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Liew CY, Chen JL, Lin YT, Luo HS, Hung AT, Magoling BJA, Nguan HS, Lai CPK, Ni CK. Chromatograms and Mass Spectra of High-Mannose and Paucimannose N-Glycans for Rapid Isomeric Identifications. J Proteome Res 2024; 23:939-955. [PMID: 38364797 PMCID: PMC10913092 DOI: 10.1021/acs.jproteome.3c00640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 01/25/2024] [Accepted: 01/31/2024] [Indexed: 02/18/2024]
Abstract
N-Linked glycosylation is one of the most essential post-translational modifications of proteins. However, N-glycan structural determination remains challenging because of the small differences in structures between isomers. In this study, we constructed a database containing collision-induced dissociation MSn mass spectra and chromatograms of high-performance liquid chromatography for the rapid identification of high-mannose and paucimannose N-glycan isomers. These N-glycans include isomers by breaking of arbitrary numbers of glycosidic bonds at arbitrary positions of canonical Man9GlcNAc2 N-glycans. In addition, some GlcMannGlcNAc2 N-glycan isomers were included in the database. This database is particularly useful for the identification of the N-glycans not in conventional N-glycan standards. This study demonstrated the application of the database to structural assignment for high-mannose N-glycans extracted from bovine whey proteins, soybean proteins, human mammary epithelial cells, and human breast carcinoma cells. We found many N-glycans that are not expected to be generated by conventional biosynthetic pathways of multicellular eukaryotes.
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Affiliation(s)
- Chia Yen Liew
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
- International
Graduate Program of Molecular Science and Technology, National Taiwan University, Taipei 106216, Taiwan
- Molecular
Science and Technology, Taiwan International Graduate Program, Academia Sinica, Taipei 106216, Taiwan
| | - Jien-Lian Chen
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
| | - Yen-Ting Lin
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
| | - Hong-Sheng Luo
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
- Department
of Chemistry, National Taiwan Normal University, Taipei 116059, Taiwan
| | - An-Ti Hung
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
- Department
of Chemistry, National Tsing Hua University, Hsinchu 300044, Taiwan
| | - Bryan John Abel Magoling
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
- Institute
of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei 106216, Taiwan
- Chemical
Biology and Molecular Biophysics Program, Taiwan International Graduate
Program, Academia Sinica, Taipei 115201, Taiwan
| | - Hock-Seng Nguan
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
| | - Charles Pin-Kuang Lai
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
- Chemical
Biology and Molecular Biophysics Program, Taiwan International Graduate
Program, Academia Sinica, Taipei 115201, Taiwan
- Genome
and Systems Biology Degree Program, National
Taiwan University and Academia Sinica, Taipei 106216, Taiwan
| | - Chi-Kung Ni
- Institute
of Atomic and Molecular Sciences, Academia Sinica, Taipei 106216, Taiwan
- Molecular
Science and Technology, Taiwan International Graduate Program, Academia Sinica, Taipei 106216, Taiwan
- Department
of Chemistry, National Tsing Hua University, Hsinchu 300044, Taiwan
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2
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Liu Y, Yang T, Rong J, Yuan J, Man L, Wei M, Fan J, Lan Y, Liu Y, Gong G, Lu Y, Song X, Wang Z, Huang L. Integrated analysis of natural glycans using a versatile pyrazolone-type heterobifunctional tag ANPMP. Carbohydr Polym 2024; 327:121617. [PMID: 38171699 DOI: 10.1016/j.carbpol.2023.121617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 10/23/2023] [Accepted: 11/18/2023] [Indexed: 01/05/2024]
Abstract
Glycans mediate various biological processes through carbohydrate-protein interactions, and glycan microarrays have become indispensable tools for understanding these mechanisms. However, advances in functional glycomics are hindered by the absence of convenient and universal methods for obtaining natural glycan libraries with diverse structures from glycoconjugates. To address this challenge, we have developed an integrative approach that enables one-pot release and simultaneously capture, separation, structural characterization, and functional analysis of N/O-glycans. Using this approach, glycoconjugates are incubated with a pyrazolone-type heterobifunctional tag-ANPMP to obtain glycan-2ANPMP conjugates, which are then converted to glycan-AEPMP conjugates. We prepared a tagged glycan library from porcine gastric mucin, soy protein, human milk oligosaccharides, etc. Following derivatization by N-acetylation and permethylation, glycans were subjected to detailed structural characterization by ESI-MSn analysis, which revealed >83 highly pure glycan-AEPMPs containing various natural glycan epitopes. A shotgun microarray is constructed to study the fine details of glycan-bindings by proteins and antisera.
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Affiliation(s)
- Yuxia Liu
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Tong Yang
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Jinqiao Rong
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Jinhang Yuan
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Lijuan Man
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Ming Wei
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Jiangbo Fan
- Department of Obstetrics & Gynecology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, PR China
| | - Yao Lan
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Yinchuan Liu
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Guiping Gong
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Yu Lu
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China
| | - Xuezheng Song
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, United States
| | - Zhongfu Wang
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China.
| | - Linjuan Huang
- Key Laboratory of Glycobiology and Glycoengineering of Xi'an, College of Food Science and Technology, Northwest University, Xi'an, Shaanxi 710069, PR China.
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3
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Hu ZF, Zhong K, Cao H. Recent advances in enzymatic and chemoenzymatic synthesis of N- and O-glycans. Curr Opin Chem Biol 2024; 78:102417. [PMID: 38141531 DOI: 10.1016/j.cbpa.2023.102417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 11/28/2023] [Accepted: 11/30/2023] [Indexed: 12/25/2023]
Abstract
Glycosylation is one of the most common post-translational modifications of proteins, which plays essential roles in regulating the biological functions of proteins. Efficient and versatile methods for the synthesis of homogeneous and well-defined N- and O-glycans remain an urgent need for biological studies and biomedical applications. Despite their structural complexity, tremendous progress has been made in the synthesis of N- and O-glycans in recent years. This review discusses some recent advances in the enzymatic and chemoenzymatic synthesis of N- and O-glycans.
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Affiliation(s)
- Zhi-Fei Hu
- Key Laboratory of Marine Drugs of Ministry of Education, Shandong Key Laboratory of Glycoscience and Glycotechnology, School of Medicine and Pharmacy, Ocean University of China, Qingdao, Shandong, 266003, China; Laboratory for Marine Drugs and Bioproducts, Laoshan Laboratory, Qingdao, Shandong, 266237, China
| | - Kan Zhong
- Key Laboratory of Marine Drugs of Ministry of Education, Shandong Key Laboratory of Glycoscience and Glycotechnology, School of Medicine and Pharmacy, Ocean University of China, Qingdao, Shandong, 266003, China; Laboratory for Marine Drugs and Bioproducts, Laoshan Laboratory, Qingdao, Shandong, 266237, China
| | - Hongzhi Cao
- Key Laboratory of Marine Drugs of Ministry of Education, Shandong Key Laboratory of Glycoscience and Glycotechnology, School of Medicine and Pharmacy, Ocean University of China, Qingdao, Shandong, 266003, China; Laboratory for Marine Drugs and Bioproducts, Laoshan Laboratory, Qingdao, Shandong, 266237, China.
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4
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Helm J, Grünwald-Gruber C, Urteil J, Pabst M, Altmann F. Simple Routes to Stable Isotope-Coded Native Glycans. Anal Chem 2024; 96:163-169. [PMID: 38153380 PMCID: PMC10782419 DOI: 10.1021/acs.analchem.3c03446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Revised: 12/12/2023] [Accepted: 12/14/2023] [Indexed: 12/29/2023]
Abstract
Understanding the biological role of protein-linked glycans requires the reliable identification of glycans. Isomer separation and characterization often entail mass spectrometric detection preceded by high-performance chromatography on porous graphitic carbon. To this end, stable isotope-labeled glycans have emerged as powerful tools for retention time normalization. Hitherto, such standards were obtained by chemoenzymatic or purely enzymatic methods, which introduce, e.g., 13C-containing N-acetyl groups or galactose into native glycans. Glycan release with anhydrous hydrazine opens another route for heavy isotope introduction via concomitant de-N-acetylation. Here, we describe that de-N-acetylation can also be achieved with hydrazine hydrate, which is a more affordable and less hazardous reagent. Despite the slower reaction rate, complete conversion is achievable in 72 h at 100 °C for glycans with biantennary glycans with or without sialic acids. Shorter incubation times allow for the isolation of intermediate products with a defined degree of free amino groups, facilitating introduction of different numbers of heavy isotopes. Mass encoded glycans obtained by this versatile approach can serve a broad range of applications, e.g., as internal standards for isomer-specific studies of N-glycans, O-glycans, and human milk oligosaccharide by LC-MS on either porous graphitic carbon or─following permethylation─on reversed phase.
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Affiliation(s)
- Johannes Helm
- Department of Chemistry, University of Natural Resources and Life Sciences
Vienna, Muthgasse 18, 1190 Vienna, Austria
| | | | | | | | - Friedrich Altmann
- Department of Chemistry, University of Natural Resources and Life Sciences
Vienna, Muthgasse 18, 1190 Vienna, Austria
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5
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Liew CY, Luo HS, Yang TY, Hung AT, Magoling BJA, Lai CPK, Ni CK. Identification of the High Mannose N-Glycan Isomers Undescribed by Conventional Multicellular Eukaryotic Biosynthetic Pathways. Anal Chem 2023. [PMID: 37235553 DOI: 10.1021/acs.analchem.2c05599] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
N-linked glycosylation is one of the most important post-translational modifications of proteins. Current knowledge of multicellular eukaryote N-glycan biosynthesis suggests high mannose N-glycans are generated in the endoplasmic reticulum and Golgi apparatus through conserved biosynthetic pathways. According to conventional biosynthetic pathways, four Man7GlcNAc2 isomers, three Man6GlcNAc2 isomers, and one Man5GlcNAc2 isomer are generated during this process. In this study, we applied our latest mass spectrometry method, logically derived sequence tandem mass spectrometry (LODES/MSn), to re-examine high mannose N-glycans extracted from various multicellular eukaryotes which are not glycosylation mutants. LODES/MSn identified many high mannose N-glycan isomers previously unreported in plantae, animalia, cancer cells, and fungi. A database consisting of retention time and CID MSn mass spectra was constructed for all possible MannGlcNAc2 (n = 5, 6, 7) isomers that include the isomers by removing arbitrary numbers and positions of mannose from canonical N-glycan, Man9GlcNAc2. Many N-glycans in this database are not found in current N-glycan mass spectrum libraries. The database is useful for rapid high mannose N-glycan isomeric identification.
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Affiliation(s)
- Chia Yen Liew
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- International Graduate Program of Molecular Science and Technology, National Taiwan University (NTU-MST), Taipei 10617, Taiwan
- Molecular Science and Technology (MST), Taiwan International Graduate Program (TIGP), Academia Sinica, Taipei 10617, Taiwan
| | - Hong-Sheng Luo
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Ting-Yi Yang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan
| | - An-Ti Hung
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Bryan John Abel Magoling
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei 10617, Taiwan
- Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan
| | - Charles Pin-Kuang Lai
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Taipei 11529, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei 10617, Taiwan
| | - Chi-Kung Ni
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
- Molecular Science and Technology (MST), Taiwan International Graduate Program (TIGP), Academia Sinica, Taipei 10617, Taiwan
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan
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6
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Wang C, Gao X, Gong G, Man L, Wei Q, Lan Y, Yang M, Han J, Jin W, Wei M, Huang L, Wang Z. A versatile strategy for high-resolution separation of reducing glycan mixtures as hydrazones by two-dimensional high-performance liquid chromatography. J Chromatogr A 2022; 1685:463599. [DOI: 10.1016/j.chroma.2022.463599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 10/12/2022] [Accepted: 10/21/2022] [Indexed: 11/06/2022]
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7
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Liew CY, Chen JL, Tsai ST, Ni CK. Identification of side-reaction products generated during the ammonia-catalyzed release of N-glycans. Carbohydr Res 2022; 522:108686. [DOI: 10.1016/j.carres.2022.108686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 09/06/2022] [Accepted: 09/26/2022] [Indexed: 11/02/2022]
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8
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Melo Diaz JM, Peel SR, Spencer DI, Hendel JL. Extraction and purification of a High Mannose type oligosaccharide from Phaseolus lunatus beans by oxidative release with sodium hypochlorite. Carbohydr Res 2022; 517:108583. [DOI: 10.1016/j.carres.2022.108583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 01/20/2022] [Accepted: 05/04/2022] [Indexed: 11/30/2022]
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9
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Zhao X, Huang Y, Zhou S, Ao J, Cai H, Tanaka K, Ito Y, Ishiwata A, Ding F. Recent Chemical and Chemoenzymatic Strategies to Complex-Type N-Glycans. Front Chem 2022; 10:880128. [PMID: 35720985 PMCID: PMC9204336 DOI: 10.3389/fchem.2022.880128] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 04/12/2022] [Indexed: 12/01/2022] Open
Abstract
Glycosylation is one of the major forms of protein post-translational modification. N-glycans attached to proteins by covalent bonds play an indispensable role in intercellular interaction and immune function. In human bodies, most of the cell surface glycoproteins and secreted glycopeptides are modified with complex-type N-glycans. Thus, for analytical or medicinal purposes, efficient and universal methods to provide homogeneous complex-type N-glycans have been an urgent need. Despite the extremely complicated structures, tremendous progress in the synthesis of N-glycans has been achieved. On one hand, chemical strategies are shown to be effective to prepare core oligosaccharides of N-glycans by focusing on stereoselective glycosylations such as β-mannosylation and α-sialylation, as well as the methodology of the N-glycan assembly. On the other hand, chemoenzymatic strategies have also become increasingly powerful in recent years. This review attempts to highlight the very recent advancements in chemical and chemoenzymatic strategies for eukaryotic complex-type N-glycans.
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Affiliation(s)
- Xiaoya Zhao
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen, China
| | - Yan Huang
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen, China
| | - Siai Zhou
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen, China
| | - Jiaming Ao
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen, China
| | - Hui Cai
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen, China
- *Correspondence: Hui Cai, ; Akihiro Ishiwata, ; Feiqing Ding,
| | - Katsunori Tanaka
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo, Japan
- Alexander Butlerov Institute of Chemistry, Kazan Federal University, Kazan, Russian Federation
| | - Yukishige Ito
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- Graduate School of Science, Osaka University, Osaka, Japan
| | - Akihiro Ishiwata
- RIKEN Cluster for Pioneering Research, Saitama, Japan
- *Correspondence: Hui Cai, ; Akihiro Ishiwata, ; Feiqing Ding,
| | - Feiqing Ding
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen, China
- *Correspondence: Hui Cai, ; Akihiro Ishiwata, ; Feiqing Ding,
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10
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Tang W, Liu D, Nie SP. Food glycomics in food science: recent advances and future perspectives. Curr Opin Food Sci 2022. [DOI: 10.1016/j.cofs.2022.100850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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11
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StrucGP: de novo structural sequencing of site-specific N-glycan on glycoproteins using a modularization strategy. Nat Methods 2021; 18:921-929. [PMID: 34341581 DOI: 10.1038/s41592-021-01209-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 06/14/2021] [Indexed: 02/06/2023]
Abstract
Precision mapping of glycans at structural and site-specific level is still one of the most challenging tasks in the glycobiology field. Here, we describe a modularization strategy for de novo interpretation of N-glycan structures on intact glycopeptides using tandem mass spectrometry. An algorithm named StrucGP is also developed to automate the interpretation process for large-scale analysis. By dividing an N-glycan into three modules and identifying each module using distinct patterns of Y ions or a combination of distinguishable B/Y ions, the method enables determination of detailed glycan structures on thousands of glycosites in mouse brain, which comprise four types of core structure and 17 branch structures with three glycan subtypes. Owing to the database-independent glycan mapping strategy, StrucGP also facilitates the identification of rare/new glycan structures. The approach will be greatly beneficial for in-depth structural and functional study of glycoproteins in the biomedical research.
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12
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Structural identification of N-glycan isomers using logically derived sequence tandem mass spectrometry. Commun Chem 2021; 4:92. [PMID: 36697781 PMCID: PMC9814355 DOI: 10.1038/s42004-021-00532-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 05/19/2021] [Indexed: 01/28/2023] Open
Abstract
N-linked glycosylation is one of the most important protein post-translational modifications. Despite the importance of N-glycans, the structural determination of N-glycan isomers remains challenging. Here we develop a mass spectrometry method, logically derived sequence tandem mass spectrometry (LODES/MSn), to determine the structures of N-glycan isomers that cannot be determined using conventional mass spectrometry. In LODES/MSn, the sequences of successive collision-induced dissociation are derived from carbohydrate dissociation mechanisms and apply to N-glycans in an ion trap for structural determination. We validate LODES/MSn using synthesized N-glycans and subsequently applied this method to N-glycans extracted from soybean, ovalbumin, and IgY. Our method does not require permethylation, reduction, and labeling of N-glycans, or the mass spectrum databases of oligosaccharides and N-glycan standards. Moreover, it can be applied to all types of N-glycans (high-mannose, hybrid, and complex), as well as the N-glycans degraded from larger N-glycans by any enzyme or acid hydrolysis.
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