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Biomedical subjects

N Taniguchi

Publications and source records attributed to N Taniguchi.

At least 91 records · Page 5Linked to original sources

Effect of cAMP on inducible nitric oxide synthase gene expression: its dual and cell-specific functions.

The effects of some cAMP-elevating agents on the induction of nitric oxide synthase II (NOS II) were investigated for a macrophage-derived cell line, RAW264.7, stimulated with lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma) and the results were compared for the case of vascular smooth muscle cells (VSMC) stimulated with interleukin-1 beta (IL-1 beta). Forskolin, dibutyryl cAMP, and a phosphodiesterase inhibitor, 3-isobutyl-1-methyl xanthine, resulted in an elevated production of nitrite and nitrate, NOS II activities, NOS II mRNA accumulation, and the protein level in RAW264.7 cells stimulated with LPS or IFN-gamma. However, the addition of combinations of these reagents decreased these levels in RAW264.7 cells, but enhanced them in VSMC that had been stimulated with IL-1 beta. When intracellular cAMP levels in VSMC were measured, they were elevated by about 100 times more in the forskolin-treated cells, compared to the untreated cells. Stimulated RAW264.7 cells, on the other hand, produced much lower levels of cAMP than VSMC. It is likely that cAMP functions in two opposing directions in terms of NOS II gene induction in RAW264.7 cells in a dose-dependent manner. The effects of cAMP-elevating agents on promoter activities of the 5'-flanking region of the mouse NOS II gene were then examined. The promoter activities were enhanced in RAW264.7 cells, even in the presence of all three cAMP-elevating agents. Although the binding of NF-kappa B to responsive elements is essential for the induction of the NOS II gene, cAMP-elevating agents had no effect on NF-kappa B binding to the element, thus eliminating the involvement of NF-kappa B in the suppression of the NOS II gene by high concentrations of cAMP. These data suggest that a putative responsive element to high levels of cAMP is present outside of the region examined in this study. The inhibitory effects of cAMP in RAW264.7 cells would be due to the presence of a negative regulatory factor that is absent in VSMC.

1-Methyl-3-isobutylxanthine↗

A novel carbohydrate binding activity of annexin V toward a bisecting N-acetylglucosamine.

A bisecting GlcNAc-binding protein was purified from a Triton X-100 extract of a porcine spleen microsomal fraction using affinity chromatography, in conjunction with an agalacto bisected biantennary sugar chain-immobilized Sepharose. Since the erythroagglutinating phytohemagglutinin (E-PHA) lectin preferentially binds to sugar chains which contain the bisecting GlcNAc, during purification the binding activity of the protein was evaluated by monitoring the inhibition of lectin binding to the N-acetylglucosaminyltransferase III (GnT-III)-transfected K562 cells which express high levels of the bisecting GlcNAc. The molecular mass of the purified protein was found to be 33 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. By sequencing analysis, the isolated protein was identified as annexin V. Flow cytometric analysis showed that fluorescein-labeled annexin V binds to the GnT-III-transfected cells but not to mock cells, and that the binding was not affected by the addition of phospholipids. Furthermore, surface plasmon resonance measurements indicated that annexin V binds to the agalacto bisected biantennary sugar chain with a K(d) of 200 microM while essentially no binding was observed in the case of the corresponding non-bisected sample. These results suggest that annexin V has a novel carbohydrate binding activity and may serve as an endogenous lectin for mediating possible signals of bisecting GlcNAc, which have been implicated in a variety of biological functions.

Acetylglucosamine↗

A sequence motif involved in the donor substrate binding by alpha1,6-fucosyltransferase: the role of the conserved arginine residues.

Alpha1,6-fucosyltransferase catalyzes the transfer of fucose to the innermost GlcNAc residue of an N-linked oligosaccharide. In order to identify the amino acid residue(s) which are associated with the enzyme activity and to investigate their function, we prepared a series of mutant human alpha1,6-fucosyltransferases in which the conserved residues in the region homologous to alpha1,2-fucosyltransferase had been replaced. These proteins were then characterized by kinetic analyses. The wild-type and mutant alpha1,6-fucosyltransferases were expressed using a baculovirus-insect cell system. The activity assay showed that replacement of Arg-365 by Ala or Lys led to a complete loss of activity while substitution of Ala or Lys for the neighboring Arg-366 decreased the activity to about 3% that of the wild type. Kinetic analyses revealed that the replacements of Arg-366 lead to an increase in the apparent K (m) value for both GDP-fucose and the acceptor oligosaccharide but did not markedly affect the apparent V (max). When these mutants were inhibited by GDP in a competitive manner with respect to the donor substrate, the K (i) values were found to be 50-100 times higher than the value in the wild type. On the other hand, in the inhibition by GMP, the K (i) values for the mutants were very similar to that of the wild type. These findings suggest that Arg-366 contributes to the binding of GDP-fucose via an interaction with the beta-phosphoryl group of the GDP moiety of the donor, and that Arg-365 may also play an essential role in substrate binding. The results suggest that the motif common to alpha1,2- and alpha1,6-fucosyltransferases is critical for binding of the donor substrate, GDP-fucose.

Amino Acid Motifs↗

Genomic structure and promoter analysis of the human alpha1, 6-fucosyltransferase gene (FUT8).

GDP-L-Fuc:N-acetyl-beta-D-glucosaminide alpha1,6-fucosyltransferase (alpha1,6FucT) catalyzes the transfer of a fucosyl moiety from GDP-fucose to the asparagine-linked GlcNAc residue of complex N-glycans via alpha1,6-linkage. We have cloned the genomic DNA which encodes the human alpha1,6FucT gene ( FUT8 ) and analyzed its structure. It was found that the gene consists of at least nine exons spanning more than a 50 kbp genomic region, and the coding sequence is divided into eight exons. The translation initiation codon was located at exon 2, and thus exon 1 encodes only 5'-untranslated sequences. Transcription initiation site of FUT8 was determined by 5'-rapid amplification of the cDNA end and a primer-extension analysis using the total RNA isolated from SK-OV-3 cells, which have a high level of alpha1,6FucT activity. We then characterized the FUT8 promoter region by a reporter gene assay. The luciferase reporter assay indicated that the 5'-flanking region of exon 1, which covered about 1 kbp, conferred the promoter activity in SK-OV-3 cells. This region contains potential binding sites for some transcription factors, such as bHLH, cMyb, GATA-1, as well as a TATA-box, but not a CCAAT motif. 5'-Untranslated sequences found in ESTs and the cDNA for the FUT8 suggest the presence of an additional exon(s) at the upstream of the first exon identified in this study, and therefore, the transcription of the gene would be regulated by multiple promoters.

Base Sequence↗

Reduction of the major xenoantigen on glycosphingolipids of swine endothelial cells by various glycosyltransferases.

The effect of the various glycosyltransferases on glycosphingolipids was examined, using transfected swine endothelial cell (SEC) lines. The reactivity of parental SEC to normal human serum (NHS) and Griffonia simplicifolia IB(4) (GSIB4) lectin, which binds to the Gal alpha1-3 Gal beta 1-4 GlcNAc-R (alpha-galactosyl epitope), was reduced by approximately 20% by the treatment with D-PDMP (D-threo-1-phenyl-2-decan- oylamino-3-morpholino-1-propanol), suggesting that glycosphingolipids contained by SEC have a considerable amount of the alpha-galactosyl epitope. The overexpression of two different types of glycosyltransferase, N-acetylglucosaminyl transferase III (GnT-III), as well as alpha2, 6-sialyltransferase (ST6Gal I), alpha2,3-sialyltransferase (ST3Gal III), and alpha1,2-fucosyltransferase (alpha1,2FT), suppresses the total antigenicity of SEC significantly. However, the reduction in reactivities toward NHS and GSIB4 lectin in the case of GnT-III transfectants was milder than those in other transfectants. Western blot analysis indicated that the glycoproteins in all transfectants had diminished reactivity to NHS and GSIB4 lectin to approximately the same extent. Therefore, the neutral glycosphingolipids of these transfectants were separated by thin layer chromatography, followed by immunostaining with NHS and GSIB4 lectin. The levels of the alpha-galactosyl epitope in glycosphingolipids were not decreased in the GnT-III transfectants but were in the ST6Gal I, ST3Gal III, and alpha1,2FT transfectants. These data indicate that ST6Gal I, ST3Gal III, and alpha1,2FT reduced the alpha-galactosyl epitope in both glycoproteins and glycosphingolipids, while GnT-III reduced them only in glycoproteins.

Animals↗

Peroxiredoxin IV is a secretable protein with heparin-binding properties under reduced conditions.

Peroxiredoxins (PRxs) play a role in protecting protein free thiol groups against oxidative damage and thioredoxin-dependent peroxidase activity. This report describes the characteristics of the fourth member of the mammalian PRxs, PRx IV. Rat PRx IV produced in Sf21 cells by a baculovirus expression system has two bands with different electrophoretic mobilities, 31 and 27 kDa [Matsumoto et al. (1999) FEBS Lett. 443, 246-250]. The 27-kDa PRx IV lacks the NH(2)-terminal 36 amino acids which correspond to a predicted leader peptide, which is required for secretion from cells. Thus, the 31-kDa form is probably a precursor form, and the 27-kDa form, a secretable form which is enzymatically active. Pulse-chase experiments of PRx IV-transfected COS-1 cells showed that PRx IV is processed within 10 min and released from cells. The secretable form contains both reduced and oxidized forms. The reduced form binds to both a heparin affinity column and human umbilical vein endothelial cells, while the oxidized form does not. The equilibrium dissociation constants, K(D), for heparin and heparan sulfate as judged by surface plasmon resonance experiments were 19 and 870 nM, respectively. The secretable form corresponds to the major bands found in most tissues, as evidenced by immunoblot analysis. Within cells, secretable form was largely localized on the endoplasmic reticulum, as judged by colocalization with calreticulin. Moreover, PRx IV has glutathione-dependent peroxidase activity in addition to thioredoxin-dependent activity. These data indicate that PRx IV is a secretable protein and may exert its protective function against oxidative damage by scavenging reactive oxygen species in the extracellular space.

Animals↗

NTAKalpha and beta isoforms stimulate breast tumor cell growth by means of different receptor combinations.

Neural- and thymus-derived activator for ErbB kinases (NTAK) is a recently described member of the neuregulin family that binds directly to ErbB3 and ErbB4 and transactivates ErbB2. Rat NTAK has at least five alternative-spliced isoforms: alpha1, alpha2a, alpha2b, beta, and gamma. In order to understand their biological properties, this study focused on the NTAK alpha2a and beta isoforms, which have different EGF-like domains. The effect of these isoforms on cell growth and tyrosine phosphorylation in human breast cancer cells, MDA-MB-453 and T47D, was examined using the recombinant proteins. In terms of cell growth, NTAKalpha2a and NTAKbeta preferentially stimulate T47D cells and MDA-MB-453 cells, respectively, in a dose-dependent manner. Although both NTAKs induce the highest level of tyrosine phosphorylation of ErbB2, NTAKalpha2a and NTAKbeta preferentially induce ErbB3 and ErbB4 phosphorylation, respectively. Thus, NTAKalpha2a and NTAKbeta stimulate cell growth in different ways, by means of different combinations of receptors.

Alternative Splicing↗

Kinetic basis for the donor nucleotide-sugar specificity of beta1, 4-N-acetylglucosaminyltransferase III.

The kinetic basis of the donor substrate specificity of beta1, 4-N-acetylglucosaminyltransferase III (GnT-III) was investigated using a purified recombinant enzyme. The enzyme also transfers GalNAc and Glc moieties from their respective UDP-sugars to an acceptor at rates of 0.1-0.2% of that for GlcNAc, but Gal is not transferred at a detectable rate. Kinetic analyses revealed that these inefficient transfers, which are associated with the specificity of the enzyme, are due to the much lower V(max) values, whereas the K(m) values for UDP-GalNAc and UDP-Glc differ only slightly from that for UDP-GlcNAc. It was also found that various other nucleotide-Glc derivatives bind to the enzyme with comparable affinities to those of UDP-GlcNAc and UDP-Glc, although the derivatives do not serve as glycosyl donors. Thus, GnT-III does not appear to distinguish UDP-GlcNAc from other structurally similar nucleotide-sugars by specific binding in the ground state. These findings suggest that the specificity of GnT-III toward the nucleotide-sugar is determined during the catalytic process. This type of specificity may be efficient in preventing a possible mistransfer when other nucleotide-sugars are present in excess over the true donor.

Acetylgalactosamine↗

Localization of CD9, an enhancer protein for proheparin-binding epidermal growth factor-like growth factor, in human atherosclerotic plaques: possible involvement of juxtacrine growth mechanism on smooth muscle cell proliferation.

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), a member of the EGF family, has a potent mitogenic activity for vascular smooth muscle cells (SMCs). We previously reported that HB-EGF is involved in atherogenesis of human aorta and coronary arteries. ProHB-EGF (the membrane-anchored form of HB-EGF) has also been demonstrated to possess a mitogenic activity, which is approximately 30-fold increased when coexpressed with CD9 in mouse L cells. Thus, in the process of atherogenesis, CD9 may be involved in the proliferation of SMCs. We immunohistochemically investigated the localization of CD9 and proHB-EGF in the human aorta and coronary arteries. In normal aorta and coronary arteries, CD9 immunostaining was virtually negative, whereas proHB-EGF immunostaining was positive, especially in the arteries of babies. In contrast, in atherosclerotic lesions, some intimal SMCs were strongly positive for CD9 and proHB-EGF immunostaining. The juxtacrine growth activities of human aortic SMCs were inhibited in vitro by adding neutralization antibodies for CD9 or adding the specific inhibitor of HB-EGF. Besides, coexpressed CD9 and proHB-EGF cells markedly incorporated [(3)H]thymidine into the SMCs. CD9 is localized immunohistochemically in the SMCs of the atherosclerotic aorta and coronary arteries. CD9, when coexpressed with proHB-EGF, enhances proHB-EGF activities for SMC growth in a so-called juxtacrine manner in vitro and may be involved in atherogenesis.

Animals↗

Functional adrenocorticotropic hormone receptor in cultured human vascular endothelial cells : possible role in control of blood pressure.

Hypertension is a prominent feature of patients with Cushing's disease and ectopic adrenocorticotropic hormone (ACTH) syndrome, who have elevated ACTH levels. Chronic administration of ACTH (1-24) also raises blood pressure in humans. This effect has been postulated to be due to ACTH-induced increases in cortisol secretion in the adrenal gland. It is well known that cortisol increases vascular tone by potentiating the vasoconstrictor action of a number of pressor hormones. In the present study, we show direct evidence that human aortic endothelial cells possess the ACTH receptor. 11beta-Dehydrogenation, converting cortisol to its inactive metabolite, cortisone, mediated by vascular 11beta-hydroxysteroid dehydrogenase type 2 is essential for the control of vascular tone, and the reduced activity may be relevant to the pathogenesis of hypertension. We found that ACTH (1-24) dose-dependently decreased the gene expression and enzyme activity of 11beta-hydroxysteroid dehydrogenase type 2 in these cells, and the decrease was partially abolished by a selective ACTH receptor antagonist. This may indicate that ACTH potentiates the action of cortisol through its direct effect on the vasculature. Therefore, the present study provides important information for understanding the mechanism of ACTH-induced hypertension.

11-beta-Hydroxysteroid Dehydrogenases↗

Highly potent and orally active non-peptide arginine vasopressin antagonists for both V1A and V2 receptors: synthesis and pharmacological properties of 4'-[(4,4-difluoro-5-methylidene-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-y l)carbonyl]-2-phenylbenzanilide derivatives.

A series of compounds structurally related to 4'-[(4,4-difluoro-5-methylidene-2,3,4,5-tetrahydro-1H-1-benzoaz epin-1-yl) carbonyl]-2-phenylbenzanilide were synthesized and evaluated for arginine vasopressin (AVP) antagonistic activity. Compounds with a (Z)-olefin geometry at the 5-position of benzoazepine possessed potent affinity for both the V1A and V2 receptors. Further study has shown that one of these derivatives, (Z)-4'-(¿4,4-difluoro-5-[(4-dimethylaminopiperidino)carbonylmet hylene]-2,3,4,5-tetrahydro-1H-1-benzoazepin-1-yI¿carbonyl)2- phenylbenzanilide monohydrochloride (29, YM-35471), exhibits exceptionally potent affinity for both of V1A and V2 receptors, even when administered orally. The synthesis and pharmacological properties of this compound are detailed in this paper.

Anilides↗

Nonpeptide arginine vasopressin antagonists for both V1A and V2 receptors: synthesis and pharmacological properties of 4-(1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine-6-carbonyl)benzanili de derivatives and 4'-(5,6-dihydro-4H-thiazolo[5,4-d][1]benzoazepine-6-carbonyl)benzanilid e derivatives.

Arginine vasopressin (AVP) has a dual action mainly in the periphery, i.e., vasoconstriction and water reabsorption via V1A and V2 receptors; it may play a role in a number of diseases, including congestive heart failure (CHF), hypertension, renal disease, edema, and hyponatremia. We have attempted to develop a new series of orally active AVP antagonists for both V1A and V2 receptors based on the hypothesis that the blockade of both V1A and V2 receptors might be beneficial to CHF patients. In this report, a series of compounds structurally related to 4'-(1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine-6- carbonyl)benzanilide and 4'-(5,6-dihydro-4H- thiazolo[5,4-d][1]benzoazepine-6-carbonyl)benzanilide were synthesized and examined for AVP antagonist activity for both V1A and V2 receptors. As a result, it was found that the 4'-(1,4,5,6-tetrahydroimidazo[4,5-d][1]benzoazepine-6-carbon yl)-2- phenylbenzanilide derivatives showed potent binding affinity for both V1A and V2 receptors. Especially, 4'-(2-methyl-1,4,5,6- tetrahydroimidazo[4,5-d][1]benzoazepine-6-carbonyl)-2-phe nylbenzanilide monohydrochloride (18, YM087 = conivaptan hydrochloride) exhibited potent binding affinity and AVP antagonist activity, after intravenous administration, for both V1A and V2 receptors. Furthermore, YM087 exhibited the most potent oral activity for the V2 receptor. Details of the synthesis and pharmacological properties of this series are presented.

Administration, Oral↗

Expression and possible role of ets-1 in hepatocellular carcinoma.

Recent studies on the transcriptional factor ets-1 and carcinoma have shown that ets-1 is linked to carcinoma progression, including tumor invasion and metastasis. We studied the clinical significance of ets-1 in human hepatocellular carcinoma (HCC) by using immunohistochemical staining methods. In 99 HCC cases, the levels of ets-1 expression were analyzed in comparison with various clinicopathologic parameters, such as TNM stage, intrahepatic metastasis, histologic differentiation, and prognosis. Expression of ets-1 was scarcely detected in normal liver but markedly enhanced in noncancerous lesions adjacent to HCC lesions. In HCC lesions, ets-1 expression was observed with high incidence, although the average labeling index (LI) was lower than in noncancerous lesions. However, unexpectedly, the average LI in HCC was lower in cases of high TNM stage, poor differentiation, portal invasion, intrahepatic metastasis, large tumor size, and high Ki-67 LI. Furthermore, cases with high ets-1 expression showed better outcomes for disease-free survival than those with low ets-1 expression by univariate and multivariate analyses. These findings strongly suggest that, unlike in other neoplasms, ets-1 has a crucial role in hepatocarcinogenesis and HCC progression, especially during their early phases.

Blotting, Northern↗

Expression of N-acetylglucosaminyltransferase V in colorectal cancer correlates with metastasis and poor prognosis.

N-Acetylglucosaminyltransferase V (GnT-V) is an enzyme that catalyzes beta 1-6 branching of N-acetylglucosamine on asparagine-linked oligosaccharides of cell proteins. Metastatic potential of various cancer cells has been shown to correlate with increase of GnT-V activity and concomitant beta 1-6 branching of N-acetylglucosamine. However, protein expression of GnT-V in human cancer tissue and its clinical significance have not yet been demonstrated. To clarify the possible relationship between metastasis and GnT-V in human colorectal cancer, protein expression of GnT-V was studied using surgically resected specimens. We established a monoclonal antibody against GnT-V and performed immunohistochemical analysis of 103 human colorectal cancer cases. Of 103 cases, 26 cases (25.2 %) showed specific expression of GnT-V in colorectal cancer tissues. The expression of GnT-V was significantly correlated with distant metastasis (P < 0.05, chi2 test). Overall 5-year survival rate was 52.8% for GnT-V-positive patients and 81.7% for GnT-V-negative patients (P < 0.01, Log-rank test). We showed direct evidence for the relationship between GnT-V and metastasis in human colorectal cancer. Screening of GnT-V expression in colorectal cancer may provide useful information for prognosis of postoperative patients.

Aged↗

[Signal analysis of the ultrasonic study and recording system].

Signal processing of ultrasound has advanced from the analog system to the digital system, which provides improved images. Digital scan converter is one of the new advances and the recently developed full digital system is another. The recording system has also evolved. These techniques will contribute to the evolution of ultrasonic images.

Electronic Data Processing↗

[A case of neurogenic bladder due to neuro-Behçet disease].

Behçet disease is a systemic vasculitis of unknown cause with variable clinical features. The central nervous system may also be involved in about 10% of the patients with Behçet disease. Half of them show marked central nervous system symptoms and are diagnosed as neuro-Behçet disease. Voiding symptom is seen in about 5% of the patients with neuro-Behçet disease. We report a case of neuropathic vesico-urethral dysfunction in a 39-year-old man with neuro-Behçet disease. Its radiological and urodynamic features and treatment are also presented with some discussion.

Adult↗

The alpha1-6-fucosyltransferase gene and its biological significance.

GDP-L-Fuc:N-acetyl-beta-D-glucosaminide alpha1-6-fucosyltransferase (alpha1-6FucT) catalyzes the transfer of fucose from GDP-Fuc to N-linked type complex glycoproteins. This enzyme was purified from a human fibroblast cell line, porcine brain, a human gastric cancer cell line and human blood platelets. cDNA cloning of porcine and human alpha1-6FucT was performed from a porcine brain and gastric cancer cell cDNA libraries, respectively. Their homology is 92.2% at the nucleotide level and 95.7% at the amino acid level. No putative N-glycosylation sites were found in the predicted amino acid sequence. No homology to other fucosyltransferases such as alpha1-2FucT, alpha1-3FucT and alpha1-4FucT was found except for a region consisting of nine amino acids. The alpha1-6FucT gene is located at chromosome 14q24.3, which is also a different location from other fucosyltransferases reported to date. The alpha1-6FucT gene is the oldest gene family in the phylogenic trees among the nine cloned fucosyltransferase genes. alpha1-6FucT is widely expressed in various rat tissues and the expression of alpha1-6FucT in the liver is enhanced during hepatocarcinogenesis of LEC rats which develop hereditary hepatitis and hepatomas. In cases of human liver diseases, alpha1-6FucT is expressed in both hepatoma tissues and their surrounding tissues with chronic liver disease, but not in the case of normal liver. Serum alpha1-6-fucosylated alpha-fetoprotein (AFP) has been employed for an early diagnosis of patients with hepatoma. The mechanisms by which alpha1-6 fucosylation of AFP occurs in the hepatoma is not due to the up-regulation of alpha1-6FucT alone. Interestingly, when the alpha1-6FucT gene is transfected into Hep3B, a human hepatoma cell line, tumor formation in the liver of nude mice after splenic injection is dramatically suppressed. In this review, we focus on alpha1-6FucT and summarize its properties, gene expression and biological significance.

Animals↗

Masking and reduction of the Galactose-alpha1,3-Galactose (alpha-Gal) epitope, the major xenoantigen in swine, by the glycosyltransferase gene transfection.

The alpha-Gal epitope (Gal-alpha1-3Gal-beta1-4-GlcNAc-R), which is biosynthesized by the UDP-Gal:alpha1-3-galactosyltransferase (alpha1, 3GT), is highly associated with hyperacute rejection in swine to human xenotransplantation. A variety of strategies have been pursued to reduce or eliminate this epitope from swine tissues. Since swine ES cells are not available at present, the targeted knock out of the alpha1,3GT is restricted. Other strategies, such as enzyme competition of the alpha1,3GT with other glycosyltransferases and/or control of sugar processing by the glycosyltransferases, provide a new insight into the downregulation of the alpha-Gal epitope. This review will focus on this type of strategy, which involves a gene transfection of variety of glycosyltransferases as competitors against alpha1,3GT.

Animals↗