• 펄프종이기술
• /
• 제44권4호
• /
• pp.25-31
• /
• 2012

Ionic trash in furnish decreases retention and drainage performance of the microparticle retention system using recycled fibers in closed papermaking system. Two retention systems, such as the microparticle system and the PEO/cofactor system, were compared and analyzed to improve retention. The PEO/cofactor system achieved similar retention performance at low addition level as the microparticle system. Optimum ratio of PEO/cofactor dual polymer system was 1:10. Ash retention was increased when using the fixing agent. As the TMP ratio increased, the PEO/cofactor system was more efficient in retention and drainage than the other system. The high molecular weight and non-ionic polymer retention system had less effect on flocculation hindrance than the traditional electrostatic retention system.

• Journal of Microbiology and Biotechnology
• /
• 제23권12호
• /
• pp.1699-1707
• /
• 2013

During the fermentative production of 1,3-propanediol under high substrate concentrations, accumulation of intracellular 3-hydroxypropionaldehyde will cause premature cessation of cell growth and glycerol consumption. Discovery of oxidoreductases that can convert 3-hydroxypropionaldehyde to 1,3-propanediol using NADPH as cofactor could serve as a solution to this problem. In this paper, the yqhD gene from Klebsiella pneumoniae DSM2026, which was found encoding an aldehyde reductase (KpAR), was cloned and characterized. KpAR showed broad substrate specificity under physiological direction, whereas no catalytic activity was detected in the oxidation direction, and both NADPH and NADH can be utilized as cofactors. The cofactor binding mechanism was then investigated employing homology modeling and molecular dynamics simulations. Hydrogen-bond analysis showed that the hydrogen-bond interactions between KpAR and NADPH are much stronger than that for NADH. Free-energy decomposition dedicated that residues Gly37 to Val41 contribute most to the cofactor preference through polar interactions. In conclusion, this work provides a novel aldehyde reductase that has potential applications in the development of novel genetically engineered strains in the 1,3-propanediol industry, and gives a better understanding of the mechanisms involved in cofactor binding.

• Journal of Microbiology and Biotechnology
• /
• 제28권8호
• /
• pp.1346-1351
• /
• 2018

Oxidoreductases are effective biocatalysts, but their practical use is limited by the need for large quantities of NAD(P)H. In this study, a whole-cell biocatalyst for NAD(P)H cofactor regeneration was developed using the economical substrate glycerol. This cofactor regeneration system employs permeabilized Escherichia coli cells in which the glpD and gldA genes were deleted and the gpsA gene, which encodes $NAD(P)^+-dependent$ glycerol-3-phosphate dehydrogenase, was overexpressed. These manipulations were applied to block a side reaction (i.e., the conversion of glycerol to dihydroxyacetone) and to switch the glpD-encoding enzyme reaction to a gpsA-encoding enzyme reaction that generates both NADH and NADPH. We demonstrated the performance of the cofactor regeneration system using a lactate dehydrogenase reaction as a coupling reaction model. The developed biocatalyst involves an economical substrate, bifunctional regeneration of NAD(P)H, and simple reaction conditions as well as a stable environment for enzymes, and is thus applicable to a variety of oxidoreductase reactions requiring NAD(P)H regeneration.

• BMB Reports
• /
• 제55권9호
• /
• pp.439-446
• /
• 2022

Pyridoxal 5'-phosphate (PLP)-dependent enzymes are ubiquitous, catalyzing various biochemical reactions of approximately 4% of all classified enzymatic activities. They transform amines and amino acids into important metabolites or signaling molecules and are important drug targets in many diseases. In the crystal structures of PLP-dependent enzymes, organic cofactor PLP showed diverse conformations depending on the catalytic step. The conformational change of PLP is essential in the catalytic mechanism. In the study, we review the sophisticated catalytic mechanism of PLP, especially in transaldimination reactions. Most drugs targeting PLP-dependent enzymes make a covalent bond to PLP with the transaldimination reaction. A detailed understanding of organic cofactor PLP will help develop a new drug against PLP-dependent enzymes.

• 한국생명과학회:학술대회논문집
• /
• 한국생명과학회 2007년도 제48회 학술심포지움 및 추계국제학술대회
• /
• pp.107.1-107.1
• /
• 2007

See Full Text

• Applied Biological Chemistry
• /
• 제48권3호
• /
• pp.189-200
• /
• 2005

생물학적 질소고정과정의 연구는 학문적으로나 산업적으로 매우 중요한 과정이다. 본 총설에서는 공업적 질소고정과 비교되는 생물학적 질소고정의 특징을 간단히 살펴보고, Azotobacter vinelandii에서 연구되고 있는 생물학적 질소고정효소의 특징을 다룬다. 생물학적 질소고정과정은 다양한 생명체에서 일어나며, 최근에는 미생물인 A. vinelandii에 그 작용 메커니즘에 관한 연구가 집중되어 있다. 공기중의 질소를 암모니아로 변환시키는 질소고정은 화학적으로 환원 반응에 해당하므로 전자의 공급이 필요하다. 생물학적 질소고정을 담당하는 질소고정효소는 촉매반응을 위해 생물학적인 환원력을 사용하여 전자를 공급받아, Fe 단백질의 $Fe_4S_4$ cluster와 MoFe 단백질의 P-cluster를 거쳐 질소 환원 반응이 일어나는 FeMo-cofactor로 전달한다. 이러한 전자전달의 과정과 수소이온의 전달 과정은 질소고정효소의 반응 메커니즘 이해에 매우 중요한 과정이며, FeMo-cofactor와 질소분자의 상호작용은 생물학적 질소고정 메커니즘의 중심에 있다. 질소고정 작용 메커니즘의 연구에는 X-선 단백질 결정학, EPR과 $M{\ddot{u}}ssbauer$ 등의 다양한 분광학적 방법과, 효소의 기질과 저해제의 상호작용을 연구하고 mutant와 비교하는 생화학적 접근방법, 그리고 FeMo-cofactor의 모델 화합물을 합성하여 연구하는 화학적 방법 등이 적용되었다. 이들 분야의 최근 연구결과를 소개하며, 마지막으로, 다양한 연구 결과에 바탕하여 새로운 질소고정효소의 작용 기작이 제안하였다.

• Bulletin of the Korean Chemical Society
• /
• 제33권2호
• /
• pp.583-588
• /
• 2012

Functional interaction between Drosophila orphan receptor FTZ-F1 (NR5A3) and a segmentation gene product fushi tarazu (FTZ) is crucial for regulating genes related to define the identities of alternate segmental regions in the Drosophila embryo. FTZ binding to the ligand-binding domain (LBD) of FTZ-F1 is of essence in activating its transcription process. We determined solution structures of the cofactor peptide ($FTZ^{PEP}$) derived from FTZ by NMR spectroscopy. The cofactor peptide showed a nascent helical conformation in aqueous solution, however, the helicity was increased in the presence of TFE. Furthermore, $FTZ^{PEP}$ formed ${\alpha}$-helical conformation upon FTZ-F1 binding, which provides a receptor bound structure of $FTZ^{PEP}$. The solution structure of $FTZ^{PEP}$ in the presence of FTZ-F1 displays a long stretch of the ${\alpha}$-helix with a bend in the middle of helix.

• Journal of Microbiology and Biotechnology
• /
• 제26권2호
• /
• pp.226-232
• /
• 2016

Dihydrodipicolinate reductase is an enzyme that converts dihydrodipicolinate to tetrahydrodipicolinate using an NAD(P)H cofactor in L-lysine biosynthesis. To increase the understanding of the molecular mechanisms of lysine biosynthesis, we determined the crystal structure of dihydrodipicolinate reductase from Corynebacterium glutamicum (CgDapB). CgDapB functions as a tetramer, and each protomer is composed of two domains, an Nterminal domain and a C-terminal domain. The N-terminal domain mainly contributes to nucleotide binding, whereas the C-terminal domain is involved in substrate binding. We elucidated the mode of cofactor binding to CgDapB by determining the crystal structure of the enzyme in complex with NADP⁺ and found that CgDapB utilizes both NADH and NADPH as cofactors. Moreover, we determined the substrate binding mode of the enzyme based on the coordination mode of two sulfate ions in our structure. Compared with Mycobacterium tuberculosis DapB in complex with its cofactor and inhibitor, we propose that the domain movement for active site constitution occurs when both cofactor and substrate bind to the enzyme.

• Journal of Microbiology and Biotechnology
• /
• 제13권4호
• /
• pp.501-508
• /
• 2003

Artificial coupling of one enzyme with another can provide an efficient means for the production of industrially important chemicals. Xylose reductase has been recently discovered to be useful in the reductive production of xylitol. However, a limitation of its in vitro or in vivo use is the regeneration of the cofactor NAD(P)H in the enzyme activity. In the present study, an efficient process for the production of xylitol from D-xylose was established by coupling two enzymes. A NADH-dependent xylose reductase (XR) from Pichia stipitis catalyzed the reduction of xylose with a stoichiometric consumption of NADH, and the resulting cofactor $NAD^+$ was continuously re-reduced by formate dehydrogenase (FDH) for regeneration. Using simple kinetic analyses as tools for process optimization, suitable conditions for the performance and yield of the coupled reaction were established. The optimal reaction temperature and pH were determined to be about $30^{\circ}C$ and 7.0, respectively. Formate, as a substrate of FDH, affected the yield and cofactor regeneration, and was, therefore, adjusted to a concentration of 20 mM. When the total activity of FDH was about 1.8-fold higher than that of XR, the performance was better than that by any other activity ratios. As expected, there were no distinct differences in the conversion yields of reactions, when supplied with the oxidized form $NAD^+$ instead of the reduced form NADH, as a starting cofactor for regeneration. Under these conditions, a complete conversion (>99%) could be readily obtained from a small-scale batch reaction.

• Journal of Microbiology and Biotechnology
• /
• 제24권7호
• /
• pp.954-958
• /
• 2014

Succinic semialdehyde dehydrogenase (SSADH) catalyzes the oxidation of succinic semialdehyde (SSA) into succinic acid in the final step of ${\gamma}$-aminobutyric acid degradation. Here, we characterized Bacillus subtilis SSADH (BsSSADH) regarding its cofactor discrimination and substrate inhibition. BsSSADH showed similar values of the catalytic efficiency ($k_{ca}t/K_m$) in both $NAD^+$ and $NADP^+$ as cofactors, and exhibited complete uncompetitive substrate inhibition at higher SSA concentrations. Further analyses of the sequence alignment and homology modeling indicated that the residues of catalytic and cofactor-binding sites in other SSADHs were highly conserved in BsSSADH.