• Journal of Microbiology and Biotechnology
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• v.23 no.5
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• pp.699-706
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• 2013

We have previously reported that N-acetylcysteine (NAC) not only delayed apoptosis but also enhanced the production of recombinant erythropoietin (EPO) in Chinese hamster ovary (CHO) cell culture. To investigate the production enhancement mechanism, the effects of similar thiol-reducing agents were studied. Intriguingly, all mild reducing agents examined including mercaptoethanesulfonic acid (MESNA), thiolactic acid (TLA), and thioglycolate (TG) were shown to block apoptosis and increase EPO production. A pulse-chase study of EPO secretion revealed that all four thiol-reducing agents increased the EPO secretion rate; among them TLA showed the highest rate. In terms of product quality, the sialic acid content of the glycoprotein is one of the most important factors. It was reported that a number of glycoproteins produced by CHO cells often have incomplete sialylation, particularly under high-producing conditions. Human ${\alpha}2,3$-sialyltransferase (${\alpha}2,3$-ST) was introduced into EPO-producing CHO cells in order to compensate for the reduced sialylation during supplementation with NAC. When ${\alpha}2,3$-ST was expressed in the presence of NAC, reduced sialylation was restored and an even more sialylated EPO was produced. Thus, our study is significant in that it offers increased EPO production while still allowing the prevention of decreased sialylation of EPO.

• Animal cells and systems
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• v.3 no.3
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• pp.253-258
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• 1999

The present study describes histochemical properties of the mucosubstances in the pedal sole of abalone, in relation to two main additional functions known to date. Only neutral mucosubstances were demonstrated in the lateral epithelium of the pedal sole of the abalone, however, two distinct types of cells, one containing neutral and the other containing acidic mucosubstances, were identified in the ventral epithelium. The epithelial mucocytes distributed throughout both epithelial and subepithelial glands located in the ventral subepithelial region showed a mixture of neutral and acidic mucosubstances. However, acidic mucosubstances were found in larger amounts than neutral ones in epithelial mucocytes, and vice versa in subepithelial glands. Among these acidic mucosubstances, sulphated substances were dominant. Lesser amounts of carboxylated substances also occurred together with low levels of neuramic and sialic acid. Collectively, the notable morphological differences between abalone and other gastropoda were observed in the ventral surface of the foot, which showed a tall columnar epithelium, peripherally concentrated mucocytes, and subepithelial glands. Mucosubstances are presumably produced by these cells and may also play a role in clinging to some substances to support abalones in addition to the main functions of lubrication and protection.

• Food Science of Animal Resources
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• v.35 no.4
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• pp.572-576
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• 2015

The most commonly used infant formulas contain lactose originating from cow milk. Goat milk has recently been claimed to be nutritionally more effective for infants than other milks. In baby foods, much emphasis is placed on the concentrations of intestinal microflora-promoting oligosaccharides, which are generally transferred into lactose from milk during crystallization process. Here we show that higher level of free sialic acid is present in goat lactose powder compared to cow lactose powder. Without proteinase K treatment, the amount of 3-sialyllactose and 6-sialyllactose were similar in goat and cow lactose powders. However, after proteolysis, 6-sialyllactose was present at higher levels in goat than in cow lactose powder. Galactooligosaccharides, a group of prebiotics, are present in milk in the form of glycoproteins. Galactooligosaccharide content was also higher in goat lactose powder than in cow lactose powder.

• YAKHAK HOEJI
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• v.51 no.4
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• pp.259-263
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• 2007

We previously reported the isolation of a sialic acid-specific lectin eluted from the bark of Maackia fauriei using alkaline buffer on a fetuin-affinity column. Application of a borate-based elution buffer in the present study increased the specific activity of purified lectin from crude protein extract by 2.6-fold, whilst only slightly decreasing the recovery by 1.13%. The biological properties of the lectin eluted with borate buffer were the same as those of the lectin eluted with alkaline buffer such as in terms of the hemagglutination activity, hemagglutination inhibition activity, molecular mass, purity, and cytotoxicity to human breast cancer cells. A prepared biotin-labeled lectin conjugate was used to investigate the binding to various glycoproteins. Our results indicate that eluting with borate buffer is more efficient than using alkaline buffer to isolate the lectin adsorbed in a fetuin-affinity column.

• Molecules and Cells
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• v.25 no.1
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• pp.99-104
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• 2008

Gangliosides, sialic acid-containing glycosphingolipids, are implicated in many neuronal diseases, but the precise molecular mechanisms underlying their pathological activities are poorly understood. Here we report that TLR2 participates in the initiation of ganglioside-triggered inflammatory signaling responses. Using FACS analysis and immunofluorescence microscopy, we found that gangliosides rapidly enhanced the cell surface expression of TLR2 in microglia, while reducing that of TLR4. The ganglioside-dependent increase of TLR2 expression was also observed at the messenger and protein levels. We also showed that gangliosides stimulate the interaction of TLR2 with Myd88, an adaptor for TLRs, and obtained evidence that lipid raft formation is closely associated with the ganglioside-induced activation of TLR2 and subsequent inflammatory signaling. These results collectively suggest that TLR2 contributes to the ability of gangliosides to cause inflammatory conditions in the brain.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.844-851
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• 2004

Efficient mammalian erythropoietin (EPO)-expression systems are required for therapeutic applications. The accumulation of ammonia is a major problem in the production of recombinant proteins in cultured animal cells. To counter this problem we introduced the first two genes of the urea cycle, carbamoyl phosphate synthetase (CPSI) and ornithine transcarbamylase (OTC), into IBE Chinese Hamster Ovary (CHO) cells by stable transfection. The resulting cell line, CO5, had a higher growth rate and accumulated less ammonia per cell than the parental cell line, IBE. In addition, it produced 2 times more EPO than the parent, and the purified EPO contained a higher proportion of acidic isoforms with approximately 15% more sialic acid.

• Molecules and Cells
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• v.20 no.3
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• pp.354-360
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• 2005

Neuronal damage subsequent to transient cerebral ischemia is a multifactorial process involving several overlapping mechanisms. Gangliosides, sialic acid-conjugated glycosphingolipids, reduce the severity of acute brain damage in vitro. However their in vivo effects on the cerebral cortex damaged by ischemic infarct are unknown. To assess the possible protective role of gangliosides we examined their expression in the cerebral cortex damaged by ischemic infarct in the rat. Ischemia was induced by middle cerebral artery (MCA) occlusion, and the resulting damage was observed by staining with 2, 3, 5-triphenylterazolium chloride (TTC). High-performance thin-layer chromatography (HPTLC) showed that gangliosides GM3 and GM1 increased in the damaged cerebral cortex, and immunofluorescence microscopy also revealed a significant change in expression of GM1. In addition, in situ hybridization demonstrated an increase in the mRNA for ganglioside GM3 synthase. These results suggest that gangliosides GM1 and GM3 may be synthesized in vivo to protect the cerebral cortex from ischemic damage.

• YAKHAK HOEJI
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• v.49 no.1
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• pp.6-10
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• 2005

Immunoglobulin Y (IgY) obtained from chicken as the immunization host brings several advantages to antibody production, such as improved yield, lower cost, longer stability and higher specificity than mammalian immunoglobulin. In the present study, we attempted to produce IgY against a sialic acid-binding lectin, Maackia fauriei agglutinin (MFA), from egg yolk of white Leghorn hens. For the isolation of IgY from egg yolk, we applied a water dilution method. The weekly yield of IgY was determined by enzyme-linked immunosorbent assay, with a final yield of anti-MFA IgY from total IgY of approximately $1\%$. The yielded IgY were used to prepare IgY-affinity column conjugated with CNBr-activated Sepharose 4B, which resulted in the lectin being successfully purified in a single step from Maackia fauriei. This purified lectin exhibited the same hemagglutination activity as lectin purified using conventional purification methods.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.864-869
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• 1995

Investigation of the structures of the gangliosides has proven to be very important in the understanding of their biological roles such as regulation of differentiation and growth of cells. We used nuclear magnetic resonance spectros-copy in order to investigate the structure of GA1. In order to do this, the assignment of spectra is a prerequisite. Since GA1 does not have polar sialic acid, the spectral overlap is severe. In order to solve this problem, we use 2D NMR spectroscopy and heteronuclear 1H/13C correlated spectroscopy in this study. Here, we report the complete assignment of the proton and the carbon spectra of the GA1 in DMSO-d6-D20 (98:2, v/v). These assignments will be useful for interpreting 1H and 13C NMR data from uncharacterized oligosaccharides and for determining the linkage position, the number of sugar rings, and the sequence of new ganglioside. Amide proton in ring Ⅲ shows many interring nOes and has intramolecular hydrogen bonding. This appears to be an important factor in tertiary folding of GA1. Based on this assignment, determination of three dimensional structure of GA1 will be carried out. Studies on the conformational properties of GA1 may lead to a better understanding of the molecular basis of its functions.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.569-575
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• 1998

Investigation of the structure of the gangliosides has proven to be very important in the understanding of their biological roles. We have determined the tertiary structure of asialoganglioside GM1 $(GA_1)$ using NMR spectroscopy and distance geometry calculations. All of the structures are very similar except the glycosidic torsion angles in the ring IV and ring III linkages. There are two low-energy structures for GA1, G1 and G2. G1 differs from G2 only in the IV-III glycosidic linkages and the orientation of acetamido group in ring III. There is a stable intramolecular hydrogen bond between the third hydroxyl group in ring I and the ring oxygen atom in ring II. Also, there may be a weak hydrogen bond between the second hydroxyl group in ring IV and the acetamido group in ring III. Small coupling constants of $^3J_{IH3,IOH3}\; and\; ^3J_{IVH2,IVOH2}$ support this result. Overall structural features of $(GA_1)$ are very similar to those of $(GM_1)$. It implicates that specificities of the sugar moieties in GM1 are caused not by their tertiary foldings, but mainly by the electrostatic interactions between the polar sialic acid and its receptors. Since it is evident that $(GA_1)$ is more hydrophobic than $(GA_1)$, a receptor with a hydrophobic binding site can recognize the $(GA_1)$ better than $(GA_1)$. Studies on the conformational properties of $(GA_1)$ may lead to a better understanding of the molecular basis of its functions.