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Garry L Taylor - One of the best experts on this subject based on the ideXlab platform.
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Streptococcus pneumoniae NanC: STRUCTURAL INSIGHTS INTO THE SPECIFICITY AND MECHANISM OF A Sialidase THAT PRODUCES A Sialidase INHIBITOR.
Journal of Biological Chemistry, 2015Co-Authors: C. David Owen, Garry L Taylor, Petra Lukacik, Jane A. Potter, Olivia Sleator, Martin A. WalshAbstract:Streptococcus pneumoniae is an important human pathogen that causes a range of disease states. Sialidases are important bacterial virulence factors. There are three pneumococcal Sialidases: NanA, NanB, and NanC. NanC is an unusual Sialidase in that its primary reaction product is 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (Neu5Ac2en, also known as DANA), a nonspecific hydrolytic Sialidase inhibitor. The production of Neu5Ac2en from α2–3-linked sialosides by the catalytic domain is confirmed within a crystal structure. A covalent complex with 3-fluoro-β-N-acetylneuraminic acid is also presented, suggesting a common mechanism with other Sialidases up to the final step of product formation. A conformation change in an active site hydrophobic loop on ligand binding constricts the entrance to the active site. In addition, the distance between the catalytic acid/base (Asp-315) and the ligand anomeric carbon is unusually short. These features facilitate a novel Sialidase reaction in which the final step of product formation is direct abstraction of the C3 proton by the active site aspartic acid, forming Neu5Ac2en. NanC also possesses a carbohydrate-binding module, which is shown to bind α2–3- and α2–6-linked sialosides, as well as N-acetylneuraminic acid, which is captured in the crystal structure following hydration of Neu5Ac2en by NanC. Overall, the pneumococcal Sialidases show remarkable mechanistic diversity while maintaining a common structural scaffold.
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the aspergillus fumigatus Sialidase is a 3 deoxy d glycero d galacto 2 nonulosonic acid hydrolase kdnase structural and mechanistic insights
Journal of Biological Chemistry, 2011Co-Authors: Judith C Telford, Milton J Kiefel, Andrew G Watts, Juliana H. F. Yeung, Andrew J. Bennet, Margo M. Moore, Stefan Hader, Jefferson Y Chan, Garry L TaylorAbstract:Abstract Aspergillus fumigatus is a filamentous fungus that can cause severe respiratory disease in immunocompromised individuals. A putative Sialidase from A. fumigatus was recently cloned and shown to be relatively poor in cleaving N-acetylneuraminic acid (Neu5Ac) in comparison with bacterial Sialidases. Here we present the first crystal structure of a fungal Sialidase. When the apo structure was compared with bacterial Sialidase structures, the active site of the Aspergillus enzyme suggested that Neu5Ac would be a poor substrate because of a smaller pocket that normally accommodates the acetamido group of Neu5Ac in Sialidases. A sialic acid with a hydroxyl in place of an acetamido group is 2-keto-3-deoxynononic acid (KDN). We show that KDN is the preferred substrate for the A. fumigatus Sialidase and that A. fumigatus can utilize KDN as a sole carbon source. A 1.45-A resolution crystal structure of the enzyme in complex with KDN reveals KDN in the active site in a boat conformation and nearby a second binding site occupied by KDN in a chair conformation, suggesting that polyKDN may be a natural substrate. The enzyme is not inhibited by the Sialidase transition state analog 2-deoxy-2,3-dehydro-N-acetylneuraminic acid (Neu5Ac2en) but is inhibited by the related 2,3-didehydro-2,3-dideoxy-d-glycero-d-galacto-nonulosonic acid that we show bound to the enzyme in a 1.84-A resolution crystal structure. Using a fluorinated KDN substrate, we present a 1.5-A resolution structure of a covalently bound catalytic intermediate. The A. fumigatus Sialidase is therefore a KDNase with a similar catalytic mechanism to Neu5Ac exoSialidases, and this study represents the first structure of a KDNase.
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structural studies on the pseudomonas aeruginosa Sialidase like enzyme pa2794 suggest substrate and mechanistic variations
Journal of Molecular Biology, 2009Co-Authors: Charlotte Ryan, Milton J Kiefel, Jennifer C Wilson, Garry L TaylorAbstract:Pseudomonas aeruginosa encodes an enzyme (PA2794) that is annotated as a Sialidase (or neuraminidase), as it possesses three bacterial neuraminidase repeats that are a signature of nonviral Sialidases. A recent report showed that when the gene encoding this Sialidase is knocked out, this led to a reduction in biofilm production in the lungs of mice, and it was suggested that the enzyme recognizes pseudaminic acid, a sialic acid analogue that decorates the flagella of Pseudomonas, Helicobacter, and Campylobacter species. Here, we present the crystal structure of the P. aeruginosa enzyme and show that it adopts a trimeric structure, partly held together by an immunoglobulin-like trimerization domain that is C-terminal to a classical beta-propeller Sialidase domain. The recombinant enzyme does not show any Sialidase activity with the standard fluorogenic sialic-acid-based substrate. The proposed active site contains certain conserved features of a Sialidase: a nucleophilic tyrosine with its associated glutamic acid, and two of the usual three arginines that interact with the carboxylic acid group of the substrate, but is missing the first arginine and the aspartic acid that acts as an acid/base in all Sialidases studied to date. We show, by in silico docking, that the active site may accommodate pseudaminic acid but not sialic acid and that this is due, in part, to a phenylalanine in the hydrophobic pocket that selects for the alternative stereochemistry of pseudaminic acid at C5 compared to sialic acid. Mutation of this phenylalanine to an alanine converts the enzyme into a Sialidase, albeit a poor one, which we confirm by kinetics and NMR, and this allowed us to probe the function of other amino acids. We propose that a histidine plays the role of the acid/base, whose state is altered through a charge-relay system involving a novel His-Tyr-Glu triad. The location of this relay system precludes the presence of one of the three arginines usually found in a Sialidase active site.
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Structural Studies on the Pseudomonas aeruginosa Sialidase-Like Enzyme PA2794 Suggest Substrate and Mechanistic Variations
Journal of Molecular Biology, 2009Co-Authors: Guogang Xu, Charlotte Ryan, Milton J Kiefel, Jennifer C Wilson, Garry L TaylorAbstract:Abstract Pseudomonas aeruginosa encodes an enzyme (PA2794) that is annotated as a Sialidase (or neuraminidase), as it possesses three bacterial neuraminidase repeats that are a signature of nonviral Sialidases. A recent report showed that when the gene encoding this Sialidase is knocked out, this led to a reduction in biofilm production in the lungs of mice, and it was suggested that the enzyme recognizes pseudaminic acid, a sialic acid analogue that decorates the flagella of Pseudomonas, Helicobacter, and Campylobacter species. Here, we present the crystal structure of the P. aeruginosa enzyme and show that it adopts a trimeric structure, partly held together by an immunoglobulin-like trimerization domain that is C-terminal to a classical β-propeller Sialidase domain. The recombinant enzyme does not show any Sialidase activity with the standard fluorogenic sialic-acid-based substrate. The proposed active site contains certain conserved features of a Sialidase: a nucleophilic tyrosine with its associated glutamic acid, and two of the usual three arginines that interact with the carboxylic acid group of the substrate, but is missing the first arginine and the aspartic acid that acts as an acid/base in all Sialidases studied to date. We show, by in silico docking, that the active site may accommodate pseudaminic acid but not sialic acid and that this is due, in part, to a phenylalanine in the hydrophobic pocket that selects for the alternative stereochemistry of pseudaminic acid at C5 compared to sialic acid. Mutation of this phenylalanine to an alanine converts the enzyme into a Sialidase, albeit a poor one, which we confirm by kinetics and NMR, and this allowed us to probe the function of other amino acids. We propose that a histidine plays the role of the acid/base, whose state is altered through a charge-relay system involving a novel His-Tyr-Glu triad. The location of this relay system precludes the presence of one of the three arginines usually found in a Sialidase active site.
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identification of a Sialidase encoded in the human major histocompatibility complex
Journal of Biological Chemistry, 1997Co-Authors: Caroline M Milner, Garry L Taylor, Sandra V Smith, Belen M Carrillo, Michael Hollinshead, Duncan R CampbellAbstract:Mammalian Sialidases are important in modulating the sialic acid content of cell-surface and intracellular glycoproteins. However, the full extent of this enzyme family and the physical and biochemical properties of its individual members are unclear. We have identified a novel gene, G9, in the human major histocompatibility complex (MHC), that encodes a 415-amino acid protein sharing 21-28% sequence identity with the bacterial Sialidases and containing three copies of the Asp-block motif characteristic of these enzymes. The level of sequence identity between human G9 and a cytosolic Sialidase identified in rat and hamster (28-29%) is much less than would be expected for analogous proteins in these species, suggesting that G9 is distinct from the cytosolic enzyme. Expression of G9 in insect cells has confirmed that it encodes a Sialidase, which shows optimal activity at pH 4.6, but appears to have limited substrate specificity. The G9 protein carries an N-terminal signal sequence and immunofluorescence staining of COS7 cells expressing recombinant G9 shows localization of this Sialidase exclusively to the endoplasmic reticulum. The location of the G9 gene, within the human MHC, corresponds to that of the murine Neu-1 locus, suggesting that these are analogous genes. One of the functions attributed to Neu-1 is the up-regulation of Sialidase activity during T cell activation.
Taeko Miyagi - One of the best experts on this subject based on the ideXlab platform.
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Structure and Function of Mammalian Sialidases
Topics in Current Chemistry, 2012Co-Authors: Eugenio Monti, Taeko MiyagiAbstract:The removal of sialic acids, catalyzed by Sialidase, is the initial step in degradation of oligosaccharides, glycoproteins, and glycolipids. The catalytic reaction may greatly influence biological processes through changing the conformation of glycoproteins and create or mask binding sites of functional molecules. Recent progress in Sialidase research has clarified that mammalian Sialidases indeed contribute to the regulation of various cellular functions as well as lysosomal catabolism, unlike the Sialidases of microbial origin that probably play roles limited to nutrition and pathogenesis. However, the mammalian enzymes contain consensus sequences in the six-blade β-propeller structural organization typical of microbial Sialidases, despite the low degree of similarity to the amino acid sequences of the microbial enzymes. The present review briefly summarizes structural and functional features of mammalian Sialidases.
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Altered expression of Sialidases in human cancer.
Advances in Experimental Medicine and Biology, 2012Co-Authors: Taeko Miyagi, Setsuko Moriya, Keiko Hata, Tadashi Wada, Kohta Takahashi, Kazunori Yamaguchi, Koji Yamamoto, Kazuhiro ShiozakiAbstract:Sialidases are glycosidases catalyzing the removal of α-glycosidically linked sialic acid residues from carbohydrate groups of glycoproteins and glycolipids, which is the initial step in degradation of the glycoconjugates. Four types of human Sialidases have been identified, characterized, and designated as NEU1, NEU2, NEU3, and NEU4, according to their major subcellular localization and enzymatic properties. Each Sialidase has been found to play a unique role depending on its particular properties. The present review briefly summarizes mainly our recent results on aberrant expression and pathological roles of human Sialidases in cancer.
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design synthesis and biological evaluation of human Sialidase inhibitors part 1 selective inhibitors of lysosomal Sialidase neu1
Bioorganic & Medicinal Chemistry Letters, 2008Co-Authors: Sadagopan Magesh, Setsuko Moriya, Taeko Miyagi, Hideharu Ishida, Tohru Suzuki, Makoto KisoAbstract:We here report the design and synthesis of selective human lysosomal Sialidase (NEU1) inhibitors. A series of amide-linked C9 modified DANA (2-deoxy-2,3-dehydro-N-acetylneuraminic acid) analogues were synthesized and their inhibitory activities against all four human Sialidases (NEU1–NEU4) were determined. Structure-based approach was used to investigate the basis of selectivity of the compounds with experimentally observed activity. Results from the present study are found to be informative in a qualitative manner for the further design of isoform selective human Sialidase inhibitors for therapeutic value.
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Human Sialidase as a cancer marker.
PROTEOMICS, 2008Co-Authors: Taeko Miyagi, Kazuhiro Shiozaki, Tadashi Wada, Ikuro Sato, Kazunori Yamaguchi, Yoichiro Kakugawa, Hideaki Yamanami, Tsuneaki FujiyaAbstract:Altered sialylation of cell surface glycoproteins and glycolipids is closely related to the malignant phenotype of cancer cells, including the metastatic potential and invasiveness. Many cancer-related antigens in clinical use contain sialic acids at the terminal position of sugar chains in the molecules. To elucidate the molecular mechanism, we focused our investigation on Sialidase, which catalyzes the removal of sialic acid residues from the glycoconjugates. Four types of human Sialidases identified to date behave in different manners during carcinogenesis. One of the Sialidases, found in the lysosomes, showed downregulation in cancers, promoting anchorage-independent growth, and metastatic ability, while another, found in the plasma membrane, showed marked upregulation, causing apoptosis suppression. It was found that estimation of the mRNA levels of Sialidases by real-time PCR allowed discrimination of cancerous from noncancerous tissues and even determination of the pathological stage in some cancers. Immunohistochemistry of cancer tissues using the antibody against the plasma membrane Sialidase was useful for clinical diagnosis. This paper briefly summarizes our findings of the altered Sialidase expression in cancers and the possibility of their clinical application as cancer markers. Human Sialidases are indeed related to malignancy and may be potential targets for cancer diagnosis and therapy.
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Sialidase and malignancy: a minireview.
Glycoconjugate Journal, 2003Co-Authors: Taeko Miyagi, Tadashi Wada, Kazunori Yamaguchi, Keiko HataAbstract:Aberrant sialylation in cancer cells is thought to be a characteristic feature associated with malignant properties including invasiveness and metastatic potential. Sialidase which catalyzes the removal of sialic acid residues from glycoproteins and glycolipids, has been suggested to play important roles in many biological processes through regulation of cellular sialic acid contents. The altered expression of Sialidase observed in cancer would, therefore, suggest its involvement in the malignant process. In mammalian cells, three types of Sialidase cloned and characterized to date were found to behave in different manners during carcinogenesis. Recent progress in molecular cloning of these Sialidases has facilitated elucidation of the molecular mechanisms and significance of these alterations. Herein we briefly describe our own studies on Sialidase changes associated with malignant transformation and summarize the topic from both a retrospective and a prospective viewpoint. Sialidases are indeed closely related to malignancy and are thus potential targets for cancer diagnosis and therapy. Published in 2004.
Yoji Tsukada - One of the best experts on this subject based on the ideXlab platform.
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arthrobacter ureafaciens Sialidase isoenzymes l m1 and m2 cleave fucosyl gm1
Glycoconjugate Journal, 1997Co-Authors: Masao Iwamori, Yasuhiro Ohta, Yoshihiro Uchida, Yoji TsukadaAbstract:Among bacterial, fungal and viral Sialidases, the Sialidase from Arthrobacter ureafaciens has the unique property of cleaving sialic acids linked to the internal galactose of gangliotetraose. In this study, we examined the ability to cleave the internal sialic acids of GM1 and fucosyl GM1 of Sialidases from several bacterial and fungal origins, including Clostridium perfringens and Vibrio cholerae. We found that A. ureafaciens Sialidase could liberate the sialic acid of GM1 at the highest rate, and was the only enzyme which could cleave fucosyl GM1 among the Sialidases examined.
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Arthrobacter ureafaciens Sialidase isoenzymes, L, M1 and M2, cleave fucosyl GM1
Glycoconjugate Journal, 1997Co-Authors: Masao Iwamori, Yasuhiro Ohta, Yoshihiro Uchida, Yoji TsukadaAbstract:Among bacterial, fungal and viral Sialidases, the Sialidase from Arthrobacter ureafaciens has the unique property of cleaving sialic acids linked to the internal galactose of gangliotetraose. In this study, we examined the ability to cleave the internal sialic acids of GM1 and fucosyl GM1 of Sialidases from several bacterial and fungal origins, including Clostridium perfringens and Vibrio cholerae. We found that A. ureafaciens Sialidase could liberate the sialic acid of GM1 at the highest rate, and was the only enzyme which could cleave fucosyl GM1 among the Sialidases examined. The affinity-purified Sialidase derived from the culture medium of A. ureafaciens was comprised of four isoenzymes with different molecular weights and isoelectric points, the isoenzymes that cleaved fucosyl GM1 being L (88 kDa, pI 5.0), M1 (66 kDa, pI 6.2) and M2 (66 kDa, pI 5.5), but not S (52 kDa, pI 6.2) which showed the highest specific activity toward colominic acid among the four isoenzymes. Abbreviations: SA, sialic acid; PBS, phosphate-buffered saline; PVP, polyvinylpyrrolidone; FABMS, fast atom bombardment mass spectrometry; Galβint, internal galactose of Gg4Cer; Galβext, external galactose of Gg4Cer
Masao Iwamori - One of the best experts on this subject based on the ideXlab platform.
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arthrobacter ureafaciens Sialidase isoenzymes l m1 and m2 cleave fucosyl gm1
Glycoconjugate Journal, 1997Co-Authors: Masao Iwamori, Yasuhiro Ohta, Yoshihiro Uchida, Yoji TsukadaAbstract:Among bacterial, fungal and viral Sialidases, the Sialidase from Arthrobacter ureafaciens has the unique property of cleaving sialic acids linked to the internal galactose of gangliotetraose. In this study, we examined the ability to cleave the internal sialic acids of GM1 and fucosyl GM1 of Sialidases from several bacterial and fungal origins, including Clostridium perfringens and Vibrio cholerae. We found that A. ureafaciens Sialidase could liberate the sialic acid of GM1 at the highest rate, and was the only enzyme which could cleave fucosyl GM1 among the Sialidases examined.
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Arthrobacter ureafaciens Sialidase isoenzymes, L, M1 and M2, cleave fucosyl GM1
Glycoconjugate Journal, 1997Co-Authors: Masao Iwamori, Yasuhiro Ohta, Yoshihiro Uchida, Yoji TsukadaAbstract:Among bacterial, fungal and viral Sialidases, the Sialidase from Arthrobacter ureafaciens has the unique property of cleaving sialic acids linked to the internal galactose of gangliotetraose. In this study, we examined the ability to cleave the internal sialic acids of GM1 and fucosyl GM1 of Sialidases from several bacterial and fungal origins, including Clostridium perfringens and Vibrio cholerae. We found that A. ureafaciens Sialidase could liberate the sialic acid of GM1 at the highest rate, and was the only enzyme which could cleave fucosyl GM1 among the Sialidases examined. The affinity-purified Sialidase derived from the culture medium of A. ureafaciens was comprised of four isoenzymes with different molecular weights and isoelectric points, the isoenzymes that cleaved fucosyl GM1 being L (88 kDa, pI 5.0), M1 (66 kDa, pI 6.2) and M2 (66 kDa, pI 5.5), but not S (52 kDa, pI 6.2) which showed the highest specific activity toward colominic acid among the four isoenzymes. Abbreviations: SA, sialic acid; PBS, phosphate-buffered saline; PVP, polyvinylpyrrolidone; FABMS, fast atom bombardment mass spectrometry; Galβint, internal galactose of Gg4Cer; Galβext, external galactose of Gg4Cer
Tadashi Wada - One of the best experts on this subject based on the ideXlab platform.
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Increased Sialidase activity in serum of cancer patients: Identification of Sialidase and inhibitor activities in human serum.
Cancer Science, 2015Co-Authors: Keiko Hata, Setsuko Moriya, Kazuhiro Shiozaki, Tadashi Wada, Tatsuo Tochigi, Ikuro Sato, Sadafumi Kawamura, Kohta Takahashi, Kazunori Yamaguchi, Masahiro HosonoAbstract:Aberrant sialylation in glycoproteins and glycolipids is a characteristic feature of malignancy. Human Sialidases, which catalyze the removal of sialic acid residues from glycoconjugates, have been implicated in cancer progression. They have been detected in a wide variety of human cells and tissues, but few studies have focused on their existence in human serum. Among the four types identified to date, we previously demonstrated that plasma membrane-associated ganglioside Sialidase (NEU3) is markedly upregulated in various human cancers, including examples in the colon and prostate. Here, using a sensitive assay method, we found a significant increase of Sialidase activity in the serum of patients with prostate cancer compared with that in healthy subjects having low activity, if any. Activity was apparent with gangliosides as substrates, but only to a very limited extent with 4-methylumbelliferyl sialic acid, a good synthetic substrate for Sialidases other than human NEU3. The serum Sialidase was also almost entirely immunoprecipitated with anti-NEU3 antibody, but not with antibodies for other Sialidases. Interestingly, sera additionally contained inhibitory activity against the Sialidase and also against recombinant human NEU3. The Sialidase and inhibitor activities could be separated by exosome isolation and by hydrophobic column chromatography. The serum Sialidase was assessed by a sandwich ELISA method using two anti-NEU3 antibodies. The results provide strong evidence that the serum Sialidase is, in fact, NEU3, and this subtype may, therefore, be a potential utility for novel diagnosis of human cancers.
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Altered expression of Sialidases in human cancer.
Advances in Experimental Medicine and Biology, 2012Co-Authors: Taeko Miyagi, Setsuko Moriya, Keiko Hata, Tadashi Wada, Kohta Takahashi, Kazunori Yamaguchi, Koji Yamamoto, Kazuhiro ShiozakiAbstract:Sialidases are glycosidases catalyzing the removal of α-glycosidically linked sialic acid residues from carbohydrate groups of glycoproteins and glycolipids, which is the initial step in degradation of the glycoconjugates. Four types of human Sialidases have been identified, characterized, and designated as NEU1, NEU2, NEU3, and NEU4, according to their major subcellular localization and enzymatic properties. Each Sialidase has been found to play a unique role depending on its particular properties. The present review briefly summarizes mainly our recent results on aberrant expression and pathological roles of human Sialidases in cancer.
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Human Sialidase as a cancer marker.
PROTEOMICS, 2008Co-Authors: Taeko Miyagi, Kazuhiro Shiozaki, Tadashi Wada, Ikuro Sato, Kazunori Yamaguchi, Yoichiro Kakugawa, Hideaki Yamanami, Tsuneaki FujiyaAbstract:Altered sialylation of cell surface glycoproteins and glycolipids is closely related to the malignant phenotype of cancer cells, including the metastatic potential and invasiveness. Many cancer-related antigens in clinical use contain sialic acids at the terminal position of sugar chains in the molecules. To elucidate the molecular mechanism, we focused our investigation on Sialidase, which catalyzes the removal of sialic acid residues from the glycoconjugates. Four types of human Sialidases identified to date behave in different manners during carcinogenesis. One of the Sialidases, found in the lysosomes, showed downregulation in cancers, promoting anchorage-independent growth, and metastatic ability, while another, found in the plasma membrane, showed marked upregulation, causing apoptosis suppression. It was found that estimation of the mRNA levels of Sialidases by real-time PCR allowed discrimination of cancerous from noncancerous tissues and even determination of the pathological stage in some cancers. Immunohistochemistry of cancer tissues using the antibody against the plasma membrane Sialidase was useful for clinical diagnosis. This paper briefly summarizes our findings of the altered Sialidase expression in cancers and the possibility of their clinical application as cancer markers. Human Sialidases are indeed related to malignancy and may be potential targets for cancer diagnosis and therapy.
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Sialidase and malignancy: a minireview.
Glycoconjugate Journal, 2003Co-Authors: Taeko Miyagi, Tadashi Wada, Kazunori Yamaguchi, Keiko HataAbstract:Aberrant sialylation in cancer cells is thought to be a characteristic feature associated with malignant properties including invasiveness and metastatic potential. Sialidase which catalyzes the removal of sialic acid residues from glycoproteins and glycolipids, has been suggested to play important roles in many biological processes through regulation of cellular sialic acid contents. The altered expression of Sialidase observed in cancer would, therefore, suggest its involvement in the malignant process. In mammalian cells, three types of Sialidase cloned and characterized to date were found to behave in different manners during carcinogenesis. Recent progress in molecular cloning of these Sialidases has facilitated elucidation of the molecular mechanisms and significance of these alterations. Herein we briefly describe our own studies on Sialidase changes associated with malignant transformation and summarize the topic from both a retrospective and a prospective viewpoint. Sialidases are indeed closely related to malignancy and are thus potential targets for cancer diagnosis and therapy. Published in 2004.
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Differential Expression of Three Sialidase Genes in Rat Development
Biochemical and Biophysical Research Communications, 2001Co-Authors: Takafumi Hasegawa, Carmen Feijoo Carnero, Tadashi Wada, Yasuto Itoyama, Taeko MiyagiAbstract:Mammalian Sialidases have been reported to give a great influence on a number of cellular functions including cell differentiation and cell growth by removal of sialic acids from glycoproteins and gangliosides. To understand the roles of the Sialidases during development, we investigated expression pattern of three types of Sialidase in developing rat brain and liver. For this purpose we cloned a new membrane-associated Sialidase cDNA from rat brain. The cDNA encodes 418 amino acids containing three ASP-boxes characteristic of Sialidases and the major transcript of 3.5 kb is highly expressed in brain and cardiac muscle but low in liver. Competitive polymerase chain reaction methods were developed to evaluate the mRNA level together with activity assays in comparison with cytosolic and lysosomal Sialidases previously obtained. The results indicate that the expression of individual Sialidase genes is spatiotemporally controlled with distinct roles in determining the concentration and components of sialo-glycoconjugates during development.
