engineering approach used to fine-tune the synthetic pathway drastically improves maleate production and demonstrates that one of the rate limiting steps exists in the conversion of chorismate to gentisate. In a batch culture of the optimised transformant, grown in a 1-L jar fermentor, the amount of produced maleate reaches 7.1 g L-1, and the yield is 0.221 mol mol-1. Our results suggest that the construction of synthetic pathways by combining a secondary metabolite pathway and the benzene ring cleavage pathway is a powerful tool for producing various valuable chemicals.
Collapse
|
8
|
Degradation of Diphenyl Ether in Sphingobium phenoxybenzoativorans SC_3 Is Initiated by a Novel Ring Cleavage Dioxygenase. Appl Environ Microbiol 2017; 83:AEM.00104-17. [PMID: 28283519 DOI: 10.1128/aem.00104-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 02/19/2017] [Indexed: 11/20/2022] Open
Abstract
Sphingobium phenoxybenzoativorans SC_3 degrades and utilizes diphenyl ether (DE) or 2-carboxy-DE as its sole carbon and energy source. In this study, we report the degradation of DE and 2-carboxy-DE initiated by a novel ring cleavage angular dioxygenase (diphenyl ether dioxygenase [Dpe]) in the strain. Dpe functions at the angular carbon and its adjacent carbon (C-1a, C-2) of a benzene ring in DE (or the 2-carboxybenzene ring in 2-carboxy-DE) and cleaves the C-1a-C-2 bond (decarboxylation occurs simultaneously for 2-carboxy-DE), yielding 2,4-hexadienal phenyl ester, which is subsequently hydrolyzed to muconic acid semialdehyde and phenol. Dpe is a type IV Rieske non-heme iron oxygenase (RHO) and consists of three components: a hetero-oligomer oxygenase, a [2Fe-2S]-type ferredoxin, and a glutathione reductase (GR)-type reductase. Genetic analyses revealed that dpeA1A2 plays an essential role in the degradation and utilization of DE and 2-carboxy-DE in S. phenoxybenzoativorans SC_3. Enzymatic study showed that transformation of 1 molecule of DE needs two molecules of oxygen and two molecules of NADH, supporting the assumption that the cleavage of DE catalyzed by Dpe is a continuous two-step dioxygenation process: DE is dioxygenated at C-1a and C-2 to form a hemiacetal-like intermediate, which is further deoxygenated, resulting in the cleavage of the C-1a-C-2 bond to form one molecule of 2,4-hexadienal phenyl ester and two molecules of H2O. This study extends our knowledge of the mode and mechanism of ring cleavage of aromatic compounds.IMPORTANCE Benzene ring cleavage, catalyzed by dioxygenase, is the key and speed-limiting step in the aerobic degradation of aromatic compounds. As previously reported, in the ring cleavage of DEs, the benzene ring needs to be first dihydroxylated at a lateral position and subsequently dehydrogenated and opened through extradiol cleavage. This process requires three enzymes (two dioxygenases and one dehydrogenase). In this study, we identified a novel angular dioxygenase (Dpe) in S. phenoxybenzoativorans SC_3. Under Dpe-mediated catalysis, the benzene ring of DE is dioxygenated at the angular position (C-1a, C-2), resulting in the cleavage of the C-1a-C-2 bond to generate a novel product, 2,4-hexadienal phenyl ester. This process needs only one angular dioxygenase, Dpe. Thus, the ring cleavage catalyzed by Dpe represents a novel mechanism of benzene ring cleavage.
Collapse
|
9
|
Identification of a Specific Maleate Hydratase in the Direct Hydrolysis Route of the Gentisate Pathway. Appl Environ Microbiol 2015; 81:5753-60. [PMID: 26070679 DOI: 10.1128/aem.00975-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/09/2015] [Indexed: 11/20/2022] Open
Abstract
In contrast to the well-characterized and more common maleylpyruvate isomerization route of the gentisate pathway, the direct hydrolysis route occurs rarely and remains unsolved. In Pseudomonas alcaligenes NCIMB 9867, two gene clusters, xln and hbz, were previously proposed to be involved in gentisate catabolism, and HbzF was characterized as a maleylpyruvate hydrolase converting maleylpyruvate to maleate and pyruvate. However, the complete degradation pathway of gentisate through direct hydrolysis has not been characterized. In this study, we obtained from the NCIMB culture collection a Pseudomonas alcaligenes spontaneous mutant strain that lacked the xln cluster and designated the mutant strain SponMu. The hbz cluster in strain SponMu was resequenced, revealing the correct location of the stop codon for hbzI and identifying a new gene, hbzG. HbzIJ was demonstrated to be a maleate hydratase consisting of large and small subunits, stoichiometrically converting maleate to enantiomerically pure d-malate. HbzG is a glutathione-dependent maleylpyruvate isomerase, indicating the possible presence of two alternative pathways of maleylpyruvate catabolism. However, the hbzF-disrupted mutant could still grow on gentisate, while disruption of hbzG prevented this ability, indicating that the direct hydrolysis route was not a complete pathway in strain SponMu. Subsequently, a d-malate dehydrogenase gene was introduced into the hbzG-disrupted mutant, and the engineered strain was able to grow on gentisate via the direct hydrolysis route. This fills a gap in our understanding of the direct hydrolysis route of the gentisate pathway and provides an explanation for the high yield of d-malate from maleate by this d-malate dehydrogenase-deficient natural mutant.
Collapse
|
10
|
Involvement of the global regulator GlxR in 3-hydroxybenzoate and gentisate utilization by Corynebacterium glutamicum. Appl Environ Microbiol 2014; 80:4215-25. [PMID: 24795375 DOI: 10.1128/aem.00290-14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium glutamicum is an industrially important producer of amino acids and organic acids, as well as an emerging model system for aromatic assimilation. An IclR-type regulator GenR has been characterized to activate the transcription of genDFM and genKH operons for 3-hydroxybenzoate and gentisate catabolism and represses its own expression. On the other hand, GlxR, a global regulator of the cyclic AMP (cAMP) receptor protein-fumarate nitrate reductase regulator (CRP-FNR) type, was also predicted to be involved in this pathway. In this study, electrophoretic mobility shift assays and footprinting analyses demonstrated that GlxR bound to three sites in the promoter regions of three gen operons. A combination of site-directed mutagenesis of the biding sites, promoter activity assay, and GlxR overexpression demonstrated that GlxR repressed their expression by binding these sites. One GlxR binding site (DFMx) was found to be located -13 to +8 bp upstream of the genDFM promoter, which was involved in negative regulation of genDFM transcription. The GlxR binding site R-KHx01 (located between positions -11 to +5) was upstream of the genKH promoter sequence and involved in negative regulation of its transcription. The binding site R-KHx02, at which GlxR binds to genR promoter to repress its expression, was found within a footprint extending from positions -71 to -91 bp. These results reveal that GlxR represses the transcription of all three gen operons and then contributes to the synchronization of their expression for 3-hydroxybenzoate and gentisate catabolism in collaboration with the specific regulator GenR.
Collapse
|