1
|
Gurung MK, Altermark B, Helland R, Smalås AO, Ræder ILU. Features and structure of a cold active N-acetylneuraminate lyase. PLoS One 2019; 14:e0217713. [PMID: 31185017 PMCID: PMC6559660 DOI: 10.1371/journal.pone.0217713] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 05/16/2019] [Indexed: 11/23/2022] Open
Abstract
N-acetylneuraminate lyases (NALs) are enzymes that catalyze the reversible cleavage and synthesis of sialic acids. They are therefore commonly used for the production of these high-value sugars. This study presents the recombinant production, together with biochemical and structural data, of the NAL from the psychrophilic bacterium Aliivibrio salmonicida LFI1238 (AsNAL). Our characterization shows that AsNAL possesses high activity and stability at alkaline pH. We confirm that these properties allow for the use in a one-pot reaction at alkaline pH for the synthesis of N-acetylneuraminic acid (Neu5Ac, the most common sialic acid) from the inexpensive precursor N-acetylglucosamine. We also show that the enzyme has a cold active nature with an optimum temperature for Neu5Ac synthesis at 20°C. The equilibrium constant for the reaction was calculated at different temperatures, and the formation of Neu5Ac acid is favored at low temperatures, making the cold active enzyme a well-suited candidate for use in such exothermic reactions. The specific activity is high compared to the homologue from Escherichia coli at three tested temperatures, and the enzyme shows a higher catalytic efficiency and turnover number for cleavage at 37°C. Mutational studies reveal that amino acid residue Asn 168 is important for the high kcat. The crystal structure of AsNAL was solved to 1.65 Å resolution and reveals a compact, tetrameric protein similar to other NAL structures. The data presented provides a framework to guide further optimization of its application in sialic acid production and opens the possibility for further design of the enzyme.
Collapse
Affiliation(s)
- Man Kumari Gurung
- The Norwegian Structural Biology Center (NorStruct), Department of Chemistry, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Bjørn Altermark
- The Norwegian Structural Biology Center (NorStruct), Department of Chemistry, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Ronny Helland
- The Norwegian Structural Biology Center (NorStruct), Department of Chemistry, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Arne O. Smalås
- The Norwegian Structural Biology Center (NorStruct), Department of Chemistry, UiT- The Arctic University of Norway, Tromsø, Norway
| | - Inger Lin U. Ræder
- The Norwegian Structural Biology Center (NorStruct), Department of Chemistry, UiT- The Arctic University of Norway, Tromsø, Norway
- * E-mail:
| |
Collapse
|
2
|
Chen X, Zhou J, Zhang L, Pu Z, Liu L, Shen W, Fan Y. Development of an Escherichia coli-based biocatalytic system for the efficient synthesis of N-acetyl-D-neuraminic acid. Metab Eng 2018; 47:374-382. [DOI: 10.1016/j.ymben.2018.04.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 04/12/2018] [Accepted: 04/15/2018] [Indexed: 11/29/2022]
|
3
|
Molecular Characterization of a Novel N-Acetylneuraminate Lyase from a Deep-Sea Symbiotic Mycoplasma. Mar Drugs 2018; 16:md16030080. [PMID: 29510563 PMCID: PMC5867624 DOI: 10.3390/md16030080] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 02/19/2018] [Accepted: 02/26/2018] [Indexed: 12/01/2022] Open
Abstract
N-acetylneuraminic acid (Neu5Ac) based novel pharmaceutical agents and diagnostic reagents are highly required in medical fields. However, N-acetylneuraminate lyase(NAL)for Neu5Ac synthesis is not applicable for industry due to its low catalytic efficiency. In this study, we biochemically characterized a deep-sea NAL enzyme (abbreviated form: MyNal) from a symbiotic Mycoplasma inhabiting the stomach of a deep-sea isopod, Bathynomus jamesi. Enzyme kinetic studies of MyNal showed that it exhibited a very low Km for both cleavage and synthesis activities compared to previously described NALs. Though it favors the cleavage process, MyNal out-competes the known NALs with respect to the efficiency of Neu5Ac synthesis and exhibits the highest kcat/Km values. High expression levels of recombinant MyNal could be achieved (9.56 mol L−1 culture) with a stable activity in a wide pH (5.0–9.0) and temperature (40–60 °C) range. All these features indicated that the deep-sea NAL has potential in the industrial production of Neu5Ac. Furthermore, we found that the amino acid 189 of MyNal (equivalent to Phe190 in Escherichia coli NAL), located in the sugar-binding domain, GX189DE, was also involved in conferring its enzymatic features. Therefore, the results of this study improved our understanding of the NALs from different environments and provided a model for protein engineering of NAL for biosynthesis of Neu5Ac.
Collapse
|
4
|
A sialic acid aldolase from Peptoclostridium difficile NAP08 with 4-hydroxy-2-oxo-pentanoate aldolase activity. Enzyme Microb Technol 2016; 92:99-106. [DOI: 10.1016/j.enzmictec.2016.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/28/2016] [Accepted: 07/08/2016] [Indexed: 11/15/2022]
|
5
|
Abstract
Sialic acids, or the more broad term nonulosonic acids, comprise a family of nine-carbon keto-sugars ubiquitous on mammalian mucous membranes as terminal modifications of mucin glycoproteins. Sialic acids have a limited distribution among bacteria, and the ability to catabolize sialic acids is mainly confined to pathogenic and commensal species. This ability to utilize sialic acid as a carbon source is correlated with bacterial virulence, especially, in the sialic acid rich environment of the oral cavity, respiratory, intestinal, and urogenital tracts. This chapter discusses the distribution of sialic acid catabolizers among the sequenced bacterial genomes and examines the studies that have linked sialic acid catabolism with increased in vivo fitness in a number of species using several animal models. This chapter presents the most recent findings in sialobiology with a focus on sialic acid catabolism, which demonstrates an important relationship between the catabolism of sialic acid and bacterial pathogenesis.
Collapse
|
6
|
Ji W, Sun W, Feng J, Song T, Zhang D, Ouyang P, Gu Z, Xie J. Characterization of a novel N-acetylneuraminic acid lyase favoring industrial N-acetylneuraminic acid synthesis. Sci Rep 2015; 5:9341. [PMID: 25799411 PMCID: PMC5380162 DOI: 10.1038/srep09341] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 02/26/2015] [Indexed: 01/22/2023] Open
Abstract
N-Acetylneuraminic acid lyase (NAL, E.C. number 4.1.3.3) is a Class I aldolase that catalyzes the reversible aldol cleavage of N-acetylneuraminic acid (Neu5Ac) from pyruvate and N-acetyl-D-mannosamine (ManNAc). Due to the equilibrium favoring Neu5Ac cleavage, the enzyme catalyzes the rate-limiting step of two biocatalytic reactions producing Neu5Ac in industry. We report the biochemical characterization of a novel NAL from a “GRAS” (General recognized as safe) strain C. glutamicum ATCC 13032 (CgNal). Compared to all previously reported NALs, CgNal exhibited the lowest kcat/Km value for Neu5Ac and highest kcat/Km values for ManNAc and pyruvate, which makes CgNal favor Neu5Ac synthesis the most. The recombinant CgNal reached the highest expression level (480 mg/L culture), and the highest reported yield of Neu5Ac was achieved (194 g/L, 0.63 M). All these unique properties make CgNal a promising biocatalyst for industrial Neu5Ac biosynthesis. Additionally, although showing the best Neu5Ac synthesis activity among the NAL family, CgNal is more related to dihydrodipicolinate synthase (DHDPS) by phylogenetic analysis. The activities of CgNal towards both NAL's and DHDPS' substrates are fairly high, which indicates CgNal a bi-functional enzyme. The sequence analysis suggests that CgNal might have adopted a unique set of residues for substrates recognition.
Collapse
Affiliation(s)
- Wenyan Ji
- 1] State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing, PR China [2] College of Life Science and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, PR China [3] National Engineering Technique Research Center for Biotechnology, Nanjing, PR China
| | - Wujin Sun
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, United States
| | - Jinmei Feng
- Department of Pathogenic Biology, School of Medicine, Jianghan University, Wuhan, China
| | - Tianshun Song
- College of Life Science and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, PR China
| | - Dalu Zhang
- International Cooperation Division, China National Center for Biotechnology Development, Beijing, PR China
| | - Pingkai Ouyang
- 1] State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing, PR China [2] College of Life Science and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, PR China [3] National Engineering Technique Research Center for Biotechnology, Nanjing, PR China
| | - Zhen Gu
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, United States
| | - Jingjing Xie
- 1] State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing, PR China [2] College of Life Science and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, PR China [3] National Engineering Technique Research Center for Biotechnology, Nanjing, PR China
| |
Collapse
|
7
|
Vetting MW, Al-Obaidi N, Zhao S, San Francisco B, Kim J, Wichelecki DJ, Bouvier JT, Solbiati JO, Vu H, Zhang X, Rodionov DA, Love JD, Hillerich BS, Seidel RD, Quinn RJ, Osterman AL, Cronan JE, Jacobson MP, Gerlt JA, Almo SC. Experimental strategies for functional annotation and metabolism discovery: targeted screening of solute binding proteins and unbiased panning of metabolomes. Biochemistry 2015; 54:909-31. [PMID: 25540822 PMCID: PMC4310620 DOI: 10.1021/bi501388y] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
![]()
The
rate at which genome sequencing data is accruing demands enhanced
methods for functional annotation and metabolism discovery. Solute
binding proteins (SBPs) facilitate the transport of the first reactant
in a metabolic pathway, thereby constraining the regions of chemical
space and the chemistries that must be considered for pathway reconstruction.
We describe high-throughput protein production and differential scanning
fluorimetry platforms, which enabled the screening of 158 SBPs against
a 189 component library specifically tailored for this class of proteins.
Like all screening efforts, this approach is limited by the practical
constraints imposed by construction of the library, i.e., we can study
only those metabolites that are known to exist and which can be made
in sufficient quantities for experimentation. To move beyond these
inherent limitations, we illustrate the promise of crystallographic-
and mass spectrometric-based approaches for the unbiased use of entire
metabolomes as screening libraries. Together, our approaches identified
40 new SBP ligands, generated experiment-based annotations for 2084
SBPs in 71 isofunctional clusters, and defined numerous metabolic
pathways, including novel catabolic pathways for the utilization of
ethanolamine as sole nitrogen source and the use of d-Ala-d-Ala as sole carbon source. These efforts begin to define an
integrated strategy for realizing the full value of amassing genome
sequence data.
Collapse
Affiliation(s)
- Matthew W Vetting
- Department of Biochemistry, Albert Einstein College of Medicine , Bronx, New York 10461, United States
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Metabolism of sialic acid by Bifidobacterium breve UCC2003. Appl Environ Microbiol 2014; 80:4414-26. [PMID: 24814790 DOI: 10.1128/aem.01114-14] [Citation(s) in RCA: 107] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Bifidobacteria constitute a specific group of commensal bacteria that inhabit the gastrointestinal tracts of humans and other mammals. Bifidobacterium breve UCC2003 has previously been shown to utilize several plant-derived carbohydrates that include cellodextrins, starch, and galactan. In the present study, we investigated the ability of this strain to utilize the mucin- and human milk oligosaccharide (HMO)-derived carbohydrate sialic acid. Using a combination of transcriptomic and functional genomic approaches, we identified a gene cluster dedicated to the uptake and metabolism of sialic acid. Furthermore, we demonstrate that B. breve UCC2003 can cross feed on sialic acid derived from the metabolism of 3'-sialyllactose, an abundant HMO, by another infant gut bifidobacterial strain, Bifidobacterium bifidum PRL2010.
Collapse
|
9
|
|
10
|
Molecular characterization of a novel N-acetylneuraminate lyase from Lactobacillus plantarum WCFS1. Appl Environ Microbiol 2011; 77:2471-8. [PMID: 21317263 DOI: 10.1128/aem.02927-10] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
N-Acetylneuraminate lyases (NALs) or sialic acid aldolases catalyze the reversible aldol cleavage of N-acetylneuraminic acid (Neu5Ac) to form pyruvate and N-acetyl-d-mannosamine (ManNAc). In nature, N-acetylneuraminate lyase occurs mainly in pathogens. However, this paper describes how an N-acetylneuraminate lyase was cloned from the human gut commensal Lactobacillus plantarum WCFS1 (LpNAL), overexpressed, purified, and characterized for the first time. This novel enzyme, which reaches a high expression level (215 mg liter(-1) culture), shows similar catalytic efficiency to the best NALs previously described. This homotetrameric enzyme (132 kDa) also shows high stability and activity at alkaline pH (pH > 9) and good temperature stability (60 to 70°C), this last feature being further improved by the presence of stabilizing additives. These characteristics make LpNAL a promising biocatalyst. When its sequence was compared with that of other, related (real and putative) NALs described in the databases, it was seen that NAL enzymes could be divided into four structural groups and three subgroups. The relation of these subgroups with human and other mammalian NALs is also discussed.
Collapse
|
11
|
Pasteurella multocida sialic acid aldolase: a promising biocatalyst. Appl Microbiol Biotechnol 2008; 79:963-70. [PMID: 18521592 DOI: 10.1007/s00253-008-1506-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2008] [Revised: 04/06/2008] [Accepted: 04/14/2008] [Indexed: 10/22/2022]
Abstract
Sialic acid aldolases or N-acetylneuraminate lyases (NanAs) catalyze the reversible aldol cleavage of N-acetylneuraminic acid (Neu5Ac) to form pyruvate and N-acetyl-D: -mannosamine (ManNAc). A capillary electrophoresis assay was developed to directly characterize the activities of NanAs in both Neu5Ac cleavage and Neu5Ac synthesis directions. The assay was used to obtain the pH profile and the kinetic data of a NanA cloned from Pasteurella multocida P-1059 (PmNanA) and a previously reported recombinant Escherichia coli K12 NanA (EcNanA). Both enzymes are active in a broad pH range of 6.0-9.0 in both reaction directions and have similar kinetic parameters. Substrates specificity studies showed that 5-O-methyl-ManNAc, a ManNAc derivative, can be used efficiently as a substrate by PmNanA, but not efficiently by EcNanA, for the synthesis of 8-O-methyl Neu5Ac. In addition, PmNanA (250 mg l(-1) culture) has a higher expression level (2.5-fold) than EcNanA (94 mg l(-1) culture). The higher expression level and a broader substrate tolerance make PmNanA a better catalyst than EcNanA for the chemoenzymatic synthesis of sialic acids and their derivatives.
Collapse
|
12
|
Xu P, Qiu JH, Zhang YN, Chen J, Wang PG, Yan B, Song J, Xi RM, Deng ZX, Ma CQ. Efficient Whole-Cell Biocatalytic Synthesis ofN-Acetyl-D-neuraminic Acid. Adv Synth Catal 2007. [DOI: 10.1002/adsc.200700094] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
13
|
Zhang J, Wu B, Zhang Y, Kowal P, Wang PG. Creatine phosphate--creatine kinase in enzymatic synthesis of glycoconjugates. Org Lett 2003; 5:2583-6. [PMID: 12868864 DOI: 10.1021/ol034319a] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
[reaction: see text] Enzymatic production of glycoconjugates is hampered by expensive phosphagens such as acetyl phosphate (AcP) and phosphoenolpyruvate (PEP). Here, we introduce creatine phosphate--creatine kinase system as a novel and practical energy source in carbohydrate synthesis. This system was successfully demonstrated in the production of bioactive oligosaccharides with different sugar nucleotide regeneration systems.
Collapse
Affiliation(s)
- Jianbo Zhang
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA
| | | | | | | | | |
Collapse
|
14
|
Krüger D, Schauer R, Traving C. Characterization and mutagenesis of the recombinant N-acetylneuraminate lyase from Clostridium perfringens: insights into the reaction mechanism. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:3831-9. [PMID: 11432751 DOI: 10.1046/j.1432-1327.2001.02297.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The N-acetylneuraminate lyase from Clostridium perfringens was expressed in Escherichia coli as a fusion protein with a His-tag and purified to homogeneity using metal chelate affinity and anion exchange chromatography. The purified enzyme has a pH optimum of 7.6 and a temperature optimum of 65-70 degrees C. In kinetic studies the lyase exhibits a Km of 3.2 mM for Neu5Ac and a Vmax of 27.5 U x mg(-1). To clarify the functional role of some putative active site residues, site-directed mutagenesis was performed. Lysine 161 was identified as the residue forming the Schiff base intermediate with the substrate. Tyrosine 133 was shown to be also a catalytically important residue; it seems to function as an acceptor for the proton of the C4 hydroxyl group, as already suggested by other groups. Furthermore, it is involved in stabilizing the Schiff base intermediate. Mutations of aspartate 187 and glutamate 188 indicate that both residues are involved in substrate binding. In this respect the carboxy group of aspartate 187 seems to be particularly important. Based on the results of these studies, a model of the reaction mechanism is discussed.
Collapse
Affiliation(s)
- D Krüger
- Biochemisches Institut, Christian-Albrechts-Universität, Kiel, Germany
| | | | | |
Collapse
|
15
|
Barbosa JA, Smith BJ, DeGori R, Ooi HC, Marcuccio SM, Campi EM, Jackson WR, Brossmer R, Sommer M, Lawrence MC. Active site modulation in the N-acetylneuraminate lyase sub-family as revealed by the structure of the inhibitor-complexed Haemophilus influenzae enzyme. J Mol Biol 2000; 303:405-21. [PMID: 11031117 DOI: 10.1006/jmbi.2000.4138] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The N-acetylneuraminate lyase (NAL) sub-family of (beta/alpha)(8) enzymes share a common catalytic step but catalyse reactions in different biological pathways. Known examples include NAL, dihydrodipicolinate synthetase (DHDPS), d-5-keto-4-deoxyglucarate dehydratase, 2-keto-3-deoxygluconate aldolase, trans-o-hydroxybenzylidenepyruvate hydrolase-aldolase and trans-2'-carboxybenzalpyruvate hydratase-aldolase. Little is known about the way in which the three-dimensional structure of the respective active sites are modulated across the sub-family to achieve cognate substrate recognition. We present here the structure of Haemophilus influenzae NAL determined by X-ray crystallography to a maximum resolution of 1.60 A, in native form and in complex with three substrate analogues (sialic acid alditol, 4-deoxy-sialic acid and 4-oxo-sialic acid). These structures reveal for the first time the mode of binding of the complete substrate in the NAL active site. On the basis of the above structures, that of substrate-complexed DHDPS and sequence comparison across the sub-family we are able to propose a unified model for active site modulation. The model is one of economy, allowing wherever appropriate the retention or relocation of residues associated with binding common substrate substituent groups. Our structures also suggest a role for the strictly conserved tyrosine residue found in all active sites of the sub-family, namely that it mediates proton abstraction by the alpha-keto acid carboxylate in a substrate-assisted catalytic reaction pathway.
Collapse
Affiliation(s)
- J A Barbosa
- Biomolecular Research Institute, 343 Royal Parade, Parkville, Victoria, Australia
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Vimr E, Lichtensteiger C, Steenbergen S. Sialic acid metabolism's dual function in Haemophilus influenzae. Mol Microbiol 2000; 36:1113-23. [PMID: 10844695 DOI: 10.1046/j.1365-2958.2000.01925.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Many bacterial commensals and pathogens use the sialic acids as carbon and nitrogen sources. In Escherichia coli, the breakdown of these sugars is catalysed by gene products of the nan (Nacylneuraminate) operon; other microorganisms may use a similar catabolic strategy. Despite the known ligand and antirecognition functions of the sialic acids, the contribution of their catabolism to infection or host colonization has never been directly investigated. We addressed these questions with Haemophilus influenzae type b, which metabolizes relatively few carbohydrates, using the infant-rat infection model. The predicted H. influenzae homologue (HI0142) of the E. coli sialic acid aldolase structural gene, nanA, was subcloned and mutagenized by insertion of a kanamycin resistance cassette. Phenotypic investigation of the resulting H. influenzae aldolase mutants showed that: (i) HI0142 is essential for sialic acid degradation; (ii) the products of the open reading frames (ORFs) flanking HI0142 (HI0140, 41, 44 and 45) are likely to have the same functions as those of their counterparts in E. coli; (iii) sialylation of the lipooligosaccharide (LOS) epitope recognized by monoclonal antibody 3F11 is dependent on an environmental source of sialic acid; (iv) a nanA mutant hypersialylates its LOS sialyl acceptor, corresponding to an apparent increased fitness of the mutant in the infant-rat model; and (v) expression of the LOS sialyl acceptor is altered in cells grown without exogenous sialic acid, indicating the direct or indirect effect of sialic acid metabolism on LOS antigenicity. Taken together the data show the dual role of sialic acid catabolism in nutrition and cell surface modulation.
Collapse
Affiliation(s)
- E Vimr
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61802, USA.
| | | | | |
Collapse
|