Biomedical subjects

Se-Kwon Kim

Publications and source records attributed to Se-Kwon Kim.

At least 37 records · Page 2Linked to original sources

PubMed2006

Fish-bone peptide increases calcium solubility and bioavailability in ovariectomised rats.

Fish-bone peptides (FBP) with a high affinity to Ca were isolated using hydroxyapatite affinity chromatography, and FBP II with a high ratio of phosphopeptide was fractionated in the range of molecular weight 5.0-1.0 kDa by ultramembrane filtration. In vitro study elucidated that FBP II could inhibit the formation of insoluble Ca salts in neutral pH. In vivo effects of FBP II on Ca bioavailability were further examined in the ovariectomised rat. During the experimental period, Ca retention was increased and loss of bone mineral was decreased by FBP II supplementation in ovariectomised rats. After the low-Ca diet, the FBP II diet, including both normal level of Ca and vitamin D, significantly decreased Ca loss in faeces and increased Ca retention compared with the control diet. The levels of femoral total Ca, bone mineral density, and strength were also significantly increased by the FBP II diet to levels similar to those of the casein phosphopeptide diet group (no difference; P>0.05). In the present study, the results proved the beneficial effects of fish-meal in preventing Ca deficiency due to increased Ca bioavailability by FBP intake.

Absorption↗

PubMed2005

Strong electronic charge as an important factor for anticancer activity of chitooligosaccharides (COS).

Even though several studies report the importance of chitosan derivatives for their anticancer activity, no clear information is available to describe the relationship between their charge properties and observed activities. In this research, differently charged chitooligosaccharide (COS) derivatives were synthesized and their anticancer activities were studied using three cancer cell lines, HeLa, Hep3B and SW480. Neutral red and MTT cell viability studies revealed that, highly charged COS derivatives could significantly reduce cancer cell viability, regardless to the positive or negative charge. Further, fluorescence microscopic observations and DNA fragmentation studies confirmed that the anticancer effect of these highly charged COS derivatives were due to necrosis. However, the exact molecular mechanism for anticancer activity of strongly charged COS compared to their poorly charged counterparts is not clear.

Acridine Orange↗

PubMed2005

Antimicrobial action of novel chitin derivative.

Aminoethyl-chitin (AEC) was synthesized in an attempt to both increase solubility of chitin in water and biological activity. AEC was obtained by grafting 2-chloroethylamino hydrochloride onto chitin at C-6 position. The structure of AEC was elucidated FT-IR and (1)H NMR spectroscopy, and its antimicrobial activity was investigated using three Gram-positive and Gram-negative bacteria. The integrity of the cell membranes of the representatives E. coli and S. aureus was investigated by determining the release of intracellular components of cells. When treated with AEC, release of 260 nm absorbing materials quickly increased both E. coli and S. aureus, but absorbance value was different due to the difference in cell structures. For detailed study, outer membrane (OM) and inner membrane (IM) permeabilization assay were performed using the fluorescent probe 1-N-phenylnaphthylamine (NPN) and the release of cytoplasmic beta-galactosidase activity. The results showed that AEC rapidly increased NPN uptake and the release of cytoplasmic beta-galactosidase via increasing the permeability of OM and IM. In addition, cytotoxic effect of AEC was assessed using human lung fibroblast (MRC-5) cell line, and AEC showed less toxic against MRC-5.

Anti-Infective Agents↗

PubMed2005

Investigation of jumbo squid (Dosidicus gigas) skin gelatin peptides for their in vitro antioxidant effects.

Peptides derived from tryptic hydrolysate of jumbo squid (Dosidicus gigas) skin gelatin were assessed for their antioxidant properties in different in vitro assay systems. The hydrolysate itself exhibited a strong lipid peroxidation inhibition and it was much higher than that of natural antioxidant, alpha-tocopherol. In addition, it could scavenge highly active free radicals in oxidative systems, in the order of hydroxyl and carbon-centered radicals. Two representative peptides with comparatively higher antioxidant potency were purified and characterized as Phe-Asp-Ser-Gly-Pro-Ala-Gly-Val-Leu (880.18 Da) and Asn-Gly-Pro-Leu-Gln-Ala-Gly-Gln-Pro-Gly-Glu-Arg (1241.59 Da). Furthermore, viability of radical-mediated oxidation-induced human lung fibroblasts was enhanced following the treatment of two peptides. However it did not exhibit substantial ion chelation, and we presumed that the observed radical scavenging potency of these peptides play a vital role for their strong antioxidant activity. Based on our results we suggest that hydrophobic amino acids present in peptide sequences contributed greatly for observed antioxidant activities.

Animals↗

PubMed2005

Effect of chitooligosaccharides on calcium bioavailability and bone strength in ovariectomized rats.

Chitosan polymer with deacetylation degree of 93% was hydrolyzed with an endo-type chitosanase (35,000 U/g protein) with substrate to enzyme ratio of 1 to 1.5 for 18 h in a batch reactor, and then the resultant hydrolysates were fractionated into four different molecular weights using an ultrafiltration (UF) membrane reactor system. An in vitro study elucidated that four kinds of chitooligosaccharides (COSs) could efficiently inhibit the formation of insoluble calcium salts in the neutral pH. In vivo effects of COSs on Ca bioavailability were further studied in the osteoporosis modeling rats induced by ovariectomy and concurrent low calcium intake. During the experimental period corresponding to the menopause with the osteoporosis disease, calcium retention was increased and bone turnover was decreased by COS IV supplementation in the ovariectomized (OVX) rats. After the low Ca diet, COS IV diet including both normal level of calcium and vitamin D significantly decreased calcium loss in feces and increased calcium retention compared to the control diet. The levels of femoral total calcium, bone mineral density (BMD), and femoral strength were also significantly increased by the COS IV diet in a similar level to those of CPP diet group. In the present study, the results proved the beneficial effects of low molecular chitooligosaccharide (COS IV) in preventing negative mineral balance.

Animals↗

PubMed2005

Reactive oxygen scavenging effect of enzymatic extracts from Sargassum thunbergii.

The free radical scavenging activity of water soluble natural antioxidants from Sargassum thunbergii, which is a brown marine alga, was evaluated by examining the radical scavenging activities of the extracts of hydrolyzates from S. thunbergii on hydroxyl, 1,1-diphenyl-2-picrylhydrazyl (DPPH), and alkyl radicals. A spin-trapping electron spin resonance (ESR) spectrometer was employed, and the results were compared for their ESR signal intensity. S. thunbergii was enzymatically hydrolyzed to prepare water soluble extracts by five carbohydrases (AMG, Celluclast, Termamyl, Ultraflo, and Viscozyme) and proteases (Alcalase, Flavorzyme, Kojizyme, Neutrase, and Protamex). The scavenging activity of the radicals increased with increased concentrations of the extracts. The scavenging results were higher for hydroxyl and alkyl radicals and lower for DPPH radical as compared with vitamin C as a reference. The hydrogen peroxide scavenging activity of the extracts was also investigated; the Alcalase extract showed the highest scavenging activity among the extracts prepared with the five proteases and five carbohydrates. In addition, the DNA damage was determined by using the comet assay with alkaline electrophoresis and was quantified by measuring the tail length. The preventive effect of Alcalase extract from S. thunbergii against DNA damage increased with increments of concentration of the enzymatic extracts.

DNA Damage↗

PubMed2005

Water-soluble chitosan derivatives as a BACE1 inhibitor.

BACE1 (the beta-site APP-cleaving enzyme) inhibitory activities of water-soluble chitosan derivatives substituted with aminoethyl, dimethylaminoethyl and diethylaminoethyl groups were investigated. AE-chitosan (90%) prepared from 90% deacetylated chitosan showed the strongest BACE1 inhibitory activity than those of other derivatives. The inhibitory pattern was found to be non-competitive by Dixon plot, and the value of the inhibition constant (K(i)) was 85 microg/mL.

Amyloid Precursor Protein Secretases↗

PubMed2005

Improvement of ACE inhibitory activity of chitooligosaccharides (COS) by carboxyl modification.

In the present research, chitooligosaccharides (COS) were carboxylated with -COCH(2)CH(2)COO(-) groups to obtain specific structural features similar to Captopril. Angiotensin I converting enzyme (ACE) inhibitory activity of carboxylated COS was studied and observed to enhance its activity with increased substitution degree. Further, Lineweaver-Burk plot analysis revealed that inhibition was competitive via obligatory binding site of the enzyme. This was accompanied with substitution of positively charged quarternized amino groups to COS with different substitution degrees, in which negative impact on ACE inhibition was observed.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2005

A novel anticoagulant purified from fish protein hydrolysate inhibits factor XIIa and platelet aggregation.

A novel fish protein having anticoagulant and antiplatelet properties was enzymatically extracted from the marine fish, yellowfin sole (Limanda aspera) and purified to homogeneity producing an overall purification fold of 206.6. MALDI-TOF mass spectroscopic and SDS-PAGE analysis identified the purified protein as 12.01 kDa single-chain monomeric protein. It inhibited the activated coagulation factor XII (FXIIa) by forming an inactive complex regardless of Zn2+ mediation, and was named, yellowfin sole anticoagulant protein (YAP). In addition, YAP act to antagonize platelet membrane glycoprotein integrin, to arrest platelet aggregation. However, YAP was not able to block the adhesion of platelets to collagen, which mediate via major collagen receptors, GPIa/IIa on platelet membrane. Furthermore, YAP did not possess plasminogen activator-like activity to activate fibrinolysis. In fact, our findings indicate that YAP binds with FXIIa and platelet membrane integrins to inhibit thrombosis in vitro.

Animals↗

PubMed2005

Antioxidant properties of a radical-scavenging peptide purified from enzymatically prepared fish skin gelatin hydrolysate.

Hoki (Johnius belengerii) skin gelatin was hydrolyzed with three commercial enzymes to identify radical-scavenging potencies of derived peptides. Peptides derived from tryptic hydrolysate exhibited the highest scavenging activities on superoxide, carbon-centered 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals assessed by ESR spectroscopy. Following consecutive chromatographic separations of tryptic hydroolysate, the peptide sequence His-Gly-Pro-Leu-Gly-Pro-Leu (797 Da) acted as a strong radical scavenger under studied conditions. Further, this peptide could act as an antioxidant against linoleic acid peroxidation and the activity was closer to the highly active synthetic antioxidant butylated hydroxytoluene (BHT). In addition, antioxidative enzyme levels in cultured human hepatoma cells were increased in the presence of this peptide and it was presumed to be the peptide involved in maintaining the redox balance in the cell environment. Present data indicate that free-radical-scavenging activities of hoki skin gelatin peptides substantially contribute to their antioxidant properties measured in different oxidative systems.

Amino Acid Sequence↗

PubMed2005

Angiotensin I converting enzyme (ACE) inhibitory peptide derived from the sauce of fermented blue mussel, Mytilus edulis.

The angiotensin I converting enzyme (ACE) inhibitory activity of fermented blue mussel sauce (FBMS) was investigated. Blue mussels were fermented with 25% NaCl (w/w) at 20 degrees C for 6 months and the resultant mixture was passed through a 40-mesh sieve, desalted using an electrodialyzer and then lyophilized. The IC(50) value of FBMS for ACE activity was 1.01 mg/ml. An ACE inhibitory peptide was purified from FBMS using Sephadex G-75 gel chromatography, SP-Sephadex C-25 ion exchange chromatography and reversed-phase high-performance liquid chromatography on a C(18) column. The IC(50) value of purified ACE inhibitory peptide was 19.34 microg/ml, and 10 amino acid residues of the N-terminal sequence was EVMAGNLYPG. The purified peptide was evaluated for antihypertensive effect in spontaneously hypertensive rats (SHR) following oral administration. Blood pressure significantly decreased after peptide ingestion. This result suggested that FBMS may have beneficial effects on hypertension.

Amino Acid Sequence↗

PubMed2005

Factors affecting the free radical scavenging behavior of chitosan sulfate.

Scavenging activity of hydroxyethyl chitosan sulfate (HCS) against 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl and carbon-centered radical species were studied using electron spin resonance (ESR) spectroscopy. In addition, its antioxidant activity to retard lipid peroxidation was also evaluated in a linoleic acid model system. HCS could scavenge DPPH (33.78%, 2.5 mg/mL) and carbon-centered radicals (67.74%, 0.25 mg/mL) effectively. However, chitosan sulfate did not exhibit any scavenging activity against hydroxyl radicals, but increased its generation. This was different from the published literature and was presumed due to the loss of chelating ability on Fe2+. This assumption could further confirm from the results obtained for Fe2+-ferrozine method that upon sulfation chitooligosaccharides lost its chelation properties. Therefore, HCS can be identified as antioxidant that effectively scavenges carbon centered radicals to retard lipid peroxidation.

Antioxidants↗

PubMed2005

Purification and in vitro antioxidative effects of giant squid muscle peptides on free radical-mediated oxidative systems.

Low molecular weight peptides obtained from ultrafiltration (UF) of giant squid (Dosidicus gigas) muscle protein were studied for their antioxidative effects in different in vitro oxidative systems. The most potent two peptides, Asn-Ala-Asp-Phe-Gly-Leu-Asn-Gly-Leu-Glu-Gly-Leu-Ala (1307 Da) and Asn-Gly-Leu-Glu-Gly-Leu-Lys (747 Da), exhibited their antioxidant potential to act as chain-breaking antioxidants by inhibiting radical-mediated peroxidation of linoleic acid, and their activities were closer to highly active synthetic antioxidant, butylated hydroxytoluene. Addition of these peptides could enhance the viability of cytotoxic embryonic lung fibroblasts significantly (P<.05) at a low concentration of 50 microg/ml, and it was presumed due to the suppression of radical-induced oxidation of membrane lipids. Electron spin trapping studies revealed that the peptides were potent scavengers of free radicals in the order of carbon-centered (IC(50) 396.04 and 304.67 microM), hydroxyl (IC(50) 497.32 and 428.54 microM) and superoxide radicals (IC(50) 669.34 and 573.83 microM). Even though the exact molecular mechanism for scavenging of free radicals was unclear, unusually high hydrophobic amino acid composition (more than 75%) of giant squid muscle peptides was presumed to be involved in the observed activities.

Animals↗

PubMed2005

Myrothenones A and B, cyclopentenone derivatives with tyrosinase inhibitory activity from the marine-derived fungus Myrothecium sp.

New 3-amino-5-ethenylcyclopentenones, myrothenones A (4) and B (5), were isolated together with known 6-n-pentyl-alpha-pyrone (1), trichodenone A (2), and cyclonerodiol (3) from the marine algicolous fungus of genus of Myrothecium. The structure and absolute stereochemistry of the new compounds were established by spectral interpretation and X-ray analysis. Compounds 1 and 4 exhibited a tyrosinase inhibitory activity with IC(50) value of 0.8 and 6.6 muM, respectively, which are more active than kojic acid (IC(50), 7.7 muM) currently being used as a functional personal-care compound.

Ascomycota↗

PubMed2005

Selective cadmium accumulation using recombinant Escherichia coli.

Recombinant Escherichia coli JM109 (pZH3-5/pMT), harboring a manganese transport gene (mntA) and a metal-sequestering protein (metallothionein [MT]) gene, was cultivated to accumulate cadmium (Cd) in an aqueous phase. Isopropyl beta-D-thiogalactoside (IPTG)-induced cells showed rapid Cd(2+) ion accumulation (90% of maximum accumulation in 15 min) and had an accumulation six times higher than that of the control. Under optimum conditions, i.e., pH 7, 37 degrees C and 0.5 (OD600), 1.5 mM IPTG induction resulted in the accumulation of 21.5 micromol Cd/g dry cell. Storage at 37 degrees C for 24 h had no effect on the accumulation. Significantly, Cd was selectively accumulated in a solution containing an equal concentration of three other metals, resulting in more than 90% of the total accumulated metals being Cd. The accumulation of Cd was reduced by the presence of Mn2+ ion whereas no significant effect was observed with Cu2+, Zn2+ and Pb2+ ions. A chelator, EDTA, had no effect on the accumulation up to 100 mM. The bioaccumulation rate followed Michaelis-Menten kinetics (Vm=2.7 micromol Cd2+/min.g dry cell, Km=0.67 microM). The equilibrium isotherm showed a Langmuir isotherm. In the membrane reactor experiment, 1 mg/l Cd in an inlet solution decreased to 0.2 mg/l in the effluent, removing 80% of Cd, continuously. These results indicated the potentials of a genetically modified microorganism for the highly selective accumulation of Cd at a low concentration and the future application to the removal and recovery of Cd.

Bacterial Proteins↗

PubMed2004

A novel angiotensin I converting enzyme inhibitory peptide from Alaska pollack (Theragra chalcogramma) frame protein hydrolysate.

Alaska pollack frame protein, which is normally discarded as an industrial byproduct in the processing of fish in plants, was hydrolyzed with pepsin. This was fractionated into five major types of Alaska pollack frame protein hydrolysates (APH-I, 10-30 kDa; APH-II, 5-10 kDa; APH-III, 3-5 kDa; APH-IV, 1-3 kDa; and APH-V, below 1 kDa) using an ultrafiltration membrane bioreactor system. Angiotensin I converting enzyme (ACE) inhibitory activities of the fractionated hydrolysates were investigated, and the fraction that exhibited the highest ACE inhibitory activity was further purified using consecutive chromatographic methods on SP-Sephadex C-25 column, Sephadex G-25 column, and high-performance liquid chromatography (HPLC) on an octadecylsilane column. Finally, we purified a novel ACE inhibitory peptide with an IC50 value of 14.7 microM, and the sequence of the peptide was Phe-Gly-Ala-Ser-Thr-Arg-Gly-Ala. In addition, the ACE inhibition pattern of the peptide was found to be noncompetitive.

Amino Acid Sequence↗

PubMed2004

Early gene expression analyzed by cDNA microarray and RT-PCR in osteoblasts cultured with water-soluble and low molecular chitooligosaccharide.

Chitosan has a variety of biological activities. However, little is known about how chitosan modulates the hard tissue forming cells. When we cultured an osteoblastic cell line in alpha-MEM supplemented with 10% FBS and 0.005% chitooligosaccharide for 3 days, alkaline phosphatase (ALP) activity was significantly high compared with the control culture group (p<0.05). This study was focused on gene expression in osteoblasts cultured with water-soluble chitooligosaccharide. cDNA probes were synthesized from isolated RNA and labeled with fluorescent dye. They were hybridized with Human 1.0((R)) cDNA microarray, and fluorescent signal was analyzed. cDNA microarray analysis revealed that 16 genes were expressed at >/=1.5-fold higher signal ratio levels in the experimental group compared with the control group after 3 days. RT-PCR analysis showed that chitosan oligomer induced an increase in the expression of two genes, CD56 antigen and tissue-type plasminogen activator. Furthermore, the expression of mRNAs for BMP-2 was almost identical in the experimental and control groups after 3 days of culture, but slightly increased after 7 days of culture with chitosan oligomer. These results suggest that a super-low concentration of chitooligosaccharide could modulate the activity of osteoblastic cells through mRNA levels and that the genes concerning cell proliferation and differentiation can be controlled by water-soluble chitosan.

Bone Morphogenetic Protein 2↗

PubMed2004

Free radical scavenging properties of hetero-chitooligosaccharides using an ESR spectroscopy.

Nine kinds of hetero-chitooligosaccharides (hetero-COSs) with relatively higher molecular weights (90, 75 and 50-HMWCOS), medium molecular weights (90, 75 and 50-MMWCOS), and lower molecular weights (90, 75 and 50-LMWCOS) were prepared from partially deacetylated hetero-chitosans (90, 75 and 50% deacetylated chitosan), and their scavenging activities were investigated against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, superoxide and carbon-centered radicals using electron spin resonance (ESR) spin-trapping technique. Superoxide, hydroxyl and carbon-centered radicals were generated from hypoxanthine-xanthine oxidase reaction, hydrogen peroxide-ferrous sulfate (Fenton reaction) and azo compound 2,2-azobis-(2-amidinopropane)-hydrochloride (AAPH), respectively. The ESR results revealed that 90-MMWCOS, which is having relatively medium molecular weights prepared from 90% deacetylated chitosan, showed the highest scavenging activity on all tested radicals. In addition, the radical scavenging activity of hetero-COSs increased with a dose-dependent manner, and it was dependent on their degree of deacetylation values and molecular weights.

Acetylation↗