The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
Xiulai Chen - One of the best experts on this subject based on the ideXlab platform.
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fumarate production by torulopsis glabrata engineering heterologous fumarase expression and improving acid tolerance
PLOS ONE, 2016Co-Authors: Xiulai Chen, Wei SongAbstract:: Fumarate is a well-known biomass building block compound. However, the poor catalytic efficiency of fumarase is one of the major factors preventing its widespread production. To address this issue, we selected residues 159HPND162 of fumarase from Rhizopus oryzae as targets for site-directed mutagenesis based on molecular docking analysis. Twelve mutants were generated and characterized in detail. Kinetic studies showed that the Km values of the P160A, P160T, P160H, N161E, and D162W mutants were decreased, whereas Km values of H159Y, H159V, H159S, N161R, N161F, D162K, and D162M mutants were increased. In addition, all mutants displayed decreased catalytic efficiency except for the P160A mutant, whose kcat/Km was increased by 33.2%. Moreover, by overexpressing the P160A mutant, the engineered strain T.G-PMS-P160A was able to produce 5.2 g/L fumarate. To further enhance fumarate production, the acid tolerance of T.G-PMS-P160A was improved by deleting ade12, a component of the Purine Nucleotide Cycle, and the resulting strain T.G(△ade12)-PMS-P160A produced 9.2 g/L fumarate. The strategy generated in this study opens up new avenues for pathway optimization and efficient production of natural products.
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fumaric acid production by torulopsis glabrata engineering the urea Cycle and the Purine Nucleotide Cycle
Biotechnology and Bioengineering, 2015Co-Authors: Xiulai Chen, Limei Zhang, Jing Wu, Wei Song, Hongjiang WangAbstract:A multi-vitamin auxotrophic Torulopsis glabrata strain, a pyruvate producer, was further engineered to produce fumaric acid. Using the genome-scale metabolic model iNX804 of T. glabrata, four fumaric acid biosynthetic pathways, involving the four cytosolic enzymes, argininosuccinate lyase (ASL), adenylosuccinate lyase (ADSL), fumarylacetoacetase (FAA), and fumarase (FUM1), were found. Athough single overexpression of each of the four enzymes in the cytosol improved fumaric acid production, the highest fumaric acid titer (5.62 g L−1) was obtained with strain T.G-ASL(H)-ADSL(L) by controlling the strength of ASL at a high level and ADSL at a low level. In order to further improve the production of fumaric acid, the SpMAE1 gene encoding the C4-dicarboxylic acids transporter was overexpressed in strain T.G-ASL(H)-ADSL(L)-SpMAE1 and the final fumaric acid titer increased to 8.83 g L−1. This study provides a novel strategy for fumaric acid biosynthesis by utilizing the urea Cycle and the Purine Nucleotide Cycle to enhance the bridge between carbon metabolism and nitrogen metabolism. Biotechnol. Bioeng. 2015;112: 156–167. © 2014 Wiley Periodicals, Inc.
Wei Song - One of the best experts on this subject based on the ideXlab platform.
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fumarate production by torulopsis glabrata engineering heterologous fumarase expression and improving acid tolerance
PLOS ONE, 2016Co-Authors: Xiulai Chen, Wei SongAbstract:: Fumarate is a well-known biomass building block compound. However, the poor catalytic efficiency of fumarase is one of the major factors preventing its widespread production. To address this issue, we selected residues 159HPND162 of fumarase from Rhizopus oryzae as targets for site-directed mutagenesis based on molecular docking analysis. Twelve mutants were generated and characterized in detail. Kinetic studies showed that the Km values of the P160A, P160T, P160H, N161E, and D162W mutants were decreased, whereas Km values of H159Y, H159V, H159S, N161R, N161F, D162K, and D162M mutants were increased. In addition, all mutants displayed decreased catalytic efficiency except for the P160A mutant, whose kcat/Km was increased by 33.2%. Moreover, by overexpressing the P160A mutant, the engineered strain T.G-PMS-P160A was able to produce 5.2 g/L fumarate. To further enhance fumarate production, the acid tolerance of T.G-PMS-P160A was improved by deleting ade12, a component of the Purine Nucleotide Cycle, and the resulting strain T.G(△ade12)-PMS-P160A produced 9.2 g/L fumarate. The strategy generated in this study opens up new avenues for pathway optimization and efficient production of natural products.
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fumaric acid production by torulopsis glabrata engineering the urea Cycle and the Purine Nucleotide Cycle
Biotechnology and Bioengineering, 2015Co-Authors: Xiulai Chen, Limei Zhang, Jing Wu, Wei Song, Hongjiang WangAbstract:A multi-vitamin auxotrophic Torulopsis glabrata strain, a pyruvate producer, was further engineered to produce fumaric acid. Using the genome-scale metabolic model iNX804 of T. glabrata, four fumaric acid biosynthetic pathways, involving the four cytosolic enzymes, argininosuccinate lyase (ASL), adenylosuccinate lyase (ADSL), fumarylacetoacetase (FAA), and fumarase (FUM1), were found. Athough single overexpression of each of the four enzymes in the cytosol improved fumaric acid production, the highest fumaric acid titer (5.62 g L−1) was obtained with strain T.G-ASL(H)-ADSL(L) by controlling the strength of ASL at a high level and ADSL at a low level. In order to further improve the production of fumaric acid, the SpMAE1 gene encoding the C4-dicarboxylic acids transporter was overexpressed in strain T.G-ASL(H)-ADSL(L)-SpMAE1 and the final fumaric acid titer increased to 8.83 g L−1. This study provides a novel strategy for fumaric acid biosynthesis by utilizing the urea Cycle and the Purine Nucleotide Cycle to enhance the bridge between carbon metabolism and nitrogen metabolism. Biotechnol. Bioeng. 2015;112: 156–167. © 2014 Wiley Periodicals, Inc.
Hongjiang Wang - One of the best experts on this subject based on the ideXlab platform.
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fumaric acid production by torulopsis glabrata engineering the urea Cycle and the Purine Nucleotide Cycle
Biotechnology and Bioengineering, 2015Co-Authors: Xiulai Chen, Limei Zhang, Jing Wu, Wei Song, Hongjiang WangAbstract:A multi-vitamin auxotrophic Torulopsis glabrata strain, a pyruvate producer, was further engineered to produce fumaric acid. Using the genome-scale metabolic model iNX804 of T. glabrata, four fumaric acid biosynthetic pathways, involving the four cytosolic enzymes, argininosuccinate lyase (ASL), adenylosuccinate lyase (ADSL), fumarylacetoacetase (FAA), and fumarase (FUM1), were found. Athough single overexpression of each of the four enzymes in the cytosol improved fumaric acid production, the highest fumaric acid titer (5.62 g L−1) was obtained with strain T.G-ASL(H)-ADSL(L) by controlling the strength of ASL at a high level and ADSL at a low level. In order to further improve the production of fumaric acid, the SpMAE1 gene encoding the C4-dicarboxylic acids transporter was overexpressed in strain T.G-ASL(H)-ADSL(L)-SpMAE1 and the final fumaric acid titer increased to 8.83 g L−1. This study provides a novel strategy for fumaric acid biosynthesis by utilizing the urea Cycle and the Purine Nucleotide Cycle to enhance the bridge between carbon metabolism and nitrogen metabolism. Biotechnol. Bioeng. 2015;112: 156–167. © 2014 Wiley Periodicals, Inc.
Stanislav Kmoch - One of the best experts on this subject based on the ideXlab platform.
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D-ribose therapy in four Polish patients with adenylosuccinate lyase deficiency: absence of positive effect.
Journal of inherited metabolic disease, 2008Co-Authors: Agnieszka Jurecka, Marie Zikanova, Anna Tylki-szymańska, Jakub Krijt, Stanislav KmochAbstract:Deficiency of adenylosuccinate lyase (ADSL) (OMIM 103050) is an autosomal recessive disorder of the Purine de novo synthesis pathway and Purine Nucleotide Cycle, diagnosed so far in approximately 50 patients. The clinical presentation is characterized by severe neurological involvement including hypotonia, seizures, developmental delay and autistic features. Epilepsy in ADSL deficiency is frequent and occurs in approximately two-thirds of patients, beginning either early in the neonatal period or after the first year of life. At present there is no treatment of proven clinical efficacy. Despite of the increasing number of ADSL-deficient patients reported, there are only a few communications of therapeutic considerations or efforts. Among them only two showed some beneficial effects in ADSL-deficient patients. D-ribose, a simple and relatively cheap therapy, has been associated with improvement of behaviour and progressive reduction of the seizure frequency in one 13-year-old patient with ADSL deficiency. In this study we have re-examined D-ribose treatment in four ADSL-deficient patients. Assessments consisted of biochemical markers and neurological outcome. The 12-month trial of D-ribose failed to show any clinical benefit in ADSL patients with both milder and severe phenotype. D-ribose administration was accompanied by neither reduction in seizure frequency nor growth enhancement. Additionally, patients with milder type II presented the first seizure after 4 and 8 months of the D-ribose treatment. Therefore, we could not confirm a positive effect of D-ribose as previously reported.
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Clinical, biochemical and molecular findings in seven Polish patients with adenylosuccinate lyase deficiency.
Molecular genetics and metabolism, 2008Co-Authors: Agnieszka Jurecka, Marie Zikanova, Stanislav Kmoch, Anna Tylki-szymańska, Jakub Krijt, Anna Bogdanska, Wanda Gradowska, Karolina Mullerova, Jolanta Sykut-cegielska, Ewa PronickaAbstract:Abstract Adenylosuccinate lyase (ADSL) catalyzes two steps in Purine Nucleotide metabolism—the 8th step in the de novo pathway: conversion of succinylaminoimidazole carboxamide ribotide (SAICAR) to aminoimidazole carboxamide ribotide (AICAR), and conversion of adenylosuccinate (S-AMP) to adenylate (AMP) in the Purine Nucleotide Cycle. To date, over 50 patients have been reported suffering from ADSL deficiency. We report all seven so far diagnosed Polish patients with this defect. Most of our patients shared intractable seizures and psychomotor retardation since the neonatal period and had biochemical evidence of severe (type I) deficiency. Two patients with type II suffered only from mild/moderate psychomotor retardation and showed a transientvisual contact disturbance. One patient had a fatal neonatal form of ADSL deficiency with lack of spontaneous movement, respiratory failure, severe encephalopathy and intractable seizures. Analysis of the ADSL gene showed that four apparently unrelated patients carried a R426H mutation (two homozygous and two compound heterozygous). With the exception of the latter mutation, a Y114H mutation that had been reported previously, and a novel mutation T242I, all other mutations (including D268H and three novel S23R, D215H and I351T mutations) were found only in single families in single alleles. A search for this disorder should be included in the screening program of all infants with unexplained neonatal seizures, severe infantile epileptic encephalopathy, developmental delay, hypotonia, and/or autistic features.
G Van Den Berghe - One of the best experts on this subject based on the ideXlab platform.
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Muscle Purine Nucleotide Cycle enzymes in exercise intolerance.
Advances in Experimental Medicine and Biology, 1998Co-Authors: Maria-grazia Operti, M.-françoise Vincent, Jean-marie Brucher, G Van Den BergheAbstract:Three enzymes of adenine Nucleotide metabolism, adenylosuccinate synthetase (ASS), adenylosuccinate lyase (adenylosuccinase, ASL), and AMP deaminase (AMPDA), form the Purine Nucleotide Cycle.1,2 Deficiences of muscle AMPDA (often called myoadenylate deaminase in the clinical literature) are frequently diagnosed either as a primary genetic, or as a secundary defect in patients presenting with muscular symptoms.3,5 In contrast, very few patient studies have been devoted to the two other enzymes of the Purine Nucleotide Cycle. Only Kar and Pearson6 reported normal activities of ASL in muscle from patients with Duchenne and other neuromuscular diseases. In the present study ASS, ASL, and AMPDA were assayed in a series of muscle biopsies taken from patients suffering from fatigue and cramps following moderate to vigorous exercise.
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The Purine Nucleotide Cycle and its molecular defects
Progress in Neurobiology, 1992Co-Authors: G Van Den Berghe, Françoise Bontemps, Marie-françoise Vincent, F Van Den BerghAbstract:Three enzymes of Purine metabolism, adenylosuccinate synthetase, adenylosuccinate lyase and AMP deaminase, have been proposed to form a functional unit, termed the Purine Nucleotide Cycle. This Cycle converts AMP into IMP and reconverts IMP into AMP via adenylosuccinate, thereby producing NH3 and forming fumarate from aspartate. In muscle, the Purine Nucleotide Cycle has been shown to function during intense exercise; the metabolic flux through the Cycle has been proposed to play a role in the regeneration of ATP by pulling the adenylate kinase reaction in the direction of formation of ATP, and by providing Krebs Cycle intermediates. In kidney, the Purine Nucleotide Cycle was shown to account for the release of NH3 under the normal acid-base status, but not under acidotic conditions. In brain, the Purine Nucleotide Cycle might function under conditions that induce a loss of ATP, and thereby contribute to its recovery. There is no evidence that the Purine Nucleotide Cycle operates in liver. Deficiency of muscle AMP deaminase is an apparently frequent disorder, which might affect approximately 2% of the general population. The observation that it can be found in clinically asymptomatic individuals suggests, paradoxically, that the ATP-regenerating function which has been attributed to the Purine Nucleotide Cycle is not essential for muscle function. Further work should be aimed at identifying the conditions under which AMP deaminase deficiency becomes symptomatic. Adenylosuccinate lyase deficiency provokes psychomotor retardation, often accompanied by autistic features. Its clinical heterogeneity justifies systematic screening in patients with unexplained mental deficiency. Additional studies are required to determine the mechanisms whereby this enzyme defect results in psychomotor retardation.
