• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.363-368
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• 2017

Methylotrophy is able to use reduced one-carbon compound, such as methanol and methylamine, as a sole carbon source. Methylobacterium extorquens AM1 is the most extensively studied methylotroph utilizing serine-isocitrate lyase cycle. Because the Poly 3-hydroxybutyrate (PHB) synthesis pathway in M. extorquens AM1 is likely to interlink with EMCP (ethylmalonyl-CoA pathway), glyoxylate, and TCA cycles, regulation of PHB production is needed to produce EMCP-derived acid or TCA acids. To adjust carbon flux to PHB production, PhaR, which seems to have function of regulator of PHB synthesis and acetyl-CoA flux, was knocked out in M. extorquens AM1 by using markerless gene deletion methods. As a result, PHB granules were remarkably reduced in the knockout strain ${\Delta}phaR$ compared to parental strain. Although lag phase was extended for 12h, ${\Delta}phaR$ showed similar cell growth and methanol consumption rate compared to wild type.

• Journal of Microbiology and Biotechnology
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• v.19 no.1
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• pp.23-36
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• 2009

In the present work, the metabolic network of primary metabolism of the slow-growing myxobacterium Sorangium cellulosum was reconstructed from the annotated genome sequence of the type strain So ce56. During growth on glucose as the carbon source and asparagine as the nitrogen source, So ce56 showed a very low growth rate of $0.23\;d^{-1}$, equivalent to a doubling time of 3 days. Based on a complete stoichiometric and isotopomer model of the central metabolism, $^{13}C$ metabolic flux analysis was carried out for growth with glucose as carbon and asparagine as nitrogen sources. Normalized to the uptake flux for glucose (100%), cells recruited glycolysis (51%) and the pentose phosphate pathway (48%) as major catabolic pathways. The Entner-Doudoroff pathway and glyoxylate shunt were not active. A high flux through the TCA cycle (118%) enabled a strong formation of ATP, but cells revealed a rather low yield for biomass. Inspection of fluxes linked to energy metabolism revealed that S. cellulosum utilized only 10% of the ATP formed for growth, whereas 90% is required for maintenance. This explains the apparent discrepancy between the relatively low biomass yield and the high flux through the energy-delivering TCA cycle. The total flux of NADPH supply (216%) was higher than the demand for anabolism (156%), indicating additional reactions for balancing of NADPH. The cells further exhibited a highly active metabolic cycle, interconverting $C_3$ and $C_4$ metabolites of glycolysis and the TCA cycle. The present work provides the first insight into fluxes of the primary metabolism of myxobacteria, especially for future investigation on the supply of cofactors, building blocks, and energy in myxobacteria, producing natural compounds of biotechnological interest.

• Microbiology and Biotechnology Letters
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• v.38 no.4
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• pp.349-361
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• 2010

In this review, the current knowledge of the carbon metabolism and global carbon regulation in Corynebacterium glutamicum are summarized. C. gluamicum has phosphotransferase system (PTS) for the utilization of sucrose, glucose, and fructose. C. glutamicum does not show any preference for glucose when various sugars or organic acids are present with glucose, and thus cometabolizes glucose with other sugars or organic acids. The molecular mechanism of global carbon regulation such as carbon catabolite repression (CCR) in C. glutamicum is quite different to that in Gram-negative or low-GC Gram-positive bacteria. GlxR (glyoxylate bypass regulator) in C. glutamicum is the cyclic AMP receptor protein (CRP) homologue of E. coli. GlxR has been reported to regulate genes involved in not only glyoxylate bypass, but also central carbon metabolism and CCR including glycolysis, gluconeogenesis, and tricarboxylic acid (TCA) cycle. Therefore, GlxR has been suggested as a global transcriptional regulator for the regulation of diverse physiological processes as well as carbon metabolism. Adenylate cyclase of C. glutamicum is a membrane protein belonging to class III adenylate cyclases, thus it could possibly be a sensor for some external signal, thereby modulating cAMP level in response to environmental stimuli. In addition to GlxR, three additional transcriptional regulators like RamB, RamA, and SugR are also involved in regulating the expression of many genes of carbon metabolism. Finally, recent approaches for constructing new pathways for the utilization of new carbon sources, and strategies for enhancing amino acid production through genetic modification of carbon metabolism or regulatory network are described.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.119.1-119
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• 2003

The glyoxysomal nature of microbodies was determined in Botryosphaeria dothidea hyphae based on morphology and in situ enzyme characteristics by transmission electron microscopy and cytochemistry. Bound by a single membrane, microbodies had a homogeneous matrix and varied in size ranging from 200 to 400 m in diameter. Microbodies had crystalline inclusion(s) which consisted of parallel arrays of fine tubules in their matrices. Microbodies and lipid globules were frequently placed in close association with each other, forming microbody-lipid globule complexes in hyphae. The cytochemical activities of catalase and malate synthase were localized in matrices of microbodies, showing intense electron-density of the organelle. In addition, the immunogold labeling detected the presence of catalase in multivesicular bodies and hyphal cell walls as well as in matrices and crystalline inclusions of microbodies, supporting the enzyme secretion through cell walls. Meanwhile, isocitrate Iyase was localized only in matrices of microbodies. These results suggest that microbodies, particularly complexed with lipid globules, in the fungal hyphae are functionally defined as glyoxysomes, where glyoxysomal enzymes are biochemically active for the glyoxylate cycle to be a metabolic pathway in gluconeogenesis. (Mycology and Fugus Diseases)

• Journal of Life Science
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• v.29 no.4
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• pp.421-427
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• 2019

Mobilization of storage lipids is critical for the germination of oil seeds, as they supply carbon and energy until photosynthesis commences in cotyledons. In this study, we determined the levels of plant carnitine and associated changes in these levels from seed germination to cotyledon senescence. We also examined changes in the content of unsaturated fatty acids throughout seedling development. Carnitine levels peaked on day 3 at 14.5 nM in cotyledons and decreased sharply to 7.2 nM on day 4. On development day 3 carnitine levels were maintained at around 3 nM until day 7. The unsaturated fatty acid content dropped by half at the same time as carnitine peaked (day-3), and storage lipids were almost depleted by day 5. Thereafter, carnitine was hardly detected until the second stage of cotyledon senescence, at which stage the carnitine content was 6.8 nM, similar to that on day 4 at the time of fatty acid depletion in the cotyledons. Unsaturated fatty acids levels remained constant in green cotyledons but slightly increased in the senescing cotyledons. The latter can be explained by intracellular breakdown of membrane lipids. This is the first such discovery in developing cotyledons and may offer clues regarding other roles of the acetyl unit transport system in plants. The expression of BOU was closely associated with carnitine metabolism during seed germination and cotyledon development. The results provide support for the possibility of carbon re-routing during the glyoxylate cycle in the supply of energy for early germination and development.

• Journal of Life Science
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• v.33 no.8
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• pp.651-662
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• 2023

Peroxisomes, known as microbodies, are a class of morphologically similar subcellular organelles commonly found in most eukaryotic cells. They are 0.2~1.8 ㎛ in diameter and are bound by a single membrane. The matrix is usually finely granular, but occasionally crystalline or fibrillary inclusions are observed. They characteristically contain hydrogen peroxide (H₂O₂) generating oxidases and contain the enzyme catalase, thus confining the metabolism of the poisonous H₂O₂ within these organelles. Therefore, the eukaryotic organelles are greatly dynamic both in morphology and metabolism. Plant peroxisomes, in particular, are associated with numerous metabolic processes, including β-oxidation, the glyoxylate cycle and photorespiration. Furthermore, plant peroxisomes are involved in development, along with responses to stresses such as the synthesis of important phytohormones of auxins, salicylic acid and jasmonic acids. In the past few decades substantial progress has been made in the study of peroxisome biogenesis in eukaryotic organisms, mainly in animals and yeasts. Advancement of sophisticated techniques in molecular biology and widening of the range of genomic applications have led to the identification of most peroxisomal genes and proteins (peroxins, PEXs). Furthermore, recent applications of proteome study have produced fundamental information on biogenesis in plant peroxisomes, together with improving our understanding of peroxisomal protein targeting, regulation, and degradation. Nonetheless, despite this progress in peroxisome development, much remains to be explained about how peroxisomes originate from the endoplasmic reticulum (ER), then assemble and divide. Peroxisomes perform dynamic roles in many phases of plant development, and in this review, we focus on the latest progress in furthering our understanding of plant peroxisome functions, biogenesis, and dynamics.