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Park, Sangkyu,Kim, Da-Hye,Lee, Jong-Yeol,Ha, Sun-Hwa,Lim, Sun-Hyung American Chemical Society 2017 Journal of agricultural and food chemistry Vol.65 No.26
<P>We isolated cDNAs encoding flavonol synthase (FLS) from the red onion 'H6' (AcFLS-H6) and the yellow onion 'Hwangryongball' (AcFLS-HRB). We found three amino acid variations between the two sequences. Kinetic analysis with recombinant proteins revealed that AcFLS-HRB exhibited approximately 2-fold higher catalytic efficiencies than AcFLS-H6 for dihydroflavonol substrates and that both proteins preferred dihydroquercetin to dihydrokaempferol. The expression patterns of flavonoid biosynthesis genes corresponded to the accumulation patterns of flavonoid aglycones in both onions. Whereas the other flavonoid biosynthesis genes were weakly expressed in the HRB sheath compared to that of H6, the expression of FLS was similar in both onions. This relatively enhanced FLS expression, along with the higher activity of AcFLS-HRB, could increase the quercetin production in the HRB sheath. The quercetin content was approximately 12-fold higher than the cyanidin content in the H6 sheath, suggesting that FLS has priority in the competition between FLS and dihydroflavonol 4-reductase (DFR) for their substrate dihydroquercetin.</P>
Rice P450 reductases differentially affect P450-mediated metabolism in bacterial expression systems.
Park, Sangkyu,Kim, Young-Soon,Rupasinghe, Sanjeewa G,Schuler, Mary A,Back, Kyoungwhan Springer-Verlag 2013 Bioprocess and biosystems engineering Vol.36 No.3
<P>We describe cloning and characterization of three rice (Oryza sativa) NADPH-cytochrome P450 reductases (OsCPRs; E.C.1.6.2.4) that are potential donors to plant P450s, including tryptamine 5-hydroxylase (T5H) in serotonin synthesis and cinnamate 4-hydroxylase (C4H) in phenylpropanoid synthesis. All three OsCPR transcripts are induced to varying degrees by stresses. Co-expression of full-length OsCPR1, OsCPR2 and OsCPR3 with either T5H or C4H in E. coli indicated that the OsCPR2/T5H and OsCPR2/C4H constructs displayed the highest T5H and C4H catalytic activities. The N-terminal residues of OsCPR2 were required for peak electron transfer activity to P450 even though deletion mutants with short N-terminal deletions were capable of reducing cytochrome c.</P>
Plant Metabolomics for Plant Chemical Responses to Belowground Community Change by Climate Change
Park, Sangkyu,Seo, Young-Su,Hegeman, Adrian D. 한국식물학회 2014 Journal of Plant Biology Vol.57 No.3
General circulation models on global climate change predict increase in surface air temperature and changes in precipitation. Increases in air temperature (thus soil temperature) and altered precipitation are known to affect the species composition and function of soil microbial communities. Plant roots interact with diverse soil organisms such as bacteria, protozoa, fungi, nematodes, annelids and insects. Soil organisms show diverse interactions with plants (eg. competition, mutualism and parasitism) that may alter plant metabolism. Besides plant roots, various soil microbes such as bacteria and fungi can produce volatile organic compounds (VOCs), which can serve as infochemicals among soil organisms and plant roots. While the effects of climate change are likely to alter both soil communities and plant metabolism, it is equally probable that these changes will have cascading consequnces for grazers and subsequent food web components aboveground. Advances in plant metabolomics have made it possibile to track changes in plant metabolomes as they respond to biotic and abiotic environmental changes. Recent developments in analytical instrumentation and bioinformatics software have established metabolomics as an important research tool for studying ecological interactions between plants and other organisms. In this review, we will first summarize recent progress in plant metabolomics methodology and subsequently review recent studies of interactions between plants and soil organisms in relation to climate change issues.
( Sangkyu Park ),( Dongbum Kim ),( Jinsoo Kim ),( Hyung-joo Kwon ),( Younghee Lee ) 생화학분자생물학회 2023 BMB Reports Vol.56 No.12
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to various clinical symptoms including anemia. Lipocalin-2 has various biological functions, including defense against bacterial infections through iron sequestration, and it serves as a biomarker for kidney injury. In a human protein array, we observed increased lipocalin-2 expression due to parental SARS-CoV-2 infection in the Calu-3 human lung cancer cell line. The secretion of lipocalin-2 was also elevated in response to parental SARS-CoV-2 infection, and the SARS-CoV-2 Alpha, Beta, and Delta variants similarly induced this phenomenon. In a Calu-3 implanted mouse xenograft model, parental SARSCoV- 2 and Delta variant induced lipocalin-2 expression and secretion. Additionally, the iron concentration increased in the Calu-3 tumor tissues and decreased in the serum due to infection. In conclusion, SARS-CoV-2 infection induces the production and secretion of lipocalin-2, potentially resulting in a decrease in iron concentration in serum. Because the concentration of iron ions in the blood is associated with anemia, this phenomenon could contribute to developing anemia in COVID-19 patients. [BMB Reports 2023; 56(12): 669-674]
Sangkyu Park,Chan-Byoung Chae,Saewoong Bahk IEEE 2015 IEEE wireless communications Vol.22 No.3
<P>To satisfy the ever increasing capacity demand and quality of service requirements of users, 5G cellular systems will take the form of HetNets that consist of macrocells and small cells. To build and operate such systems, mobile operators have given significant attention to cloud radio access networks, C-RANs, due to their beneficial features of performance optimization and cost effectiveness. Along with the architectural enhancement of C-RAN, largescale antennas (a.k.a. massive MIMO) at cell sites contribute greatly to increased network capacity either with higher spectral efficiency or through permitting many users at once. In this article, we discuss the challenging issues of CRAN- based HetNets (H-CRAN), especially with respect to large-scale antenna operation. We provide an overview of existing C-RAN architectures in terms of large-scale antenna operation and promote a partially centralized approach. This approach remarkably reduces fronthaul overheads in C-RANs with large-scale antennas. We also provide some insights into its potential and applicability in the fronthaul bandwidth-limited H-CRAN with large-scale antennas.</P>
Before/After Precoding Massive MIMO Systems for Cloud Radio Access Networks
Park, Sangkyu,Chae, Chan-Byoung,Bahk, Saewoong The Korea Institute of Information and Commucation 2013 Journal of communications and networks Vol.15 No.4
In this paper, we investigate two types of in-phase and quadrature-phase (IQ) data transfer methods for cloud multiple-input multiple-output (MIMO) network operation. They are termed "after-precoding" and "before-precoding". We formulate a cloud massive MIMO operation problem that aims at selecting the best IQ data transfer method and transmission strategy (beamforming technique, the number of concurrently receiving users, the number of used antennas for transmission) to maximize the ergodic sum-rate under a limited capacity of the digital unit-radio unit link. Based on our proposed solution, the optimal numbers of users and antennas are simultaneously chosen. Numerical results confirm that the sum-rate gain is greater when adaptive "after/before-precoding" method is available than when only conventional "after-precoding" IQ-data transfer is available.
Park, Sangkyu,Cho, Kang-Hyun The Korean Society for Integrative Biology 2003 Korean journal of biological sciences Vol.7 No.4
To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizaniz latifolia. To separate the leaching process from microbial decay, we used $HgCl_2$ to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash-free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=AㆍX/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K > Na > Mg > P > Ca > N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.