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Biomedical subjects

M H Park

Publications and source records attributed to M H Park.

At least 19 recordsLinked to original sources
PubMed1999

Identification of lysine350 of yeast deoxyhypusine synthase as the site of enzyme intermediate formation.

The posttranslational formation of deoxyhypusine in the precursor of eukaryotic initiation factor 5A (eIF5A) is catalysed by deoxyhypusine synthase. This NAD-dependent reaction involves transfer of the 4-aminobutyl moiety of spermidine to a single lysine residue in the eIF5A precursor. The present study shows evidence for the formation of a covalent enzyme-substrate intermediate between a specific lysine residue (Lys350) of yeast deoxyhypusine synthase and the 4-aminobutyl moiety from spermidine. Substitution of this lysine residue with Arg or Ala totally prevented the formation of the enzyme intermediate and consequently precluded deoxyhypusine synthesis in the eIF5A precursor, leading to the conclusion that the enzyme intermediate formed at Lys350 is critical for deoxyhypusine synthesis activity. The results provide a rational basis for the inability of the mutated deoxyhypusine synthase gene encoding arginine in place of Lys350 to support growth in yeast (Park et al., 1998). The demonstration of the formation of an enzyme-imine intermediate in yeast deoxyhypusine synthase analogous to that of the human enzyme strongly suggest that the enzyme mechanism is conserved in diverse eukaryotes.

Amino Acid Sequence↗
PubMed1999

Association of HLA class I antigens with diffuse panbronchiolitis in Korean patients.

Diffuse panbronchiolitis (DPB) is a chronic obstructive pulmonary disease of unknown etiology. Observations of significantly increased frequency of human leukocyte antigen (HLA)-B54 in Japanese patients and occurrence of familial cases suggest possible genetic predisposition to the disease susceptibility. To evaluate the possible association of HLA with the disease in Koreans, we have analyzed 30 patients for HLA class I (A, B, C) and class II (DR) antigens by the serologic and DNA typing methods, respectively. The most significant change in the patients compared to the control subjects was increased frequency of HLA-A11 (53.3% versus 17.5%, corrected p [pc] = 1.2 x 10(-)4, odds ratio [OR] = 5.4). In addition, B55 showed significant positive association (16.7% versus 3.5%, pc = 0.05, OR = 5.5), and B62 and Cw4 showed rather weak association with the disease. Certain A11-associated haplotypes showed much stronger positive association with the disease, compared to A11 antigen itself. Observations of a strong association of HLA-A11 in Koreans and B54 in Japanese with DPB suggest that the candidate gene(s) responsible for the disease susceptibility is located within the HLA class I region, most probably between HLA-A and HLA-B loci.

Adult↗
PubMed1999

Symptomatic hypertrophic obstructive cardiomyopathy: the role of dual-chamber pacing.

BACKGROUND AND PURPOSE: The management of symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM) has traditionally consisted of beta blockers and calcium channel blockers. Surgical treatment has been employed for operable patients who became refractory to medical therapy. However, associated complications, mortality rate, and recurrence of functional limitations have shifted the focus toward alternative therapy modalities. Recently, permanent dual-chamber (DDD) pacemaker has been introduced as an alternative treatment option. PATIENTS AND METHODS: This study comprises clinical, angiographic, echocardiographic, and electrophysiologic data obtained at a single center on 10 symptomatic patients with HOCM who received a DDD pacemaker after medical therapy failed to relieve symptoms. Presenting symptoms were exertional dyspnea and chest pain (60%), syncope (20%), and presyncope (20%). These symptoms were documented for 8.9+/-7.1 years before pacemaker implantation. All patients were in New York Heart Association functional class III or IV before pacemaker therapy. RESULTS: Placement of a permanent DDD pacemaker decreased the left ventricular outflow tract gradient from 83+/-44 mm Hg (range: 35-180 mm Hg) to 47.1+/-25.3 mm Hg (range: 10-75 mm Hg) in these patients. Within 1 to 30 months, follow-up found that the functional status of eight out of the 10 patients had improved to New York Heart Association class 0 or I. CONCLUSION: In selected patients with symptomatic HOCM who fail to respond to medical therapy, DDD pacemaker may offer a nonsurgical alternative treatment option. Large-scale multicenter, prospective, randomized trials are needed to establish the role of this modality in the treatment of hypertrophic obstructive cardiomyopathy.

Activities of Daily Living↗
PubMed1999

Flank ulcer in a patient with primary antiphospholipid syndrome.

A 32-year-old woman had a recurrent shallow ulcer on the flank. A biopsy specimen showed thromboses in the dermal vessels and she was found to have circulating antiphospholipid antibody with no associated systemic disease. A clean ulcer developed on the flank of a patient with primary antiphospholipid syndrome is considered to be a rarely encountered/unusual presentation of this syndrome.

Adult↗
PubMed1998

Locoregional response and increased natural killer activity after intratumoral injection of HLA-B7/beta2-microglobulin gene in patients with cancer.

The purpose of this study was to assess the therapeutic potential of injecting the gene for HLA-B7/beta2-microglobulin into the subcutaneous metastatic nodules of patients who are refractory to conventional treatments. The nine patients evaluated were divided into three groups and given escalating doses of DNA (20, 40, and 100 microg of the HLA-B7 plasmid DNA/lipid complex for each group) every 2 weeks. Biopsy specimens from the treated tumor nodules of all nine patients were positive for the presence of DNA and for HLA-B7 mRNA expression. Moreover, in six of the nine patients, immunohistology of tumor biopsy samples revealed the expression of recombinant HLA-B7 protein. Also, all nine patients showed an increase in NK activity in their circulating peripheral blood lymphocytes. In two lung cancer patients, one partial and one mixed response was observed after gene transfer. These responses were confined to the treated nodules and the untreated locoregional lymph nodes; the lung masses showed no regression. Remission durations were 14 and 6 weeks, respectively, and in a total of 35 cycles no significant toxicities were observed. Immunohistologic analysis revealed an increased infiltration of CD4+ T cells, macrophages, and NK cells after therapy. In two responding cases, direct intratumoral injection of an allogeneic class I gene could elicit an antitumor response in locoregional areas, possibly through the activation of NK cells.

Adult↗
PubMed1998

Deoxyhypusine synthase activity is essential for cell viability in the yeast Saccharomyces cerevisiae.

Deoxyhypusine synthase catalyzes the first step in the posttranslational synthesis of an unusual amino acid, hypusine (N epsilon-(4-amino-2-hydroxybutyl)lysine), in the eukaryotic translation initiation factor 5A (eIF-5A) precursor protein. The null mutation in the single copy gene, yDHS, encoding deoxyhypusine synthase results in the loss of viability in the yeast Saccharomyces cerevisiae. Upon depletion of deoxyhypusine synthase, and consequently of eIF-5A, cessation of growth was accompanied by a marked enlargement of cells, suggesting a defect in cell cycle progression or in cell division. Two residues of the yeast enzyme, Lys308 and Lys350, corresponding to Lys287 and Lys329, respectively, known to be critical for the activity of the human enzyme, were targeted for site-directed mutagenesis. The chromosomal ydhs null mutation was complemented by the plasmid-borne yDHS wild-type gene, but not by mutated genes encoding inactive proteins, including that with Lys350-->Arg substitution or with substitutions at both Lys308 and Lys350. The mutated gene ydhs (K308R) encoding a protein with diminished activities (< 1% of wild type) could support growth but only to a very limited extent. These findings provide strong evidence that the hypusine modification is indeed essential for the survival of S. cerevisiae and imply a vital function for eIF-5A in all eukaryotes.

Alleles↗
PubMed1998

Crystal structure of the NAD complex of human deoxyhypusine synthase: an enzyme with a ball-and-chain mechanism for blocking the active site.

BACKGROUND: Eukaryotic initiation factor 5A (elF-5A) contains an unusual amino acid, hypusine [N epsilon-(4-aminobutyl-2-hydroxy)lysine]. The first step in the post-translational formation of hypusine is catalysed by the enzyme deoxyhypusine synthase (DHS). The modified version of elF-5A, and DHS, are required for eukaryotic cell proliferation. Knowledge of the three-dimensional structure of this key enzyme should permit the design of specific inhibitors that may be useful as anti-proliferative agents. RESULTS: The crystal structure of human DHS with bound NAD cofactor has been determined and refined at 2.2 A resolution. The enzyme is a tetramer of four identical subunits arranged with 222 symmetry; each subunit contains a nucleotide-binding (or Rossmann) fold. The tetramer comprises two tightly associated dimers and contains four active sites, two in each dimer interface. The catalytic portion of each active site is located in one subunit while the NAD-binding site is located in the other. The entrance to the active-site cavity is blocked by a two-turn alpha helix, part of a third subunit, to which it is joined by an extended loop. CONCLUSIONS: The active site of DHS is a cavity buried below the surface of the enzyme at the interface between two subunits. In the conformation observed here, the substrate-binding site is inaccessible and we propose that the reaction steps carried out by the enzyme must be accompanied by significant conformational changes, the least of which would be the displacement of the two-turn alpha helix.

Binding Sites↗
PubMed1998

Fluoroscopy and selective angiography of left ventricular assist system inflow cannula as a method of detecting cannula entrapment.

Left ventricular assist systems have become an important tool as a bridge to cardiac transplantation. Malfunction of these devices often leads to clinical and hemodynamic deterioration. One potential complication is the obstruction of the inflow cannula secondary to remodeling of the left ventricular cavity. We report two cases where fluoroscopy and selective angiography were used to visualize the orientation and obstruction of the inflow cannula when echocardiographic findings were indeterminant.

Adult↗
PubMed1998

Inhibitory effect of lignans from the rhizomes of Coptis japonica var. dissecta on tumor necrosis factor-alpha production in lipopolysaccharide-stimulated RAW264.7 cells.

The inhibitory effect of 10 lignan constituents isolated from the rhizomes of Coptis japonica var. dissecta on tumor necrosis factor (TNF)-alpha production in lipopolysaccharide (LPS)-stimulated macrophage cell line (RAW264.7 cells) has been studied. Among them, pinoresinol, woorenoside-V and lariciresinol glycoside showed significant inhibitory activities in the range from 37% to 55% at the concentration of 25 micrograms/ml. The results are first report that the lignans isolated from Coptis japonica inhibit TNF-alpha production, and suggest that the lignan components may partly participate in antiinflammatory and antiallergic effect of Coptis japonica through the inhibition of TNF-alpha production.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1998

Isolation and identification of inhibitory compounds on TNF-alpha production from Magnolia fargesii.

Three TNF alpha-inhibitory lignans were isolated from the flower buds of Magnolia fargesii through bioassay-guided isolation. They were identified as eudesmin, magnolin and lirioresinol-B dimethylether on the basis of their spectroscopic data. All three lignans showed inhibitory effects on TNF-alpha production in LPS-stimulated murine macrophage cell line, RAW264.7 and eudesmin showed the strongest activity (IC50 = 51 microM).

Cell Line↗
PubMed1998

A cell surface molecule, JL1; a specific target for diagnosis and treatment of leukemias.

We previously reported a novel differentiation antigen, which is specifically expressed in stage II double positive (CD4+CD8+) human cortical thymocytes (Park et al, J Exp Med 1993; 178: 1447-1451). This study was designed to investigate the expression pattern of JL1 in various types of leukemic cells from patients and normal hematopoietic cells to evaluate the possibility as a tool for diagnosis and treatment of leukemia. The expression of JL1 antigen was observed in 75.6% of leukemic cases (117 out of 154 leukemic patients tested) on flow cytometric analysis. The percentage of JL1-positive cases of T lineage acute lymphoblastic leukemia (T-ALL) (92.6%) was higher than that of other types of leukemias (75%). The presence of JL1 antigen was also confirmed by immunoblotting and immunoprecipitation. Since the JL1 antigen is selectively expressed on the surface of human leukemic cells but not on the mature human peripheral blood cells, normal bone marrow cells and various types of normal tissues, JL1 could be an excellent candidate for an immunodiagnostic and immunotherapeutic tool for hematopoietic malignancies such as leukemia.

Antibodies, Monoclonal↗
PubMed1998

Inhibitory effect of sesquiterpene lactones from Saussurea lappa on tumor necrosis factor-alpha production in murine macrophage-like cells.

Total methanol extract of Saussurea lappa radix (Compositae) showed potent inhibitory effect on the production of tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, in murine macrophage-like cell (RAW264.7 cells) in our previous screening studies on 120 Korean medicinal plants. The activity-guided purification of the plant resulted in the isolation of three components. The chemical structures of the components isolated were established by spectroscopic analyses as sesquiterpene lactones [cynaropicrin (1), reynosin (2), and santamarine (3)]. These three compounds inhibited TNF-alpha production in a dose-dependent manner. The molar concentrations of cynaropicrin, reynosin, and santamarine producing 50% inhibition (IC50) of TNF-alpha production were 2.86 micrograms/ml (8.24 microM), 21.7 micrograms/ml (87.4 microM), and 26.2 micrograms/ml (105 microM), respectively. However, treatment with sulphydryl (SH) compounds such as L-cysteine, dithiothreitol, and 2-mercaptoethanol abrogated the inhibitory effect of cynaropicrin on TNF-alpha production. Therefore, we conclude that the principal inhibitory component of Saussurea lappa is cynaropicrin and its inhibitory effect is mediated through conjugation with SH-groups of target proteins.

Animals↗
PubMed1998

HLA haplotypes in Koreans based on 107 families.

There are marked differences in the distribution of HLA haplotypes among different populations, and multilocus HLA haplotypes can best be studied by family analysis. In the present study, 107 Korean families were analyzed for HLA-A, B, C, DR, and DQ antigens and haplotypes. Allele frequencies of more than 10% for class I antigens were A2, A24, A33, B44, B62, Cwl, Cw7, Cw9, Cw10, and C blank (CBL) and those for class II antigens were DR4, DR8, DR13, DR15, DQ1, DQ3, DQ4 and DQ7. In the analysis of HLA haplotypes, 18 kinds of A-B-DR and 11 kinds of A-C-B-DR-DQ haplotypes occurred at frequencies of more than 1%, comprising 34% and 24% of the total theoretical haplotypes, respectively. The five most common A-B-DR haplotypes were exclusively related with the five most common A-C-B-DR-DQ haplotypes (frequency>2%). These remarkably conserved five-locus haplotypes in Koreans were A33-CBL-B44-DR13-DQ1 (5.4%), A24-Cw7-B7-DR1-DQ1 (3.5%), A33-Cw7-B44-DR7-DQ2 (3.0%), A33-Cw10-B58-DR13-DQ1 (2.3%), and A30-Cw6-B13-DR7-DQ2 (2.3%). Comparison of the distribution of A-B-DR haplotypes among East Asian populations revealed that Koreans are closest to Japanese, but show a higher degree of polymorphism in the distribution of HLA haplotypes compared to Japanese. The results obtained in this study will be useful as basic data on Koreans for anthropology and organ transplantation.

Alleles↗
PubMed1998

Diversity of HLA-B61 alleles and haplotypes in East Asians and Spanish Gypsies.

The distribution of HLA-B61 alleles and their association with HLA-C and DRB1 alleles were investigated in six East Asian populations (South Korean, Chinese Korean, Man (Manchu), Northern Han, Mongolian and Buryat) and Spanish Gypsies and compared to our previous report on the Japanese population. The alleles were identified using a group-specific polymerase chain reaction (PCR) and genomic DNA followed by hybridization with sequence-specific oligonucleotide probes (SSOP). Both HLA-B*4002 and B*4006 were commonly detected in the South Korean, Chinese Korean, Man, Northern Han and Japanese populations, while HLA-B*4002 was predominant in the Mongolian and Buryat populations. Strong associations of B*4002 with Cw*0304 and of B*4006 with Cw*0801 were commonly observed in these East Asian populations. In contrast, in Spanish Gypsies, only HLA-B*4006 was found and the allele exhibited a strong association with Cw*1502. HLA-B*4003 was also identified in the South Korean, Chinese Korean, Northern Han, Mongolian and Japanese populations at relatively low frequencies, and exhibited an association with Cw*0304. Moreover, the association of these B61 alleles with the DRB1 alleles revealed considerable diversity among the different populations. HLA-B*4004 and B*4009 were not observed in these populations. Consequently, the frequencies of the B61 alleles varied among the different East Asian populations, but the individual B61 alleles were carried by specific haplotypes often regardless of the ethnic differences.

Alleles↗
PubMed1997

Enzyme-substrate intermediate at a specific lysine residue is required for deoxyhypusine synthesis. The role of Lys329 in human deoxyhypusine synthase.

Deoxyhypusine synthase catalyzes the first step in the post-translational synthesis of hypusine [Nepsilon-(4-amino-2-hydroxybutyl)lysine] in eukaryotic translation initiation factor 5A. We recently reported biochemical evidence for a covalent enzyme-substrate intermediate involving a specific lysine residue (Lys329) in human deoxyhypusine synthase (Wolff, E. C., Folk, J. E., and Park, M. H. (1997) J. Biol. Chem. 272, 15865-15871). In an effort to evaluate the role of this enzyme-substrate intermediate in catalysis, we carried out site-directed mutagenesis (Lys to Arg and/or Ala) of the conserved lysine residues in human deoxyhypusine synthase. A drastic reduction in enzyme intermediate formation and enzymatic activities was observed with mutant proteins with substitution at Lys287 but not with those with mutations at residues 141, 156, 205, 212, 226, 251, or 338. Lys to Ala or Lys to Arg substitution at Lys329 totally abolished covalent enzyme-substrate intermediate formation and deoxyhypusine synthesis activity, indicating that Lys329 is the unique site for the enzyme intermediate and that it is absolutely required for deoxyhypusine synthesis in the eukaryotic translation initiation factor 5A precursor. The K329A mutant showed spermidine cleavage activity ( approximately 6% of the wild type enzyme) suggesting that in contrast to deoxyhypusine synthesis, spermidine cleavage can occur without enzyme intermediate formation.

Biopolymers↗
PubMed1997

Enzyme-substrate intermediate formation at lysine 329 of human deoxyhypusine synthase.

Deoxyhypusine (Nepsilon-(4-aminobutyl)lysine) is the key intermediate in the posttranslational synthesis of the unique amino acid, hypusine (Nepsilon-(4-amino-2-hydroxybutyl)lysine). Deoxyhypusine synthase catalyzes the formation of deoxyhypusine by conjugation of the butylamine moiety of spermidine to the epsilon-amino group of one specific lysine residue of the eukaryotic translation initiation factor 5A (eIF-5A) precursor protein. However, in the absence of the eIF-5A precursor, catalysis involves only the NAD-dependent cleavage of spermidine to generate 1,3-diaminopropane and a putative 4-carbon amine intermediate that gives rise to Delta1-pyrroline. We have obtained evidence for a covalent enzyme-substrate intermediate that accumulates in the absence of the eIF-5A precursor. Incubation of human recombinant enzyme with [1, 8-3H]spermidine and NAD, followed by reduction with NaBH3CN, resulted in specific radiolabeling of the enzyme. The radioactive component in the reduced enzyme intermediate was identified as deoxyhypusine and was shown to occur at a single locus. The fact that labeled deoxyhypusine was found after treatment with a reducing agent suggests an intermediate with the butylamine moiety derived from spermidine attached through an imine linkage to the epsilon-amino group of a specific lysine residue of the enzyme. This residue has been identified as lysine 329. Separate experiments showing efficient transfer of labeled butylamine moiety from enzyme intermediate to eIF-5A precursor strongly support a reaction mechanism involving an imine intermediate.

Catalysis↗