An additional glucose dehydrogenase from Sulfolobus solfataricus: fine-tuning of sugar degradation?

2011 ◽  
Vol 39 (1) ◽  
pp. 77-81 ◽  
Author(s):  
Patrick Haferkamp ◽  
Simone Kutschki ◽  
Jenny Treichel ◽  
Hatim Hemeda ◽  
Karsten Sewczyk ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Dominant Role ◽  
Glucose Dehydrogenase ◽  
Sulfolobus Solfataricus ◽  
Catalytic Efficiency ◽  
Amino Acid Identity ◽  
Fine Tuning ◽  
Effect Of Temperature ◽  
Major Player ◽  
Sugar Degradation

Within the SulfoSYS (Sulfolobus Systems Biology) project, the effect of temperature on a metabolic network is investigated at the systems level. Sulfolobus solfataricus utilizes an unusual branched ED (Entner–Doudoroff) pathway for sugar degradation that is promiscuous for glucose and galactose. In the course of metabolic pathway reconstruction, a glucose dehydrogenase isoenzyme (GDH-2, SSO3204) was identified. GDH-2 exhibits high similarity to the previously characterized GDH-1 (SSO3003, 61% amino acid identity), but possesses different enzymatic properties, particularly regarding substrate specificity and catalytic efficiency. In contrast with GDH-1, which exhibits broad substrate specificity for C5 and C6 sugars, GDH-2 is absolutely specific for glucose. The comparison of kinetic parameters suggests that GDH-2 might represent the major player in glucose catabolism via the branched ED pathway, whereas GDH-1 might have a dominant role in galactose degradation via the same pathway as well as in different sugar-degradation pathways.

scholarly journals MiR-7 in Cancer Development

Biomedicines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 325
Author(s):  
Petra Korać ◽  
Mariastefania Antica ◽  
Maja Matulić
Keyword(s):  
Cell Fate ◽  
Dominant Role ◽  
Tumor Development ◽  
Mrna Translation ◽  
Cell Types ◽  
Fine Tuning ◽  
Non Coding Rna ◽  
Tumor Types ◽  
Different Cell Types ◽  
The Brain

MicroRNAs (miRNAs) are short non-coding RNA involved in the regulation of specific mRNA translation. They participate in cellular signaling circuits and can act as oncogenes in tumor development, so-called oncomirs, as well as tumor suppressors. miR-7 is an ancient miRNA involved in the fine-tuning of several signaling pathways, acting mainly as tumor suppressor. Through downregulation of PI3K and MAPK pathways, its dominant role is the suppression of proliferation and survival, stimulation of apoptosis and inhibition of migration. Besides these functions, it has numerous additional roles in the differentiation process of different cell types, protection from stress and chromatin remodulation. One of the most investigated tissues is the brain, where its downregulation is linked with glioblastoma cell proliferation. Its deregulation is found also in other tumor types, such as in liver, lung and pancreas. In some types of lung and oral carcinoma, it can act as oncomir. miR-7 roles in cell fate determination and maintenance of cell homeostasis are still to be discovered, as well as the possibilities of its use as a specific biotherapeutic.

scholarly journals A Redox-Neutral, Two-Enzyme Cascade for the Production of Malate and Gluconate from Pyruvate and Glucose

2021 ◽  
Vol 11 (11) ◽  
pp. 4877
Author(s):  
Ravneet Mandair ◽  
Pinar Karagoz ◽  
Roslyn M. Bill
Keyword(s):  
Malate Dehydrogenase ◽  
Closed System ◽  
Glucose Dehydrogenase ◽  
Sulfolobus Solfataricus ◽  
Cofactor Regeneration ◽  
Triple Mutant ◽  
Thermococcus Kodakarensis ◽  
Platform Chemicals ◽  
Enzyme Cascade

A triple mutant of NADP(H)-dependent malate dehydrogenase from thermotolerant Thermococcus kodakarensis has an altered cofactor preference for NAD+, as well as improved malate production compared to wildtype malate dehydrogenase. By combining mutant malate dehydrogenase with glucose dehydrogenase from Sulfolobus solfataricus and NAD+/NADH in a closed reaction environment, gluconate and malate could be produced from pyruvate and glucose. After 3 h, the yield of malate was 15.96 mM. These data demonstrate the feasibility of a closed system capable of cofactor regeneration in the production of platform chemicals.

scholarly journals Construction and characterization of a novel glucose dehydrogenase-leucine dehydrogenase fusion enzyme for the biosynthesis of l-tert-leucine

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Langxing Liao ◽  
Yonghui Zhang ◽  
Yali Wang ◽  
Yousi Fu ◽  
Aihui Zhang ◽  
...  
Keyword(s):  
Glucose Dehydrogenase ◽  
Catalytic Efficiency ◽  
Space Time ◽  
Cofactor Regeneration ◽  
Enzyme Complex ◽  
Regeneration System ◽  
Regeneration Rate ◽  
Leucine Dehydrogenase ◽  
Fusion Enzyme ◽  
Space Time Yield

Abstract Background Biosynthesis of l-tert-leucine (l-tle), a significant pharmaceutical intermediate, by a cofactor regeneration system friendly and efficiently is a worthful goal all the time. The cofactor regeneration system of leucine dehydrogenase (LeuDH) and glucose dehydrogenase (GDH) has showed great coupling catalytic efficiency in the synthesis of l-tle, however the multi-enzyme complex of GDH and LeuDH has never been constructed successfully. Results In this work, a novel fusion enzyme (GDH–R3–LeuDH) for the efficient biosynthesis of l-tle was constructed by the fusion of LeuDH and GDH mediated with a rigid peptide linker. Compared with the free enzymes, both the environmental tolerance and thermal stability of GDH–R3–LeuDH had a great improved since the fusion structure. The fusion structure also accelerated the cofactor regeneration rate and maintained the enzyme activity, so the productivity and yield of l-tle by GDH–R3–LeuDH was all enhanced by twofold. Finally, the space–time yield of l-tle catalyzing by GDH–R3–LeuDH whole cells could achieve 2136 g/L/day in a 200 mL scale system under the optimal catalysis conditions (pH 9.0, 30 °C, 0.4 mM of NAD+ and 500 mM of a substrate including trimethylpyruvic acid and glucose). Conclusions It is the first report about the fusion of GDH and LeuDH as the multi-enzyme complex to synthesize l-tle and reach the highest space–time yield up to now. These results demonstrated the great potential of the GDH–R3–LeuDH fusion enzyme for the efficient biosynthesis of l-tle.

scholarly journals The in vivo and in vitro substrate specificity of quinoprotein glucose dehydrogenase ofAcinetobacter calcoaceticusLMD79.41

1987 ◽  
Vol 43 (2) ◽  
pp. 195-200 ◽  
Author(s):  
P. Dokter ◽  
J.T. Pronk ◽  
B.J. Schie ◽  
J.P. Dijken ◽  
J.A. Duine
Keyword(s):  
Substrate Specificity ◽  
Glucose Dehydrogenase

Fine-tuning dirhodium compounds with bridging ligands: Synthesis, structure, catalytic efficiency

2021 ◽  
Vol 954-955 ◽  
pp. 122078
Author(s):  
Yangbo Ning ◽  
Jiantao Tan ◽  
Zhifan Wang ◽  
Yuanhua Wang
Keyword(s):  
Catalytic Efficiency ◽  
Fine Tuning ◽  
Bridging Ligands

scholarly journals Probing the Catalytic Efficiency of Supported Heteropoly Acids for Esterification: Effect of Weak Catalyst Support Interactions

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ali Alsalme ◽  
Aliyah A. Alsharif ◽  
Hamda Al-Enizi ◽  
Mujeeb Khan ◽  
Saad G. Alshammari ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Active Sites ◽  
Catalyst Support ◽  
Supported Catalyst ◽  
Catalytic Efficiency ◽  
Biodiesel Production ◽  
Effect Of Temperature ◽  
Heteropoly Acids ◽  
Catalyst Loading ◽  
Esterification Activity

Supported heteropoly acids are an interesting class of solid acid catalysts which possess flexible structure and super acidic properties essentially required for the oil-based biodiesel production. In this study, a series of catalysts containing 25 wt.% of heteropolytungstate (HPW) supported on various clays or SiO2 were prepared, and their catalytic efficiency was evaluated for esterification of acetic acid with heptanol. The as-prepared catalysts were characterized by various techniques including FT-IR spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and BET. The catalytic efficiency of both bulk and supported HPW catalysts for the esterification activity strongly depends on the type of support and amount of catalyst; the bulk HPW catalyst and the catalyst supported by kaolinite with 25 wt.% of HPW exhibited highest activity. In order to study the effect of temperature on conversion, all the catalysts were subjected to different reaction temperatures. It was revealed that esterification activity of both bulk and supported HPW catalysts strongly depends upon the temperature variations of the reaction. Besides, the effect of leaching of active sites on the catalysts performance for biodiesel production was also evaluated by inductively coupled plasma studies (ICP). The kaolinite-supported catalyst (25% HPW/kaolinite) demonstrated higher amount of leaching which is also confirmed by the significant decrease in its catalytic activity when it is used for the second time. However, the higher activity demonstrated by HPW/kaolinite maybe because of some homogeneous reaction indicating a weak catalyst support interaction (WCSI) resulting in the leaching of the catalyst during the test. Furthermore, the effects of other reaction variables such as catalyst loading and reaction time on the conversion of acetic acid were also studied.

scholarly journals Deep Learning of COVID-19 Chest X-Rays: New Models or Fine Tuning?

2020 ◽  
Author(s):  
Tuan Pham
Keyword(s):  
Deep Learning ◽  
High Performance ◽  
Data Augmentation ◽  
Dominant Role ◽  
Care Center ◽  
Characteristic Curve ◽  
Fine Tuning ◽  
Urgent Care ◽  
X Rays ◽  
Training Time

Chest X-rays have been found to be very promising for assessing COVID-19 patients, especially for resolving emergency-department and urgent-care-center overcapacity. Deep-learning (DL) methods in artificial intelligence (AI) play a dominant role as high-performance classifiers in the detection of the disease using chest X-rays. While many new DL models have been being developed for this purpose, this study aimed to investigate the fine tuning of pretrained convolutional neural networks (CNNs) for the classification of COVID-19 using chest X-rays. Three pretrained CNNs, which are AlexNet, GoogleNet, and SqueezeNet, were selected and fine-tuned without data augmentation to carry out 2-class and 3-class classification tasks using 3 public chest X-ray databases. In comparison with other recently developed DL models, the 3 pretrained CNNs achieved very high classification results in terms of accuracy, sensitivity, specificity, precision, F1 score, and area under the receiver-operating-characteristic curve. AlexNet, GoogleNet, and SqueezeNet require the least training time among pretrained DL models, but with suitable selection of training parameters, excellent classification results can be achieved without data augmentation by these networks. The findings contribute to the urgent need for harnessing the pandemic by facilitating the deployment of AI tools that are fully automated and readily available in the public domain for rapid implementation.

scholarly journals A structural and kinetic survey of GH5_4 endoglucanases reveals determinants of broad substrate specificity and opportunities for biomass hydrolysis

2020 ◽  
Vol 295 (51) ◽  
pp. 17752-17769
Author(s):  
Evan M. Glasgow ◽  
Elias I. Kemna ◽  
Craig A. Bingman ◽  
Nicole Ing ◽  
Kai Deng ◽  
...  
Keyword(s):  
Substrate Specificity ◽  
Protein Design ◽  
Plant Biomass ◽  
Catalytic Efficiency ◽  
Structural Features ◽  
Glycoside Hydrolases ◽  
Design Strategies ◽  
Biomass Hydrolysis ◽  
Diverse Range ◽  
Broad Specificity

Broad-specificity glycoside hydrolases (GHs) contribute to plant biomass hydrolysis by degrading a diverse range of polysaccharides, making them useful catalysts for renewable energy and biocommodity production. Discovery of new GHs with improved kinetic parameters or more tolerant substrate-binding sites could increase the efficiency of renewable bioenergy production even further. GH5 has over 50 subfamilies exhibiting selectivities for reaction with β-(1,4)–linked oligo- and polysaccharides. Among these, subfamily 4 (GH5_4) contains numerous broad-selectivity endoglucanases that hydrolyze cellulose, xyloglucan, and mixed-linkage glucans. We previously surveyed the whole subfamily and found over 100 new broad-specificity endoglucanases, although the structural origins of broad specificity remained unclear. A mechanistic understanding of GH5_4 substrate specificity would help inform the best protein design strategies and the most appropriate industrial application of broad-specificity endoglucanases. Here we report structures of 10 new GH5_4 enzymes from cellulolytic microbes and characterize their substrate selectivity using normalized reducing sugar assays and MS. We found that GH5_4 enzymes have the highest catalytic efficiency for hydrolysis of xyloglucan, glucomannan, and soluble β-glucans, with opportunistic secondary reactions on cellulose, mannan, and xylan. The positions of key aromatic residues determine the overall reaction rate and breadth of substrate tolerance, and they contribute to differences in oligosaccharide cleavage patterns. Our new composite model identifies several critical structural features that confer broad specificity and may be readily engineered into existing industrial enzymes. We demonstrate that GH5_4 endoglucanases can have broad specificity without sacrificing high activity, making them a valuable addition to the biomass deconstruction toolset.

Fine-tuning of the substrate binding mode to enhance the catalytic efficiency of an ortho-haloacetophenone-specific carbonyl reductase

2020 ◽  
Vol 10 (8) ◽  
pp. 2462-2472
Author(s):  
Aipeng Li ◽  
Xue Li ◽  
Wei Pang ◽  
Qing Tian ◽  
Ting Wang ◽  
...  
Keyword(s):  
Substrate Binding ◽  
Catalytic Efficiency ◽  
Binding Mode ◽  
Carbonyl Reductase ◽  
Fine Tuning

Fine-tuning of the substrate binding mode was successfully applied for enhancing the catalytic efficiency of an ortho-haloacetophenone-specific carbonyl reductase.

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