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Huang C, Seino J, Honda A, Fujihira H, Wu D, Okahara K, Kitazume S, Nakaya S, Kitajima K, Sato C, Suzuki T. Rat hepatocytes secrete free oligosaccharides. J Biol Chem 2024; 300:105712. [PMID: 38309509 PMCID: PMC10912633 DOI: 10.1016/j.jbc.2024.105712] [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: 08/09/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/05/2024] Open
Abstract
We recently established a method for the isolation of serum-free oligosaccharides, and characterized various features of their structures. However, the precise mechanism for how these glycans are formed still remains unclarified. To further investigate the mechanism responsible for these serum glycans, here, we utilized rat primary hepatocytes to examine whether they are able to secrete free glycans. Our findings indicated that a diverse array of free oligosaccharides such as sialyl/neutral free N-glycans (FNGs), as well as sialyl lactose/LacNAc-type glycans, were secreted into the culture medium by primary hepatocytes. The structural features of these free glycans in the medium were similar to those isolated from the sera of the same rat. Further evidence suggested that an oligosaccharyltransferase is involved in the release of the serum-free N-glycans. Our results indicate that the liver is indeed secreting various types of free glycans directly into the serum.
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Affiliation(s)
- Chengcheng Huang
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Junichi Seino
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Akinobu Honda
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Haruhiko Fujihira
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Di Wu
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Chikusa, Nagoya, Japan
| | - Kyohei Okahara
- Discovery Concept Validation Function, KAN Research Institute, Inc, Kobe, Japan
| | - Shinobu Kitazume
- Department of Clinical Laboratory Sciences, School of Health Sciences, Fukushima Medical University, Fukushima, Japan
| | - Shuichi Nakaya
- Analytical & Measuring Instruments Division, Shimadzu Corporation, Kyoto, Japan
| | - Ken Kitajima
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Chikusa, Nagoya, Japan
| | - Chihiro Sato
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Chikusa, Nagoya, Japan
| | - Tadashi Suzuki
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan.
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2
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Sugiura K, Kawai Y, Yamamoto A, Yoshioka H, Kiyohara Y, Iida A, Ozawa Y, Nishikawa M, Miura N, Hanamatsu H, Furukawa JI, Shinohara Y. Exposure to brefeldin A induces unusual expression of hybrid- and complex-type free N-glycans in HepG2 cells. Biochim Biophys Acta Gen Subj 2023; 1867:130331. [PMID: 36804277 DOI: 10.1016/j.bbagen.2023.130331] [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: 10/18/2022] [Revised: 02/09/2023] [Accepted: 02/12/2023] [Indexed: 02/18/2023]
Abstract
This study determined the effect of brefeldin A (BFA) on the free N-glycomic profile of HepG2 cells to better understand the effect of blocking intracellular vesicle formation and transport of proteins from the endoplasmic reticulum to the Golgi apparatus. A series of exoglycosidase- and endoglycosidase-assisted analyses clarified the complex nature of altered glycomic profiles. A key feature of BFA-mediated alterations in Gn2-type glycans was the expression of unusual hybrid-, monoantennary- and complex-type free N-glycans (FNGs). BFA-mediated alterations in Gn1-type glycans were characterized by the expression of unusual hybrid- and monoantennary-FNGs, without significant expression of complex-type FNGs. A time course analysis revealed that sialylated hybrid- and complex-type Gn2-type FNGs were generated later than asialo-Gn2-type FNGs, and the expression profiles of Gn2-type FNGs and N-glycans were found to be similar, suggesting that the metabolic flux of FNGs is the same as that of protein-bound N-glycans. Subcellular glycomic analysis revealed that almost all FNGs were detected in the cytoplasmic extracts. Our data suggest that hybrid-, monoantennary- and complex-type Gn2-type FNGs were cleaved from glycoproteins in the cytosol by cytosolic PNGase, and subsequently digested by cytosolic endo-β-N-acetylglucosaminidase (ENGase) to generate Gn1-type FNGs. The substrate specificity of ENGase explains the limited expression of complex Gn1 type FNGs.
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Affiliation(s)
- Kanako Sugiura
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Yuho Kawai
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Arisa Yamamoto
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Hiroki Yoshioka
- Department of Pharmacy, Gifu University of Medical Science, 4-3-3 Nijigaoka, Kani, Gifu 509-0293, Japan
| | - Yuika Kiyohara
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Ayaka Iida
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Yurika Ozawa
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Mai Nishikawa
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Nobuaki Miura
- Division of Bioinformatics, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan
| | - Hisatoshi Hanamatsu
- Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita21, Nishi11, Kita-ku, Sapporo 001-0021, Japan
| | - Jun-Ichi Furukawa
- Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita21, Nishi11, Kita-ku, Sapporo 001-0021, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Nagoya 464-8601, Japan
| | - Yasuro Shinohara
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan; Graduate School of Pharmaceutical Sciences, Kinjo Gakuin University, Nagoya 463-8521, Japan.
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3
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Durrant C, Fuehring JI, Willemetz A, Chrétien D, Sala G, Ghidoni R, Katz A, Rötig A, Thelestam M, Ermonval M, Moore SEH. Defects in Galactose Metabolism and Glycoconjugate Biosynthesis in a UDP-Glucose Pyrophosphorylase-Deficient Cell Line Are Reversed by Adding Galactose to the Growth Medium. Int J Mol Sci 2020; 21:ijms21062028. [PMID: 32188137 PMCID: PMC7139386 DOI: 10.3390/ijms21062028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/05/2020] [Accepted: 03/10/2020] [Indexed: 12/28/2022] Open
Abstract
UDP-glucose (UDP-Glc) is synthesized by UGP2-encoded UDP-Glc pyrophosphorylase (UGP) and is required for glycoconjugate biosynthesis and galactose metabolism because it is a uridyl donor for galactose-1-P (Gal1P) uridyltransferase. Chinese hamster lung fibroblasts harboring a hypomrphic UGP(G116D) variant display reduced UDP-Glc levels and cannot grow if galactose is the sole carbon source. Here, these cells were cultivated with glucose in either the absence or presence of galactose in order to investigate glycoconjugate biosynthesis and galactose metabolism. The UGP-deficient cells display < 5% control levels of UDP-Glc/UDP-Gal and > 100-fold reduction of [6-3H]galactose incorporation into UDP-[6-3H]galactose, as well as multiple deficits in glycoconjugate biosynthesis. Cultivation of these cells in the presence of galactose leads to partial restoration of UDP-Glc levels, galactose metabolism and glycoconjugate biosynthesis. The Vmax for recombinant human UGP(G116D) with Glc1P is 2000-fold less than that of the wild-type protein, and UGP(G116D) displayed a mildly elevated Km for Glc1P, but no activity of the mutant enzyme towards Gal1P was detectable. To conclude, although the mechanism behind UDP-Glc/Gal production in the UGP-deficient cells remains to be determined, the capacity of this cell line to change its glycosylation status as a function of extracellular galactose makes it a useful, reversible model with which to study different aspects of galactose metabolism and glycoconjugate biosynthesis.
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Affiliation(s)
- Christelle Durrant
- INSERM U1149, Université de Paris, 16 rue Henri Huchard, 75018 Paris, France; (C.D.); (A.W.)
| | - Jana I. Fuehring
- Institute for Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany;
| | - Alexandra Willemetz
- INSERM U1149, Université de Paris, 16 rue Henri Huchard, 75018 Paris, France; (C.D.); (A.W.)
| | - Dominique Chrétien
- UMR1163, Université Paris Decartes, Sorbonnes Paris Cité, Institut Imagine, 24 Boulevard du Montparnasse, 75015 Paris, France; (D.C.); (A.R.)
| | - Giusy Sala
- “Aldo Ravelli” Research Center and Department of Health Sciences, University of Milan, 20146 Milan, Italy; (G.S.); (R.G.)
| | - Riccardo Ghidoni
- “Aldo Ravelli” Research Center and Department of Health Sciences, University of Milan, 20146 Milan, Italy; (G.S.); (R.G.)
| | - Abram Katz
- Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Stockholm, Sweden;
| | - Agnès Rötig
- UMR1163, Université Paris Decartes, Sorbonnes Paris Cité, Institut Imagine, 24 Boulevard du Montparnasse, 75015 Paris, France; (D.C.); (A.R.)
| | - Monica Thelestam
- Department of Cell and Molecular Biology, Karolinska Institutet, 17177 Stockholm, Sweden;
| | - Myriam Ermonval
- Institut Pasteur, Department of Virology, 25 rue du Dr. Roux, 75015 Paris, France;
| | - Stuart E. H. Moore
- INSERM U1149, Université de Paris, 16 rue Henri Huchard, 75018 Paris, France; (C.D.); (A.W.)
- Correspondence:
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Hirayama H. Biology of Free Oligosaccharides: Function and Metabolism of Free N-Glycans in Eukaryote. TRENDS GLYCOSCI GLYC 2018. [DOI: 10.4052/tigg.1761.1e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Hiroto Hirayama
- Suzuki Project, T-CiRA Joint Program, Glycometabolic Biochemistry Laboratory, RIKEN
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Iminosugar antivirals: the therapeutic sweet spot. Biochem Soc Trans 2017; 45:571-582. [PMID: 28408497 PMCID: PMC5390498 DOI: 10.1042/bst20160182] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/16/2017] [Accepted: 02/27/2017] [Indexed: 01/03/2023]
Abstract
Many viruses require the host endoplasmic reticulum protein-folding machinery in order to correctly fold one or more of their glycoproteins. Iminosugars with glucose stereochemistry target the glucosidases which are key for entry into the glycoprotein folding cycle. Viral glycoproteins are thus prevented from interacting with the protein-folding machinery leading to misfolding and an antiviral effect against a wide range of different viral families. As iminosugars target host enzymes, they should be refractory to mutations in the virus. Iminosugars therefore have great potential for development as broad-spectrum antiviral therapeutics. We outline the mechanism giving rise to the antiviral activity of iminosugars, the current progress in the development of iminosugar antivirals and future prospects for this field.
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Massarweh A, Bosco M, Iatmanen-Harbi S, Tessier C, Amana L, Busca P, Chantret I, Gravier-Pelletier C, Moore SEH. Brefeldin A promotes the appearance of oligosaccharyl phosphates derived from Glc3Man9GlcNAc2-PP-dolichol within the endomembrane system of HepG2 cells. J Lipid Res 2016; 57:1477-91. [PMID: 27281477 DOI: 10.1194/jlr.m068551] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Indexed: 01/04/2023] Open
Abstract
We reported an oligosaccharide diphosphodolichol (DLO) diphosphatase (DLODP) that generates dolichyl-phosphate and oligosaccharyl phosphates (OSPs) from DLO in vitro. This enzyme could underlie cytoplasmic OSP generation and promote dolichyl-phosphate recycling from truncated endoplasmic reticulum (ER)-generated DLO intermediates. However, during subcellular fractionation, DLODP distribution is closer to that of a Golgi apparatus (GA) marker than those of ER markers. Here, we examined the effect of brefeldin A (BFA), which fuses the GA with the ER on OSP metabolism. In order to increase the steady state level of truncated DLO while allowing formation of mature DLO (Glc3Man9GlcNAc2-PP-dolichol), dolichyl-P-mannose Man7GlcNAc2-PP-dolichol mannosyltransferase was partially downregulated in HepG2 cells. We show that BFA provokes GA endomannosidase trimming of Glc3Man9GlcNAc2-PP-dolichol to yield a Man8GlcNAc2-PP-dolichol structure that does not give rise to cytoplasmic Man8GlcNAc2-P. BFA also strikingly increased OSP derived from mature DLO within the endomembrane system without affecting levels of Man7GlcNAc2-PP-dolichol or cytoplasmic Man7GlcNAc2-P. The BFA-provoked increase in endomembrane-situated OSP is sensitive to nocodazole, and BFA causes partial redistribution of DLODP activity from GA- to ER-containing regions of density gradients. These findings are consistent with BFA-provoked microtubule-dependent GA-to-ER transport of a previously reported DLODP that acts to generate a novel endomembrane-situated OSP population.
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Affiliation(s)
- Ahmad Massarweh
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France Université Pierre et Marie Curie, Paris 6, Paris, France
| | - Michaël Bosco
- Université Paris Descartes, CICB-Paris, CNRS UMR8601, LCBPT, Paris, France
| | | | - Clarice Tessier
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| | - Laura Amana
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| | - Patricia Busca
- Université Paris Descartes, CICB-Paris, CNRS UMR8601, LCBPT, Paris, France
| | - Isabelle Chantret
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| | | | - Stuart E H Moore
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
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Seino J, Fujihira H, Nakakita SI, Masahara-Negishi Y, Miyoshi E, Hirabayashi J, Suzuki T. Occurrence of free sialyl oligosaccharides related to N-glycans (sialyl free N-glycans) in animal sera. Glycobiology 2016; 26:1072-1085. [PMID: 27102284 DOI: 10.1093/glycob/cww048] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 04/01/2016] [Accepted: 04/13/2016] [Indexed: 12/23/2022] Open
Abstract
Free oligosaccharides that are structurally related to N-glycans [free N-glycans (FNGs)] are widely distributed in the cytosol of animal cells. The diverse molecular mechanisms responsible for the formation of these FNGs have been well clarified. In this study we demonstrate the wide occurrence of sialylated FNGs in sera of various animals. The features of these extracellular FNGs are quite distinct from the cytosolic FNGs, as they are Gn2-type glycans, bearing an N,N'-diacetylchitobiose unit at their reducing termini, while the cytosolic FNGs are predominantly Gn1-type, with a single GlcNAc at their reducing termini. The major structures observed varied from species to species, and the structures of the FNGs appear to be correlated with the major sialyl N-glycans on serum glycoproteins, suggesting that the serum FNGs are produced by hepatocytes. Interestingly, glycan-profiles of the FNGs indicated that they are altered in a developmental stage-dependent manner. Sialyl FNGs in the sera may not only be of biological relevance, in that they might reflect the functionality of the liver, but also can be attractive sources for obtaining uniform sialyl FNGs in the chemoenzymatic synthesis of glycoproteins.
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Affiliation(s)
- Junichi Seino
- Glycometabolome Team, RIKEN-Max Planck Institute Joint Research Center, RIKEN Global Research Cluster, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Haruhiko Fujihira
- Glycometabolome Team, RIKEN-Max Planck Institute Joint Research Center, RIKEN Global Research Cluster, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Shin-Ichi Nakakita
- Division of Functional Glycomics, Life Science Research Center, Institute of Research Promotion, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0793, Japan
| | - Yuki Masahara-Negishi
- Glycometabolome Team, RIKEN-Max Planck Institute Joint Research Center, RIKEN Global Research Cluster, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Eiji Miyoshi
- Department of Molecular Biochemistry and Clinical Investigation, Osaka University School of Medicine, 1-7 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Jun Hirabayashi
- Division of Functional Glycomics, Life Science Research Center, Institute of Research Promotion, Kagawa University, 1750-1 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0793, Japan
| | - Tadashi Suzuki
- Glycometabolome Team, RIKEN-Max Planck Institute Joint Research Center, RIKEN Global Research Cluster, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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8
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Harada Y, Hirayama H, Suzuki T. Generation and degradation of free asparagine-linked glycans. Cell Mol Life Sci 2015; 72:2509-33. [PMID: 25772500 PMCID: PMC11113800 DOI: 10.1007/s00018-015-1881-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 02/19/2015] [Accepted: 03/05/2015] [Indexed: 10/23/2022]
Abstract
Asparagine (N)-linked protein glycosylation, which takes place in the eukaryotic endoplasmic reticulum (ER), is important for protein folding, quality control and the intracellular trafficking of secretory and membrane proteins. It is known that, during N-glycosylation, considerable amounts of lipid-linked oligosaccharides (LLOs), the glycan donor substrates for N-glycosylation, are hydrolyzed to form free N-glycans (FNGs) by unidentified mechanisms. FNGs are also generated in the cytosol by the enzymatic deglycosylation of misfolded glycoproteins during ER-associated degradation. FNGs derived from LLOs and misfolded glycoproteins are eventually merged into one pool in the cytosol and the various glycan structures are processed to a near homogenous glycoform. This article summarizes the current state of our knowledge concerning the formation and catabolism of FNGs.
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Affiliation(s)
- Yoichiro Harada
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
| | - Hiroto Hirayama
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
| | - Tadashi Suzuki
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
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9
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“Three sources and three component parts” of free oligosaccharides. UKRAINIAN BIOCHEMICAL JOURNAL 2014; 86:5-17. [DOI: 10.15407/ubj86.06.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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10
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Aguilar AL, Escribano J, Wentworth P, Butters TD. Synthetic 1-Deoxynojirimycin N-Substituted Peptides Offer Prolonged Disruption to N-Linked Glycan Processing. ChemMedChem 2014; 9:2809-13. [DOI: 10.1002/cmdc.201402186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Indexed: 11/08/2022]
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Alonzi DS, Kukushkin NV, Allman SA, Hakki Z, Williams SJ, Pierce L, Dwek RA, Butters TD. Glycoprotein misfolding in the endoplasmic reticulum: identification of released oligosaccharides reveals a second ER-associated degradation pathway for Golgi-retrieved proteins. Cell Mol Life Sci 2013; 70:2799-814. [PMID: 23503623 PMCID: PMC11113499 DOI: 10.1007/s00018-013-1304-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 01/31/2013] [Accepted: 02/18/2013] [Indexed: 10/27/2022]
Abstract
Endoplasmic reticulum-associated degradation (ERAD) is a key cellular process whereby misfolded proteins are removed from the endoplasmic reticulum (ER) for subsequent degradation by the ubiquitin/proteasome system. In the present work, analysis of the released, free oligosaccharides (FOS) derived from all glycoproteins undergoing ERAD, has allowed a global estimation of the mechanisms of this pathway rather than following model proteins through degradative routes. Examining the FOS produced in endomannosidase-compromised cells following α-glucosidase inhibition has revealed a mechanism for clearing Golgi-retrieved glycoproteins that have failed to enter the ER quality control cycle. The Glc3Man7GlcNAc2 FOS species has been shown to be produced in the ER lumen by a mechanism involving a peptide: N-glycanase-like activity, and its production was sensitive to disruption of Golgi-ER trafficking. The detection of this oligosaccharide was unaffected by the overexpression of EDEM1 or cytosolic mannosidase, both of which increased the production of previously characterised cytosolically localised FOS. The lumenal FOS identified are therefore distinct in their production and regulation compared to FOS produced by the conventional route of misfolded glycoproteins directly removed from the ER. The production of such lumenal FOS is indicative of a novel degradative route for cellular glycoproteins that may exist under certain conditions.
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Affiliation(s)
- Dominic S. Alonzi
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Nikolay V. Kukushkin
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Sarah A. Allman
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Zalihe Hakki
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, VIC 3010 Australia
| | - Spencer J. Williams
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, VIC 3010 Australia
| | - Lorna Pierce
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Raymond A. Dwek
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Terry D. Butters
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
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12
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Katoh T, Takase J, Tani Y, Amamoto R, Aoshima N, Tiemeyer M, Yamamoto K, Ashida H. Deficiency of α-glucosidase I alters glycoprotein glycosylation and lifespan in Caenorhabditis elegans. Glycobiology 2013; 23:1142-51. [PMID: 23836288 DOI: 10.1093/glycob/cwt051] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Endoplasmic reticulum (ER) α-glucosidase I is an enzyme that trims the distal α1,2-linked glucose (Glc) residue from the Glc3Man9GlcNAc2 oligosaccharide following its addition to nascent glycoproteins in the initial step of processing. This reaction is critical to the subsequent processing of N-glycans and thus defects in α-glucosidase I gene in human cause congenital disorder of glycosylation (CDG) type IIb. We identified the Caenorhabditis elegans α-glucosidase I gene (F13H10.4, designated agl-1) that encodes a polypeptide with 36% identity to human α-glucosidase I. The agl-1 cDNA restored the expression of complex-type N-glycans on the cell surface of α-glucosidase I-defective Chinese hamster ovary Lec23 cells. RNAi knockdown of agl-1 [agl-1(RNAi)] produced worms that were visibly similar to wild-type, but lifespan was reduced to about half of the control. Analyses of N-glycosylation in agl-1(RNAi) animals by western blotting and mass spectrometry showed reduction of paucimannose and complex-type glycans and dramatic increase of glucosylated oligomannose glycans. In addition, a significant amount of unusual terminally fucosylated N-glycans were found in agl-1(RNAi) animals. ER stress response was also provoked, leading to the accumulation of large amounts of triglucosylated free oligosaccharides (FOSs) (Glc3Man4-5GlcNAc1-2) in agl-1(RNAi) animals. Acceleration of ER-associated degradation in response to the accumulation of unfolded glycoproteins and insufficient interaction with calnexin/calreticulin in the ER lumen likely accounts for the increase of FOSs. Taken together, these studies in C. elegans demonstrate that decreased ER α-glucosidase I affects the entire N-glycan profile and induces chronic ER stress, which may contribute to the pathophysiology of CDG-IIb in humans.
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Affiliation(s)
- Toshihiko Katoh
- Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602-4712, USA
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13
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Barker MK, Rose DR. Specificity of Processing α-glucosidase I is guided by the substrate conformation: crystallographic and in silico studies. J Biol Chem 2013; 288:13563-74. [PMID: 23536181 DOI: 10.1074/jbc.m113.460436] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The enzyme “GluI” is key to the synthesis of critical glycoproteins in the cell. RESULTS We have determined the structure of GluI, and modeled binding with its unique sugar substrate. CONCLUSION The specificity of this interaction derives from a unique conformation of the substrate. SIGNIFICANCE Understanding the mechanism of the enzyme is of basic importance and relevant to potential development of antiviral inhibitors. Processing α-glucosidase I (GluI) is a key member of the eukaryotic N-glycosylation processing pathway, selectively catalyzing the first glycoprotein trimming step in the endoplasmic reticulum. Inhibition of GluI activity impacts the infectivity of enveloped viruses; however, despite interest in this protein from a structural, enzymatic, and therapeutic standpoint, little is known about its structure and enzymatic mechanism in catalysis of the unique glycan substrate Glc3Man9GlcNAc2. The first structural model of eukaryotic GluI is here presented at 2-Å resolution. Two catalytic residues are proposed, mutations of which result in catalytically inactive, properly folded protein. Using Autodocking methods with the known substrate and inhibitors as ligands, including a novel inhibitor characterized in this work, the active site of GluI was mapped. From these results, a model of substrate binding has been formulated, which is most likely conserved in mammalian GluI.
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Affiliation(s)
- Megan K Barker
- Department of Medical Biophysics, University of Toronto, Ontario Cancer Institute, Princess Margaret Hospital, Toronto, Ontario M5G 2M9, Canada.
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14
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Demonstration that endoplasmic reticulum-associated degradation of glycoproteins can occur downstream of processing by endomannosidase. Biochem J 2011; 438:133-42. [DOI: 10.1042/bj20110186] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During quality control in the ER (endoplasmic reticulum), nascent glycoproteins are deglucosylated by ER glucosidases I and II. In the post-ER compartments, glycoprotein endo-α-mannosidase provides an alternative route for deglucosylation. Previous evidence suggests that endomannosidase non-selectively deglucosylates glycoproteins that escape quality control in the ER, facilitating secretion of aberrantly folded as well as normal glycoproteins. In the present study, we employed FOS (free oligosaccharides) released from degrading glycoproteins as biomarkers of ERAD (ER-associated degradation), allowing us to gain a global rather than single protein-centred view of ERAD. Glucosidase inhibition was used to discriminate between glucosidase- and endomannosidase-mediated ERAD pathways. Endomannosidase expression was manipulated in CHO (Chinese-hamster ovary)-K1 cells, naturally lacking a functional version of the enzyme, and HEK (human embryonic kidney)-293T cells. Endomannosidase was shown to decrease the levels of total FOS, suggesting decreased rates of ERAD. However, following pharmacological inhibition of ER glucosidases I and II, endomannosidase expression resulted in a partial switch between glucosylated FOS, released from ER-confined glycoproteins, to deglucosylated FOS, released from endomannosidase-processed glycoproteins transported from the Golgi/ERGIC (ER/Golgi intermediate compartment) to the ER. Using this approach, we have identified a previously unknown pathway of glycoprotein flow, undetectable by the commonly employed methods, in which secretory cargo is targeted back to the ER after being processed by endomannosidase.
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15
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Chantret I, Fasseu M, Zaoui K, Le Bizec C, Sadou Yayé H, Dupré T, Moore SEH. Identification of roles for peptide: N-glycanase and endo-beta-N-acetylglucosaminidase (Engase1p) during protein N-glycosylation in human HepG2 cells. PLoS One 2010; 5:e11734. [PMID: 20668520 PMCID: PMC2909182 DOI: 10.1371/journal.pone.0011734] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 06/04/2010] [Indexed: 11/29/2022] Open
Abstract
Background During mammalian protein N-glycosylation, 20% of all dolichol-linked oligosaccharides (LLO) appear as free oligosaccharides (fOS) bearing the di-N-acetylchitobiose (fOSGN2), or a single N-acetylglucosamine (fOSGN), moiety at their reducing termini. After sequential trimming by cytosolic endo β-N-acetylglucosaminidase (ENGase) and Man2c1 mannosidase, cytosolic fOS are transported into lysosomes. Why mammalian cells generate such large quantities of fOS remains unexplored, but fOSGN2 could be liberated from LLO by oligosaccharyltransferase, or from glycoproteins by NGLY1-encoded Peptide-N-Glycanase (PNGase). Also, in addition to converting fOSGN2 to fOSGN, the ENGASE-encoded cytosolic ENGase of poorly defined function could potentially deglycosylate glycoproteins. Here, the roles of Ngly1p and Engase1p during fOS metabolism were investigated in HepG2 cells. Methods/Principal Findings During metabolic radiolabeling and chase incubations, RNAi-mediated Engase1p down regulation delays fOSGN2-to-fOSGN conversion, and it is shown that Engase1p and Man2c1p are necessary for efficient clearance of cytosolic fOS into lysosomes. Saccharomyces cerevisiae does not possess ENGase activity and expression of human Engase1p in the png1Δ deletion mutant, in which fOS are reduced by over 98%, partially restored fOS generation. In metabolically radiolabeled HepG2 cells evidence was obtained for a small but significant Engase1p-mediated generation of fOS in 1 h chase but not 30 min pulse incubations. Ngly1p down regulation revealed an Ngly1p-independent fOSGN2 pool comprising mainly Man8GlcNAc2, corresponding to ∼70% of total fOS, and an Ngly1p-dependent fOSGN2 pool enriched in Glc1Man9GlcNAc2 and Man9GlcNAc2 that corresponds to ∼30% of total fOS. Conclusions/Significance As the generation of the bulk of fOS is unaffected by co-down regulation of Ngly1p and Engase1p, alternative quantitatively important mechanisms must underlie the liberation of these fOS from either LLO or glycoproteins during protein N-glycosylation. The fully mannosylated structures that occur in the Ngly1p-dependent fOSGN2 pool indicate an ERAD process that does not require N-glycan trimming.
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Affiliation(s)
- Isabelle Chantret
- INSERM, U773, Centre de Recherche Bichat Beaujon, Paris, France; Université Paris 7 Denis Diderot, site Bichat, Paris, France.
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16
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Haga Y, Totani K, Ito Y, Suzuki T. Establishment of a real-time analytical method for free oligosaccharide transport from the ER to the cytosol. Glycobiology 2009; 19:987-94. [PMID: 19494346 DOI: 10.1093/glycob/cwp075] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
During N-glycosylation of proteins, significant amounts of free unconjugated glycans are also generated in the lumen of the endoplasmic reticulum (ER). These ER-derived free glycans are translocated into the cytosol by a putative transporter on the ER membrane for further processing. However, the molecular nature of the transporter remains to be determined. Here, we report the establishment of a novel assay method for free oligosaccharide transport from the ER lumen using chemically synthesized fluorescence-labeled N-glycan derivatives. In this method, fluorescence-labeled glycan substrates were encapsulated inside mouse liver microsomes, followed by incubation with the cytosol and a fluorescence-quenching agent (anti-fluorophore antibody). The rate of substrate efflux was then monitored in real time by the decrease in the fluorescence intensity. The present data clearly demonstrated that the oligosaccharide transport activity under the current assay conditions was both ATP and cytosol dependent. The transporter activity was also found to be glycan structure specific because free glucosylated glycans were unable to be transported out of the microsomes. This new assay method will be a useful tool for identifying the transporter protein on the ER membrane.
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Affiliation(s)
- Yoshimi Haga
- Glycometabolome Team, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan
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17
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Chantret I, Moore SEH. Free oligosaccharide regulation during mammalian protein N-glycosylation. Glycobiology 2007; 18:210-24. [DOI: 10.1093/glycob/cwn003] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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18
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Alonzi DS, Neville DCA, Lachmann RH, Dwek RA, Butters TD. Glucosylated free oligosaccharides are biomarkers of endoplasmic- reticulum α-glucosidase inhibition. Biochem J 2007; 409:571-80. [PMID: 17868040 DOI: 10.1042/bj20070748] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The inhibition of ER (endoplasmic reticulum) α-glucosidases I and II by imino sugars, including NB-DNJ (N-butyl-deoxynojirimycin), causes the retention of glucose residues on N-linked oligosaccharides. Therefore, normal glycoprotein trafficking and processing through the glycosylation pathway is abrogated and glycoproteins are directed to undergo ERAD (ER-associated degradation), a consequence of which is the production of cytosolic FOS (free oligosaccharides). Following treatment with NB-DNJ, FOS were extracted from cells, murine tissues and human plasma and urine. Improved protocols for analysis were developed using ion-exchange chromatography followed by fluorescent labelling with 2-AA (2-aminobenzoic acid) and purification by lectin-affinity chromatography. Separation of 2-AA-labelled FOS by HPLC provided a rapid and sensitive method that enabled the detection of all FOS species resulting from the degradation of glycoproteins exported from the ER. The generation of oligosaccharides derived from glucosylated protein degradation was rapid, reversible, and time- and inhibitor concentration-dependent in cultured cells and in vivo. Long-term inhibition in cultured cells and in vivo indicated a slow rate of clearance of glucosylated FOS. In mouse and human urine, glucosylated FOS were detected as a result of transrenal excretion and provide unique and quantifiable biomarkers of ER-glucosidase inhibition.
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Affiliation(s)
- Dominic S Alonzi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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19
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Suzuki T, Funakoshi Y. Free N-linked oligosaccharide chains: formation and degradation. Glycoconj J 2007; 23:291-302. [PMID: 16897173 DOI: 10.1007/s10719-006-6975-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 12/21/2005] [Accepted: 12/27/2005] [Indexed: 01/09/2023]
Abstract
There is growing evidence that N-linked glycans play pivotal roles in protein folding and intra- and/or intercellular trafficking of N-glycosylated proteins. It has been shown that during the N-glycosylation of proteins, significant amounts of free oligosaccharides (free OSs) are generated in the lumen of the endoplasmic reticulum (ER) by a mechanism which remains to be clarified. Free OSs are also formed in the cytosol by enzymatic deglycosylation of misfolded glycoproteins, which are subjected to destruction by a cellular system called "ER-associated degradation (ERAD)." While the precise functions of free OSs remain obscure, biochemical studies have revealed that a novel cellular process enables them to be catabolized in a specialized manner, that involves pumping free OSs in the lumen of the ER into the cytosol where further processing occurs. This process is followed by entry into the lysosomes. In this review we summarize current knowledge about the formation, processing and degradation of free OSs in eukaryotes and also discuss the potential biological significance of this pathway. Other evidence for the occurrence of free OSs in various cellular processes is also presented.
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Affiliation(s)
- Tadashi Suzuki
- 21st COE (Center of Excellence) Program and Department of Biochemistry, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
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Yanagida K, Natsuka S, Hase S. Structural diversity of cytosolic free oligosaccharides in the human hepatoma cell line, HepG2. Glycobiology 2005; 16:294-304. [PMID: 16381657 DOI: 10.1093/glycob/cwj074] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It is thought that free oligosaccharides in the cytosol are an outcome of quality control of glycoproteins by endoplasmic reticulum-associated degradation (ERAD). Although considerable amounts of free oligosaccharides accumulate in the cytosol, where they presumably have some function, detailed analyses of their structures have not yet been carried out. We isolated 21 oligosaccharides from the cytosolic fraction of HepG2 cells and analyzed their structures by the two-dimensional high-performance liquid chromatography (HPLC) sugar-mapping method. Sixteen novel oligosaccharides were identified in the cytosol in this study. All had a single N-acetylglucosamine at their reducing-end cores and could be expressed as (Man)n (GlcNAc)1. No free oligosaccharide with N,N'-diacetylchitobiose was detected in the cytosolic fraction of HepG2 cells. This suggested that endo-beta-N-acetylglucosaminidase was a key enzyme in the production of cytosolic free oligosaccharides. The 21 oligosaccharides were classified into three series--series 1: oligosaccharides processed from Manalpha1-2Manalpha1-6 (Manalpha1-2Manalpha1-3)Manalpha1-6(Manalpha1-2Manalpha1-2Manalpha1-3) Manbeta1-4GlcNAc (M9A') and Manalpha1-2Manalpha1-6(Manalpha1-3) Manalpha1-6(Manalpha1-2Manalpha1-2Manalpha1-3)Manbeta1-4GlcNAc (M8A') by digestion with cytosolic alpha-mannosidase; series 2: oligosaccharides processed with Golgi alpha-mannosidases in addition to endoplasmic reticulum (ER) and cytosolic alpha-mannosidases; and series 3: glucosylated oligosaccharides produced from Glc1Man9GlcNAc1 by hydrolysis with cytosolic alpha-mannosidase. The presence of the series "2" oligosaccharides suggests that some of the misfolded glycoproteins had been processed in pre-cis-Golgi vesicles and/or the Golgi apparatus. When the cells were treated with swainsonine to inhibit cytosolic alpha-mannosidase, the amounts of M9A' and M8A' increased remarkably, suggesting that these oligosaccharides were translocated into the cytosol. Four oligosaccharides of series "2" also increased. In contrast, there were obvious reductions in Manalpha1-6(Manalpha1-2Manalpha1-2Manalpha1-3)Manbeta1-4GlcNAc (M5B'), the end product from M9A' by digestion with cytosolic alpha-mannosidase, and Manalpha1-6(Manalpha1- 2Manalpha1-3)Manbeta1-4GlcNAc, derived from series "2" oligosaccharides by digestion with cytosolic alpha-mannosidase. Our data suggest that (1) some of the cytosolic oligosaccharides had been processed with Golgi alpha-mannosidases, (2) the major oligosaccharides translocated from the ER were M9A' and M8A', and (3) M5B' and Glc1M5B' were maintained at relatively high concentrations in the cytosol.
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Affiliation(s)
- Kanta Yanagida
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
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Mellor H, Neville D, Harvey D, Platt F, Dwek R, Butters T. Cellular effects of deoxynojirimycin analogues: inhibition of N-linked oligosaccharide processing and generation of free glucosylated oligosaccharides. Biochem J 2004; 381:867-75. [PMID: 15128289 PMCID: PMC1133898 DOI: 10.1042/bj20031824] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2003] [Revised: 04/21/2004] [Accepted: 05/06/2004] [Indexed: 11/17/2022]
Abstract
In the accompanying paper [Mellor, Neville, Harvey, Platt, Dwek and Butters (2004) Biochem. J. 381, 861-866] we treated HL60 cells with N-alk(en)yl-deoxynojirimycin (DNJ) compounds to inhibit glucosphingolipid (GSL) biosynthesis and identified a number of non-GSL-derived, small, free oligosaccharides (FOS) most likely produced due to inhibition of the oligosaccharide-processing enzymes a-glucosidases I and II. When HL60 cells were treated with concentrations of N-alk(en)ylated DNJ analogues that inhibited GSL biosynthesis completely, N-butyl- and N-nonyl-DNJ inhibited endoplasmic reticulum (ER) glucosidases I and II, but octadecyl-DNJ did not, probably due to the lack of ER lumen access for this novel, long-chain derivative. Glucosidase inhibition resulted in the appearance of free Glc1-3Man structures, which is evidence of Golgi glycoprotein endomannosidase processing of oligosaccharides with retained glucose residues. Additional large FOS was also detected in cells following a 16 h treatment with N-butyl- and N-nonyl-DNJ. When these FOS structures (>30, including >20 species not present in control cells) were characterized by enzyme digests and MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS, all were found to be polymannose-type oligosaccharides, of which the majority were glucosylated and had only one reducing terminal GlcNAc (N-acetylglucosamine) residue (FOS-GlcNAc1), demonstrating a cytosolic location. These results support the proposal that the increase in glucosylated FOS results from enzyme-mediated cytosolic cleavage of oligosaccharides from glycoproteins exported from the ER because of misfolding or excessive retention. Importantly, the present study characterizes the cellular properties of DNJs further and demonstrates that side-chain modifications allow selective inhibition of protein and lipid glycosylation pathways. This represents the most detailed characterization of the FOS structures arising from ER a-glucosidase inhibition to date.
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Affiliation(s)
- Howard R. Mellor
- Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K
| | - David C. A. Neville
- Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K
| | - David J. Harvey
- Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K
| | - Frances M. Platt
- Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K
| | - Raymond A. Dwek
- Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K
| | - Terry D. Butters
- Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K
- To whom correspondence should be addressed (e-mail )
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van Huystee RB, Sun Y, Lige B. A retrospective look at the cationic peanut peroxidase structure. Crit Rev Biotechnol 2003; 22:335-54. [PMID: 12487424 DOI: 10.1080/07388550290789540] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The cationic peanut peroxidase has been studied in detail, not only with regard to its peptide structure, but also to the sites and role of the three moieties linked to it. Peanut peroxidase lends itself well to a close examination as a potential example for other plant peroxidase studies. It was the first plant peroxidase for which a 3-D structure was derived from crystals, with the glycans intact. Subsequent analysis of peroxidases structures from other plants have not shown great differences to that of the peanut peroxidase. As the period of proteomics follows on the era of genomics, the study of glycans has been brought back into focus. With the potential use of peroxidase as a polymerization agent for industry, there are some aspects of the overall structure that should be kept in mind for successful use of this enzyme. A variety of techniques are now available to assay for these structures/moieties and their roles. Peanut peroxidase data are reviewed in that light, as well as defining some true terms for isozymes. Because a high return of the enzyme in a pure form has been obtained from cultured cells in suspension culture, a brief review of this is also offered.
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Affiliation(s)
- Robert B van Huystee
- Department of Plant Sciences, The University of Western Ontario, London, Ontario, N6A 5B7, Canada.
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Pathways and functions of mammalian protein glycosylation. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0167-7306(03)38026-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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