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S I Kwon

Publications and source records attributed to S I Kwon.

7 recordsLinked to original sources

Catalase activities of Phanerochaete chrysosporium are not coordinately produced with ligninolytic metabolism: catalases from a white-rot fungus.

Phanerochaete chrysosporium uses hydrogen peroxide as a substrate in its ligninolytic phase. To determine how the fungus protects itself against detrimental effects of reactive oxygen species, catalase activity was examined. The fungus produced up to four different catalase isozymes, Cat A to D. Isozyme CatC was the dominant activity in all growth conditions. A minor catalase, CatD, was apparent in low-carbon culture and upon exposure of mycelium grown on high-nitrogen medium with 5-50 mm of hydrogen peroxide. In low-nitrogen culture, an increase in catalase-specific activity preceded the onset of ligninolysis by 3 days. In low-carbon culture, catalase was produced at an even higher level without development of ligninolysis. Thus, catalase activity was not coordinately produced with ligninolytic metabolism.

Catalase↗

Differentiation between reinfection and recrudescence of helicobacter pylori strains using PCR-based restriction fragment length polymorphism analysis.

The aim of this study was to evaluate whether PCR-based restriction fragment length polymorphism (RFLP) analysis was effective in differentiating between reinfection and recrudescence of H. pylori strains. Following a 1-2 week regimen of omeprazole 20 mg, amoxicillin 1.0 g, and clarithromycin 500 mg twice daily, twenty patients with duodenal ulcer were enrolled in the study. Ten patients (group 1, control) were not successfully treated, and another 10 patients (group 2) exhibited recurrence of infection 6-24 months following the therapy. Follow-up diagnosis was performed by Giemsa stain and CLO test. RFLP profiles of antral and midbody biopsy specimens were compared before and after therapy. PCR products using the ureC gene were digested with restriction enzymes Hha I, Mbo I, and Hind III, and the fragments generated were analyzed by agarose gel electrophoresis. Hha I, Mbo I, and Hind III digestion produced 13, 7, and 2 distinguishable digestion patterns, respectively. There was no difference in RFLP profiles seen before and after the therapy in 17 duodenal ulcer patients, while different RFLP profiles were discovered in 3 patients. Following treatment, one (group 2) patient differed in Mbo I, and two (one each from both groups) patients differed in Hha I and Mbo I RFLP patterns. Eight of group 2 patients showed recrudescence of previous infection and two patients had reinfection by another strain. This study supports the hypothesis that PCR-based RFLP analysis can be effective for differentiating reinfection and recrudescence of H. pylori strains following triple therapy.

Adult↗

Analysis of Plasmodium vivax merozoite surface protein-1 gene sequences from resurgent Korean isolates.

The merozoite surface protein-1 (MSP-1) of Plasmodium vivax exhibits great antigenic diversity among different isolates of this parasite. This antigen is a useful genetic marker for studying the polymorphism of natural P. vivax parasite populations. One or more of these populations has been responsible for resurgent malaria now occurring in Korea. This paper reports the analysis of a highly polymorphic region between interspecies conserved blocks 5 and 6 of the MSP-1 gene, using the polymerase chain reaction to amplify the DNA fragment encompassing these regions from 25 Korean isolates, followed by sequencing. Almost all amino acid sequences of Korean isolates were nearly identical to that of Thai isolates TD525A (96.6-99.7%) and TD424 (96.3-99.5%), and very similar to that of the France-Belem strain when compared with other isolates (Sal-1, Sri Lanka, and Colombia). Interallelic recombination was found in the poly-Q repeat and a Sal-1 type amino acid structure was observed in all isolates. This study shows that the MSP gene nucleotide sequence of resurgent P. vivax in Korea is most similar to that of Thai isolates; however, the Korean strains are phylogenetically unique.

Amino Acid Sequence↗

Isolation and characterization of mitochondrial manganese superoxide dismutase (MnSOD) from Capsicum annuum L.

A cDNA clone for a mitochondrial manganese superoxide dismutase (MnSOD) was isolated and characterized from red pepper (Capsicum annuum L.). The clone consisted of 941 bp containing one open reading frame (ORF) of 687 bp, 34 bp/220 bp of 5'/3'-untranslated region. Amino acid sequence of the ORF showed the highest homology (86%) with that of Nicotiana plumbaginifolia. It encodes for a polypeptide of 228 amino acids with a molecular mass of 25.5 kDa and a pI value of 8.39. Genomic Southern hybridization suggested that more than one copy are present. Northern hybridization showed that the MnSOD transcript was more abundant in stems than in leaves and roots. When seedlings were treated with arsenate (0.1-10 mM), the MnSOD transcript level increased slightly at 0.1 mM and then dropped, while the Cu/ZnSOD transcript level increased at 1 mM, and also dropped at higher concentrations.

Amino Acid Sequence↗

Isolation and characterization of the catalase gene from Rhizobium sp. SNU003, a root nodule symbiont of Canavalia lineata.

A catalase gene from Rhizobium sp. SNU003, a root nodule symbiont of Canavalia lineata, was cloned and its nucleotide sequence was determined. The Rhizobium DNA of about 280 bp was amplified using two PCR primers synthesized from the conserved sequences of the type I catalase gene. The nucleotide sequence of the amplified fragment revealed three regions that were conserved in the catalase, showing it as being part of the catalase gene. A genomic Southern hybridization using this fragment as a probe showed that the 5.5 kb PstI, 1.8 kb EcoRI, and 0.7 kb StyI fragments hybridized strongly with the probe. The Rhizobium genomic library constructed into the EMBL3 vector was screened, and one catalase clone was selected. The nucleotide sequence of the 5.5 kb PstI fragment from the clone revealed an open reading frame of 1455 bp, encoding a polypeptide of 485 amino acids with a molecular mass of 54,958 Da and a pI of 6.54. The predicted amino acid sequence of the catalase is 66.3% identical to that of Bacteroides fragilis, but was only 53.3% identical to the Rhizobium meliloti catalase.

Amino Acid Sequence↗

Isolation and characterization of cytosolic copper/zinc superoxide dismutase from Capsicum annuum L.

A cDNA clone for a cytosolic Cu/Zn superoxide dismutase (Cu/ZnSOD) was isolated and characterized from red pepper (Capsicum annuum L.). The clone consisted of 735 bp containing one open reading frame (ORF) of 459 bp, 46 bp of 5'- and 230 bp of 3'-untranslated region. The nucleotide sequence of the ORF showed 93% homology with that of Nicotiana plumbaginifolia and tomato. It encodes a polypeptide of 154 amino acids with a molecular weight of 15,300. Genomic Southern hybridization suggested that only one copy is present. During cold treatment at 4 degrees C, its expression was maintained at a similar level regardless of illumination.

Amino Acid Sequence↗