Oksoo Han

• PhD
• Professor (Full) at Chonnam National University

Rice prolamins are categorized into three groups by molecular size (10, 13, or 16 kDa), while the 13 kDa prolamins are assigned to four subgroups (Pro13a-I, Pro13a-II, Pro13b-I, and Pro13b-II) based on cysteine residue content. Since lowering prolamin content in rice is essential to minimize indigestion and allergy risks, we generated four knockout...

Rice prolamins are categorized into three groups by molecular size (10, 13, or 16 kDa), while the 13 kDa prolamins are assigned to four subgroups (Pro13a-I, Pro13a-II, Pro13b-I, and Pro13b-II) based on cysteine residue content. Here, we generated four knockout strains of rice using CRISPR-Cas9, each of which demonstrated selectively reduced express...

The glutelins are a family of abundant plant proteins comprised of four glutelin subfamilies (GluA, GluB, GluC, and GluD) encoded by 15 genes. In this study, expression of subsets of rice glutelins were suppressed using CRISPR-Cas9 gene-editing technology to generate three transgenic rice variant lines, GluA1, GluB2, and GluC1. Suppression of the t...

The peroxygenase pathway plays pivotal roles in plant responses to oxidative stress and other environmental stressors. Analysis of a network of co-expressed stress-regulated rice genes demonstrated that expression of OsPXG9 is negatively correlated with expression of genes involved in jasmonic acid biosynthesis. DNA sequence analysis and structure/...

Soybean lipoxygenase was immobilized on nanoporous rice husk silica particles by adsorption, and enzymatic parameters of the immobilized protein, including the efficiency of substrate binding and catalysis, kinetic and operational stability, and the kinetics of thermal inactivation, were investigated. The maximal adsorption efficiency of soybean li...

Genes encoding wheat low-molecular-weight glutenin subunits (LMW-GSs) that confer dough strength and extensibility were previously identified from Korean wheat cultivars. To improve low viscoelasticity of rice (Oryza sativa L.) dough caused by the lack of seed storage proteins comparable to wheat gluten, two genes, LMW03 and LMW28, encoding LMW-GSs...

Allene oxide cyclase (AOC) is a key enzyme in the jasmonic acid (JA) biosynthetic pathway in plants, during which it catalyzes stereospecific conversion of 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid (12,13-EOT) to cis(+)-12-oxophytodienoic acid. Here, rice allene oxide cyclase (OsAOC) was localized to the chloroplast and its native oligomer...

Soybean lipoxygenase, recombinant rice allene oxide synthase-1 and rice allene oxide cyclase were covalently immobilized on nanoporous rice husk silica using two types of linkers: glutardialdehyde and polyethylene glycol. The immobilization efficiency achieved using glutardialdehyde-linked rice husk silica was higher than that achieved using polyet...

Kinetic studies have indicated that imidazole is a competitive inhibitor of rice allene oxide synthase-1 with K i of 34.9, 14.3, 40.3, and 23.3 mM for 13(S)-HPODE, 13(S)-HPOTE, 9(S)-HPODE, and 9(S)-HPOTE as substrates, respectively. Imidazole-free rice allene oxide synthase-1 has a Soret absorbance maximum at 393 nm and occupied high-spin (g = 6.0)...

Allene oxide synthase-1 from Oryza sativa (OsAOS1) localizes to the chloroplast, but lacks a putative chloroplast targeting sequence typically found in dicot AOS. Here, kinetic parameters and the oligomerization state/subunit composition of OsAOS1 were characterized in vitro in the absence or presence of detergent micelles. The catalytic efficiency...

Functional characterization of a defensin, J1-1, was conducted to evaluate its biotechnological potentiality in transgenic pepper plants against the causal agent of anthracnose disease, Colletotrichum gloeosporioides. To determine antifungal activity, J1-1 recombinant protein was generated and tested for the activity against C. gloeosporioides, res...

Jasmonic acid (JA) and salicylic acid (SA) are critical signaling components involved in various aspects of plant growth, development, and defense. Their constitutive levels vary from plant to plant and also from tissue to tissue within the same plant. Moreover, their quantitative levels change when plant is exposed to biotic and abiotic stresses....

Phylogenetic and amino acid sequence analysis indicated that rice allene oxide synthase-1 (OsAOS1) is CYP74, and is clearly distinct from CYP74B, C and D subfamilies. Regio- and stereo-chemical analysis revealed the dual substrate specificity of OsAOS1 for (cis,trans)-configurational isomers of 13(S)- and 9(S)-hydroperoxyoctadecadienoic acid. GC-MS...

Effects of transgenic expression of dual positional maize lipoxygenase-1 on the defense system were analyzed in rice. The activities of hydroperoxidelyase and antioxidative enzymes (superoxide dismutase, catalase, peroxidase) were increased and high levels of aldehydes including malondialdehyde were produced. The constitutive level of jasmonic was...

Castration of Korean cattle improves quality grade, and it reduces production of testosterone. Carcass traits, steroid hormone concentrations, aromatase activities, and expression levels of androgen receptor (AR) and estrogen receptor α (ERα) genes were compared in longissimus dorsi (LD) muscle and subcutaneous fat tissues between bulls and steers,...

The 12-oxo-phytodienoic acid reductase (OPR) is a key enzyme in jasmonic acid (JA) biosynthesis. Previously, we reported the presence of 13 OPR isogenes (OsOPR1-13) in rice. OsOPRs phylogenetically belong to two subgroups, OPRI and OPRII. OsOPR13 is assigned to the second subgroup, which is involved in JA biosynthesis, while the others are found in...

The maize lipoxgyenase-1 is a non-traditional dual positional specific enzyme and the reaction proceeds via enzyme-initiated catalysis. Bioinformatic analysis indicated that the maize lipoxygenase-1 is structurally more similar to soybean LOX1 than pea LOXN2 in that it has an additional external loop (residues 318-351) in the carboxy-terminal catal...

Unlabelled: Two global approaches were applied to develop an inventory of differentially expressed proteins and genes in rice (cv. Nipponbare) seedling grown on Murashige and Skoog medium with and without jasmonic acid (JA). JA significantly reduced the growth of shoot, root, leaf, and leaf sheath depending on JA concentration (1, 2, 5, 10, 25, an...

Dual positional specific maize lipoxygenase-1 catalyzed the formation of racemic mixtures of four possible regioisomers and was strongly inhibited by the radical scavenger, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinoxy radical. Molecular modeling studies indicated that the oxygen-binding cavity is segregated from the substrate-binding cavity. The da...

Although glycine-rich RNA-binding protein 2 (GRP2) has been implicated in plant responses to environmental stresses, the function and importance of GRP2 in stress responses are largely unknown. Here, we examined the functional roles of GRP2 in Arabidopsis thaliana under high-salinity, cold or osmotic stress. GRP2 affects seed germination of Arabido...

The wound-inducible lipoxygenase obtained from maize is one of the nontraditional lipoxygenases that possess dual positional specificity. In this paper, we provide our results on the determination and comparison of the kinetic constants of the maize lipoxygenase, with or without detergents in the steady state, and characterization of the dependence...

La preparación de muestras en proteómica vegetal es tediosa y requiere modificaciones según el tipo de tejido involucrado. Aquí, describimos un protocolo de extracción de proteínas para especies monocotiledóneas (monocotiledóneas) y dicotiledóneas (dicotiledóneas), que mejora significativamente la solubilización de las proteínas totales

Sample preparation in plant proteomics is tedious, requiring modifications depending on the type of tissue involved. Here, we describe a protein extraction protocol for both monocotyledonous (monocot) and dicotyledonous (dicot) species, which significantly improves the solubilization of total proteins. For example, we used the primary leaf tissue a...

Rice, a first cereal crop whose draft genome sequence from two subspecies (japonica-type cv. Nipponbare and indica-type 93-11) was available in 2002, along with its almost complete genome sequence in 2005, has drawn the attention of researchers worldwide because of its immense impact on human existence. One of the most critical research areas in ri...

Previous studies show that low temperature strongly induces suberin layers in the roots of chilling-sensitive cucumber plants, while in contrast, low temperature produces a much weaker induction of suberin layers in the roots of the chilling-tolerant figleaf gourd [S.H. Lee, G.C. Chung, S. Steudle, Gating of aquaporins by low temperature in roots o...

Fatty acid -3 desaturase (FAD) is the key enzyme catalyzing the formation of trienoic fatty acids. We utilized an Arabidopsis FAD7 gene and the seven independent transgenic rice plants harbouring 1 to 3 copies of this gene were generated. The expression of FAD7 mRNA was different among independent transgenic lines regardless of the copy number. The...

This study presents a kinetic analysis of the response to wounding in rice plants. In particular, jasmonic acid, salicylic acid, and lipoxygenase activity were measured in leaves of wounded rice plants during the early tillering phase. The results show that endogenous jasmonic acid transiently increases to a maximum 30 min after wounding (jasmonic...

Plant jasmonic acid (JA) and structurally similar animal prostaglandins play pivotal roles in regulating cellular responses against environmental cues, including the innate immune response(s). In plants, JA and its immediate precursor 12-oxo-phytodienoic acid (OPDA) are synthesized by the octadecanoid pathway, which employs at least five enzymes (l...

To understand the molecular mechanism of mammary gland involution we identified involution-induced clones by differential screening of a mouse mammary gland cDNA library. Characterization of clones by sequencing and Northern analysis showed that expression of 24p3 was induced during involution of the mammary gland. RNA in situ hybridization showed...

Mitogen-activated protein kinase 1 (MK1) from Capsicum annuum was previously cloned and characterized. MK1 is highly conserved in plants and its amino acid sequence is 92% identical to wound-inducible protein kinase (WIPK) from tobacco. In C. annuum, MK1 is transcriptionally activated by wounding. In the present work, the MK1 gene was introduced in...

In an effort to asses the effect of Val311Met point mutation of Bacillus subtilis protoporphyrinogen oxidase on the resistance to diphenyl ether herbicides, a Val311Met point mutant of B. subtilis protoporphyrinogen oxidase was prepared, heterologously expressed in Escherichia coli, and the purified recombinant Val311Met mutant protoporphyrinogen o...

Rice (Oryza sativa L.) is a tropical crop, but is also grown in temperate regions in late spring to summer. Cold temperature damage is a common problem for early-planted rice in temperate countries. Physiological responses to chilling, including antioxidative enzyme activity, were investigated in rice to identify mechanisms of chilling tolerance. P...

Previously, we reported rice (Oryza sativa L. japonica type cv. Nipponbare) allene oxide synthase (OsAOS) and cyclase (OsAOC) genes of the octadecanoid pathway. Here we have isolated a 12-oxo-phytodienoic acid reductase gene, called OsOPR1, encoding the last committed enzymatic step on the octadecanoid pathway leading to jasmonic acid (JA) biosynth...

Lipoxygenases (LOXs) catalyze the formation of fatty acid hydroperoxides involved in responses to stresses. This study examines the expression of a non-traditional dual positional specific maize LOX in response to wounding or methyl jasmonate (MeJA). Full-length maize LOX cDNA was expressed in Escherichia coli, and recombinant LOX was purified and...

Superoxide dismutase, peroxidase and catalase are major antioxidative enzymes that contribute to the oxidative stress response in plants. The activity of these enzymes was measured in wound-stressed rice plants that were wounded at seedling stage, maximum tillering stage or flowering stage. Kinetics of enzyme activity were examined in leaf extracts...

The gene encoding rice allene oxide synthase, OsAOS, was intronless and had nucleotide sequences with the high GC content of 67%. Deduced amino acid sequences had very high similarity with other AOS proteins, in particular 74% similarity to barley, characterized by the conserved motifs of P450 cytochrome of the CYP74A family. Purified recombinant r...

Wound-responsive lipoxygenase full-length cDNA from Zea mays was used to heterologously express the lipoxygenase enzyme and positional specificity of the lipoxygenase reaction was determined. The purified lipoxygenase catalyzed the conversion of α-linolenic acid into both 13-hydroperoxylinolenic acid and 9-hydroperoxylinolenic acid with a ratio of...

A wound-inducible Arabidopsis plastid omega-3 fatty acid desaturase (fad7) cDNA was obtained. Transgenic tobacco plants were produced by integration of the antisense fad7 DNA fragments under the control of a CaMV 35S promoter into the genome. Two transgenic T1 lines, AsFAD714 and 716, showed a strong expression of the antisensefad7 and reduced amou...

To understand molecular mechanisms of mouse mammary gland involution, clones were isolated by differential screening of a cDNA library. Partial sequences of a clone showed 100% identity to cDNA sequences of mouse lysozyme P gene. Northern analysis was performed to examine expression levels of lysozyme mRNA in mammary gland at several physiological...

Two MAP kinases, MK1 and MK2, were cloned from Capsicum annuum (pepper) cv. Subicho using a parsley MAP kinase gene as a heterologous probe. MK1 and MK2 encode stress-inducible protein kinases that can contribute to the response to wounding, UV-C, and cold. MK1 has a 92% amino acid identity with WIPK of tobacco. It was transcriptionally induced in...

Previous studies indicate that B. subtilis protoporphyrinogen oxidase is poorly inhibited by diphenyl ether herbicides. To better understand the basis of this insensitivity, the enzyme was overexpressed as a soluble protein in E. coli, purified and characterized. The mechanism of oxidation of B. subtilis protoporphyrinogen IX was studied and the en...

A strongly conserved threonine residue in the I-helix of cytochrome P450 enzymes participates in a proton delivery system for binding and cleavage of dioxygen molecules. 6-Deoxyerythronol ide B hydroxylase (P450eryF) is unusual in that the conserved threonine residue is replaced by alanine in this enzyme. On the basis of crystal structures of subst...

Protoporphyrinogen oxidase (Protox), the penultimate step enzyme of the branch point for the biosynthetic pathway of Chi and hemes, is the target site of action of diphenyl ether (DPE) herbicides. However, Bacillus subtilis Protox is known to be resistant to the herbicides. In order to develop the herbicide-resistant plants, the transgenic rice pla...

ジフェニルエーテル系 (DPEs) 除草剤に対する植物の反応を評価する時に用いる手法の葉切片法は, 植物をある葉期まで生育させることや植物を切って行うことなどの短所がある. そこで, DPEs系除草剤, オキシフルオルフェンの遺伝子組み換えイネの抵抗性程度を評価する手法の確立を目的として発芽率及び枯死率の測定を行った. この評価法はオキシフルオルフェンに対する抵抗性程度がより早い時期の出芽時に, かつ植物を傷つけずに判断できる利点を持つ. 更に, この手法はオキシフルオルフェンの作用を評価する際のパラメーターである脂質過酸化作用の反応と高い相関性が認められ簡易・迅速な評価法として有効であると判断された.

In an effort to understand the function of the eryBVII gene in the erythromycin biosynthetic gene cluster, we overexpressed the eryBVII gene in E. coli and TDP-6-deoxy-L-threo-D-glycero-4-hexulose was used as a substrate of the overexpressed EryBVII enzyme. The enzymatic reaction product was chemically modified by reduction and peracetylation. Stru...

Tn an effort to develop transgenic plants resistant to diphenyl ether herbicides, vee introduced the protoporphyrinogen oxidase (EC 1.3.3.4) gene of Bacillus subtilis into tobacco plants, The results from a Northern analysis and leaf disc assay indicate that the expression of the B. subtilis protoporphyrinogen oxidase gene under the cauliflower mos...

Aziridine-2-carboxylates were prepared from the reaction of hexahydro-1,3,5-triazines or N-methoxymethylanilines with alkyl diazoacetates in the presence of Lewis acid catalyst in high yield.

A highly conserved threonine in the active site of cytochromes P450 has been proposed to participate in O2 binding and cleavage. Cytochrome P450eryF is unusual in having alanine in place of this threonine and an ordered active site water molecule (Wat 519) which is hydrogen bonded to the substrate 5-hydroxyl group and is in position to operate as a...

Although PLP normally acts to stabilize carbanions in enzymatic reactions, the metallic cofactors of β-lysine mutase and lysine 2,3-aminomutase suggest that substrate and product radicals may be intermediates. PLP could facilitate the β-lysine mutase and lysine 2,3-aminomutase-catalyzed isomerizations by forming aldimines with the substrate amino g...

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Preparations of ascarylose (3,6-dideoxy-L-arabino-hexose), abequose (3,6-dideoxy-D-xylo-hexose), and paratose (3,6-dideoxy-D-ribo-hexose) with stereospecific deuterium labeling at C-3 are discussed. The methods used to synthesize these sugars, such as the hydrogenation of olefins, the displacement of halides, the reduction of epoxides, and the subs...

CDP-6-deoxy-delta 3,4-glucoseen reductase, the key enzyme catalyzing the biosynthetic formation of CDP-ascarylose (CDP-3,6-dideoxy-L-arabino-hexose), was purified from Yersinia pseudotuberculosis by monitoring its NADH:dichlorophenolindolphenol oxidoreductase activity. A protocol consisting of DEAE-cellulose, phenyl-Sepharose, and Sephadex G-100 co...

Reduction of tosylhydrazone derivatives of ketones and aldehydes with sodium cyanoborohydride in acid medium is a mild, albeit versatile, deoxygenation reaction. The reaction mechanism has been proposed to proceed via either a direct hydride attack route or a tautomerization-then-reduction route. By using a mild reduction procedure (NaBHâCN, THF-Me...

The general problem of the synthesis of 3,6-dideoxy sugars containing stereospecifically labeled hydrogen isotope at C-3 is addressed for the specific case of ascarylose (3,6-dideoxy-L-arabino-hexose).

The Zn(II)-catalyzed hydrolysis of 6-carboxy-O-(acetyloxy)-2-pyridinecarboxaldoxime (3) consists of two reaction paths. Rates of the paths were proportional to [Zn(II)][OH -] or to [Zn(II)][OH -] 2. On the other hand, catalysis by the Cu(II) ion was not observed in the hydrolysis of 3. The results were compared with those previously obtained for th...

Script used in title instead of Greek symbols. Thesis (Ph.D.)--University of Minnesota, 1989. Bibliography: leaves 117-122.