Y S Park

Inje University, Kimhae, South Gyeongsang, South Korea

Are you Y S Park?

Claim your profile

Publications (12)44.75 Total impact

  • Article: Phase II study of everolimus with biomarker exploration in patients with advanced gastric cancer refractory to chemotherapy including fluoropyrimidine and platinum.
    [show abstract] [hide abstract]
    ABSTRACT: To evaluate the activity and safety of everolimus and identify potential biomarkers for efficacy of everolimus in patients with advanced gastric cancer (AGC), who failed both fluoropyrimidine and platinum. Fifty-four patients received everolimus (10 mg day(-1)). The primary objective was to determine the 4-month progression-free survival (PFS) rate, assumed to be 30%. We additionally investigated the potential biomarkers for everolimus as an exploratory endpoint in those who underwent tumour biopsies. Two patients (3.7%) achieved partial response and the disease control rate (DCR) was 38.9%. At a median follow-up duration of 8.7 months, the 4-month PFS rate was 18.4%, not fulfilling the primary hypothesis, with a median PFS of 1.7 months and a median overall survival of 8.3 months. The high expression of pS6(Ser240/4) at baseline was significantly associated with higher DCR (P=0.043) and prolonged PFS (P=0.001). Grade 1/2 asthenia (96.3%) recorded as the leading toxicity and hyperglycaemia (20.4%) was the most common non-hematological grade 3/4 toxicity. Three patients experienced grade 3/4 pneumonitis. Notably, two experienced treatment-related deaths. Everolimus is active against a limited number of patients with AGC. pS6(Ser240/4) may be a potential predictive biomarker for everolimus, which requires validation. Careful monitoring is necessary despite generally favourable toxicity profile.
    British Journal of Cancer 02/2012; 106(6):1039-44. · 5.04 Impact Factor
  • Article: Comparison of medial and lateral meniscal transplantation with regard to extrusion of the allograft, and its correlation with clinical outcome.
    [show abstract] [hide abstract]
    ABSTRACT: We compared extrusion of the allograft after medial and lateral meniscal allograft transplantation and examined the correlation between the extent of extrusion and the clinical outcome. A total of 73 lateral and 26 medial meniscus allografts were evaluated by MRI at a mean of 32 months (24 to 59) in 99 patients (67 men, 32 women) with a mean age of 35 years (21 to 52). The absolute values and the proportional widths of extruded menisci as a percentage were measured in coronal images that showed maximum extrusion. Functional assessments were performed using Lysholm scores. The mean extrusion was 4.7 mm (1.8 to 7.7) for lateral menisci and 2.9 mm (1.2 to 6.5) for medial menisci (p < 0.001), and the mean percentage extrusions were 52.0% (23.8% to 81.8%) and 31.2% (11.6% to 63.4%), respectively (p < 0.001). Mean Lysholm scores increased significantly from 49.0 (10 to 83) pre-operatively to 86.6 (33 to 99) at final follow-up for lateral menisci (p = 0.001) and from 50.9 (15 to 88) to 88.3 (32 to 100) for medial menisci (p < 0.001). The final mean Lysholm scores were similar in the two groups (p = 0.312). Furthermore, Lysholm scores were not found to be correlated with degree of extrusion (p = 0.242). Thus, transplanted lateral menisci extrude more significantly than transplanted medial menisci. However, the clinical outcome after meniscal transplantation was not found to be adversely affected by extrusion of the allograft.
    Journal of Bone and Joint Surgery - British Volume 02/2012; 94(2):190-3. · 2.83 Impact Factor
  • Article: Recurrence after successful treatment among patients with multidrug-resistant tuberculosis.
    [show abstract] [hide abstract]
    ABSTRACT: A retrospective review was conducted of patients with multidrug-resistant tuberculosis (MDR-TB) to elucidate the rate of recurrence after successful treatment. Of 123 MDR-TB patients, 90 were declared as 'cured' or 'treatment completed' after individualised treatment; four (4.4%) experienced recurrence. All patients with recur- rent MDR-TB were documented as 'treatment completed' after treatment. Recurrence of MDR-TB is possible after successful treatment, particularly among those documented as 'treatment completed'.
    The international journal of tuberculosis and lung disease: the official journal of the International Union against Tuberculosis and Lung Disease 10/2011; 15(10):1331-3. · 2.73 Impact Factor
  • Article: Molecular cloning and disruption of a novel gene encoding UDP-glucose: tetrahydrobiopterin alpha-glucosyltransferase in the cyanobacterium Synechococcus sp. PCC 7942.
    Y K Choi, Y K Hwang, Y S Park
    [show abstract] [hide abstract]
    ABSTRACT: The gene encoding UDP-glucose:tetrahydrobiopterin alpha-glucosyltransferase (BGluT) was cloned from the genomic DNA of Synechococcus sp. PCC 7942. The encoded protein consisting of 359 amino acid residues was verified in vitro and in vivo to be responsible for the synthesis of tetrahydrobiopterin (BH4)-glucoside produced in the organism. The BGluT gene is the first cloned in pteridine glycosyltransferases and also a novel one cloned so far in UDP-glycosyltransferases. The mutant cells disrupted in the BGluT gene produced only aglycosidic BH4 at a level of 8.3% of the BH4-glucoside in wild type cells and exhibited half of the wild type growth in normal photoautotrophic conditions. These results suggest that the glucosylation of BH4 is required for the maintenance of the high cellular concentration of the compound, thereby supporting the normal growth of Synechococcus sp. PCC 7942.
    FEBS Letters 09/2001; 502(3):73-8. · 3.54 Impact Factor
  • Source
    Article: Purification and characterization of UDP-glucose:tetrahydrobiopterin glucosyltransferase from Synechococcus sp. PCC 7942.
    [show abstract] [hide abstract]
    ABSTRACT: Tetrahydrobiopterin (BH4)-glucoside was identified from Synechococcus sp. PCC 7942 by HPLC analysis and the enzymatic activity of a glycosyltransferase producing the compound from UDP-glucose and BH4. The novel enzyme, named UDP-glucose:BH4 glucosyltransferase, has been purified 846-fold from the cytosolic fraction of Synechococcus sp. PCC 7942 to apparent homogeneity on SDS-PAGE. The native enzyme exists as a monomer having a molecular mass of 39.2 kDa on SDS-PAGE. The enzyme was active over a broad range of pH from 6.5 to 10.5 but most active at pH 10.0. The enzyme required Mn(2+) for maximal activity. Optimum temperature was 42 degrees C. Apparent K(m) values for BH4 and UDP-glucose were determined as 4.3 microM and 188 microM, respectively, and V(max) values were 16.1 and 15.1 pmol min(-1) mg(-1), respectively. The N-terminal amino acid sequence was Thr-Ala-His-Arg-Phe-Lys-Phe-Val-Ser-Thr-Pro-Val-Gly-, sharing high homology with the predicted N-terminal sequence of an unidentified open reading frame slr1166 determined in the genome of Synechocystis sp. PCC 6803, which is known to produce a pteridine glycoside cyanopterin.
    Biochimica et Biophysica Acta 01/2001; 1524(2-3):183-8. · 4.66 Impact Factor
  • Article: Characterization of recombinant Dictyostelium discoideum sepiapterin reductase expressed in E. coli.
    [show abstract] [hide abstract]
    ABSTRACT: A cDNA clone (SSC801) putatively encoding sepiapterin reductase (SR) was obtained from the expressed sequence tag clones of Dictyostelium discoideum. The cDNA sequence of 878 nucleotides constituted an ORF of 265 amino acid residues but was missing a few N-terminal residues. The deduced amino acid sequence showed 29.8% identity with mouse SR sequence and a molecular mass of 29,969 Da. The coding sequence was cloned in E. coli expression vector and overexpressed. The purified His-tag recombinant enzyme was confirmed to have the genuine activity of SR to produce tetrahydrobiopterin from 6-pyruvoyltetrahydropterin in a coupled assay with 6-pyruvoyltetrahydropterin synthase as well as dihydrobiopterin from sepiapterin. However, dictyopterin was not observed in our assay condition. The enzyme was also inhibited by N-acetylserotonin and to a lesser extent by melatonin. Km values for NADPH and sepiapterin were 51.8+/-2.7 microM and 40+/-2 microM, respectively. Vmax was determined as 0.14 micromol/min/mg of protein.
    Molecules and Cells 09/2000; 10(4):405-10. · 2.18 Impact Factor
  • Article: Identification of the genes encoding enzymes involved in the early biosynthetic pathway of pteridines in Synechocystis sp. PCC 6803.
    [show abstract] [hide abstract]
    ABSTRACT: The biosynthetic pathway for the pteridine moiety of cyanopterine, as well as tetrahydrobiopterine, has been investigated in Synechocystis sp. PCC 6803. Open reading frames slr0426, slr1626, slr0078 and sll0330 of the organism putatively encoding GTP cyclohydrolase I, dihydroneopterine aldolase, 6-pyruvoyltetrahydropterine synthase and sepiapterine reductase, respectively, have been cloned into T7-based vectors for expression in Escherichia coli. The recombinant proteins have been purified to homogeneity and demonstrated to possess expected genuine activities except that of sll0330. Our result is the first direct evidence for the functional assignment of the open reading frames in Synechocystis sp. PCC 6803. Furthermore, the 6-pyruvoyltetrahydropterine synthase gene is demonstrated for the first time in prokaryotes. Based on the result, biosynthesis of cyanopterine is discussed.
    FEMS Microbiology Letters 08/1999; 176(1):169-76. · 2.04 Impact Factor
  • Article: Isolation of a psychrotrophic Azospirillum sp. and characterization of its extracellular protease.
    [show abstract] [hide abstract]
    ABSTRACT: A novel psychrotrophic bacterium secreting a protease was isolated from a mountain soil in Korea. On the basis of a 16S rDNA sequence analysis and physiological properties, the isolate was identified as an Azospirillum sp. The protease purified from the culture supernatant was a monomer in its native form with an apparent molecular mass of 48.6 kDa on SDS-PAGE. The protease was active in a broad pH range around 8.5 and at temperatures up to 40 degrees C and stable at temperatures below 30 degrees C for 3 days. The proteolytic activity was inhibited by iodoacetamide and EDTA. The Mg2+ ion did not activate the enzyme much but reversed the inhibition by EDTA, suggesting that the protease belongs to a cysteine protease stabilized by the Mg2+ ion.
    FEMS Microbiology Letters 06/1999; 174(1):173-8. · 2.04 Impact Factor
  • Article: Cloning of mouse sepiapterin reductase gene and characterization of its promoter region.
    [show abstract] [hide abstract]
    ABSTRACT: We have isolated and characterized approximately 5 kb mouse sepiapterin reductase gene (Spr) and a highly homologous pseudogene (Sprp). The authentic Spr gene is present as a single copy in the mouse genome and is composed of three exons containing the entire coding region. The primer extension experiment located the transcription initiation site in a putative pyrimidine-rich Inr element. The promoter region of the Spr gene is embedded within a CpG island. It was shown that the promoter region is devoid of distinctive TATA and CAAT boxes. Transient transfection of a series of 5' deletion derivatives of the Spr promoter showed the sequence between -83 and -51 to be essential for promoter activity. The pseudogene Sprp lacks promoter region and exon 3.
    Biochimica et Biophysica Acta 05/1999; 1445(1):165-71. · 4.66 Impact Factor
  • Article: Characterization of a novel unconjugated pteridine glycoside, cyanopterin, in Synechocystis sp. PCC 6803.
    [show abstract] [hide abstract]
    ABSTRACT: A new pteridine glycoside, called cyanopterin, was isolated from Synechocystis sp. PCC 6803 and its structure was elucidated as 6-[1-(4-O-methyl-(alpha-d-glucuronyl)-(1, 6)-(beta-d-galactosyloxy]methylpterin by chemical degradation and 1H- and 13C-NMR spectroscopic means. Cyanopterin is constitutively synthesized at a relatively high intracellular concentration that is comparable to that of chlorophyll a in a molar ratio of approximately 1 to 1.6. The in vivo oxidation state of cyanopterin is primarily the fully reduced 5,6,7,8-tetrahydro form. The cellular function is unknown at present. The findings have established a model system, using Synechocystis sp. PCC 6803, for studies of the physiological functions of unconjugated pteridine glycosides found mostly in cyanobacteria.
    Biochimica et Biophysica Acta 02/1999; 1410(1):61-70. · 4.66 Impact Factor
  • Article: Isolation and characterization of the Drosophila melanogaster cDNA encoding the sepiapterin reductase.
    [show abstract] [hide abstract]
    ABSTRACT: We have isolated and characterized the cDNA encoding Drosophila melanogaster sepiapterin reductase (SR). The amino acid sequence deduced from the cDNA sequence was 29% identical to those of mammalian SRs. The active site residues proposed from the three-dimensional structure of mouse SR are well conserved in Drosophila SR. The protein-coding region of the cDNA was expressed in Escherichia coli as a histidine fusion protein, and the resulting recombinant protein proved to have SR activity. The SR activity of the recombinant protein was inhibited by two indoleamines, N-acetyl serotonin and melatonin. Southern analysis suggests that the Drosophila SR gene is encoded by a single copy gene. RNA blot analysis revealed that the gene expresses 1.5 kb mRNA in both adult heads and bodies.
    Biochimica et Biophysica Acta 12/1998; 1443(1-2):239-44. · 4.66 Impact Factor
  • Article: Identification of three novel mutations in Korean phenylketonuria patients: R53H, N207D, and Y325X.
    Human Mutation 02/1998; Suppl 1:S121-2. · 5.69 Impact Factor