The Experts below are selected from a list of 120 Experts worldwide ranked by ideXlab platform
Pascal Bonnarme - One of the best experts on this subject based on the ideXlab platform.
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Evidence for distinct L-methionine catabolic pathways in the yeast Geotrichum candidum and the bacterium Brevibacterium linens
Applied and Environmental Microbiology, 2006Co-Authors: K Arfi, Sophie Landaud, Pascal BonnarmeAbstract:Tracing experiments were carried out to identify volatile and nonvolatile L-methionine degradation intermediates and end products in the yeast Geotrichum candidum and in the bacterium Brevibacterium linens, both of which are present in the surface flora of certain soft cheeses and contribute to the ripening reactions. Since the Acid-sensitive bacterium B. linens is known to produce larger amounts and a greater variety of volatile sulfur compounds (VSCs) than the yeast G. candidum produces, we examined whether the L-methionine degradation routes of these microorganisms differ. In both microorganisms, methanethiol and alpha-ketobutyrate are generated; the former compound is the precursor of other VSCs, and the latter is subsequently degraded to 2,3-pentanedione, which has not been described previously as an end product of L-methionine catabolism. However, the L-methionine degradation pathways differ in the first steps of L-methionine degradation. L-Methionine degradation is initiated by a one-step degradation process in the bacterium B. linens, whereas a two-step degradation pathway with 4-methylthio-2-Oxobutyric Acid (MOBA) and 4-methylthio-2-hydroxybutyric Acid (MHBA) as intermediates is used in the yeast G. candidum. Since G. candidum develops earlier than B. linens during the ripening process, MOBA and MHBA generated by G.candidum could also be used as precursors for VSC production by B. linens.
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Involvment of a Branched-Chain Aminotransferase in Production of Volatile sulfur compounds in Yarrowia lipolytica
Applied and Environmental Microbiology, 2005Co-Authors: Daniela Cernat-bondar, Jean Marie Beckerich, Pascal BonnarmeAbstract:The enzymatic degradation of L-methionine and the subsequent formation of volatile sulfur compounds (VSCs) are essential for the development of the typical flavor in cheese. In the yeast Yarrowia lipolytica, the degradation of L-methionine was accompanied by the formation of the transamination product 4-methylthio-2-Oxobutyric Acid. A branched-chain aminotransferase gene (YlBCA1) of Y. lipolytica was amplified, and the L-methionine-degrading activity and the aminotransferase activity were measured in a genetically modified strain and compared to those of the parental strain. Our work shows that L-methionine degradation via transamination is involved in formation of VSCs in Y. lipolytica.
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catabolism of volatile sulfur compounds precursors by brevibacterium linens and geotrichum candidum two microorganisms of the cheese ecosystem
Journal of Biotechnology, 2003Co-Authors: K Arfi, Henryeric Spinnler, Felix Amarita, Pascal BonnarmeAbstract:Two Brevibacterium linensstrains and the cheese-ripening yeast Geotrichum candidumwere compared with regard to their ability to produce volatile sulfur compounds (VSCs) from three different precursors namely l-methionine, 4-methylthio-2-Oxobutyric Acid (KMBA) and 4-methylthio-2-hydroxybutyric Acid (HMBA). All microorganisms were able to convert these precursors to VSCs. However, although all were able to produce VSCs from l-methionine, only G. candidumaccumulated KMBA when cultivated on this amino Acid, contrary to B. linens suggesting that the transamination pathway is not active in this microorganism. Conversely, a l-methionine -lyase activity—which catalyses the one step l-methionine to methanethiol (MTL) degradation route—was only found in B. linens strains. Several other enzymatic activities involved in the catabolism of the precursors tested were investigated. KMBA transiently accumulated in G. candidum cultures, and was then reduced to HMBA by a KMBA dehydrogenase (KDH) activity. This activity was not detected in B. linens. Despite no HMBA dehydrogenase (HDH) was found in G. candidum, a strong HMBA oxidase (HOX) activity was measured in this microorganism. This latter activity was weakly active in B. linens. KMBA and HMBA demethiolating activities were found in all the microorganisms. Our results illustrate the metabolic diversity between cheese-ripening microorganisms of the cheese ecosystem. © 2003 Elsevier B.V. All rights reserved.
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sulfur compound production by geotrichum candidum from l methionine importance of the transamination step
Fems Microbiology Letters, 2001Co-Authors: Pascal Bonnarme, K Arfi, Ca Cile Dury, Sandra Helinck, Mireille Yvon, Henryeric SpinnlerAbstract:l-Methionine degradation products and catabolic enzymatic activities involved in methanethiol generation were investigated in Geotrichum candidum GcG. l-Methionine was easily degraded by G. candidum and the transamination product, 4-methylthio-2-Oxobutyric Acid (KMBA), was found to transiently accumulate. In parallel, considerable l-methionine aminotransferase activity was found in this microorganism. l-Methionine and KMBA demethiolating activities were also detected. The degradation of KMBA corresponded to an overall increase in the production of volatile sulfur compounds. These results show that the transamination pathway is of major importance in the initial breakdown of l-methionine by this cheese-ripening microorganism.
Zhiming Rao - One of the best experts on this subject based on the ideXlab platform.
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relieving allosteric inhibition by designing active inclusion bodies and coating of the inclusion bodies with fe3o4 nanomaterials for sustainable 2 Oxobutyric Acid production
ACS Catalysis, 2018Co-Authors: Junping Zhou, Rongzhen Zhang, Taowei Yang, Qiaoli Liu, Junxian Zheng, Fang Wang, Fei Liu, Xian Zhang, Zhiming RaoAbstract:Allosteric inhibition of key enzymes by the end product has been widely studied in the control of valuable compound biosynthesis, and site-directed mutagenesis is often applied for relieving allost...
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Relieving Allosteric Inhibition by Designing Active Inclusion Bodies and Coating of the Inclusion Bodies with Fe3O4 Nanomaterials for Sustainable 2‑Oxobutyric Acid Production
2018Co-Authors: Junping Zhou, Rongzhen Zhang, Taowei Yang, Qiaoli Liu, Junxian Zheng, Fang Wang, Fei Liu, Xian Zhang, Zhiming RaoAbstract:Allosteric inhibition of key enzymes by the end product has been widely studied in the control of valuable compound biosynthesis, and site-directed mutagenesis is often applied for relieving allosteric inhibition. Here we rationally designed a different approach to relieve allosteric inhibition by Ile in a threonine deaminase (TD) pathway and efficiently produced 2-Oxobutyric Acid in an energy-saving way. We truncated the different peptide lengths at the C-terminal regulatory domain (from residues 11 to 193) of Escherichia coli TD and obtained the active inclusion bodies. The truncated residues Glu480–Gly514 in the C-terminal regulatory domain were confirmed to be an unstable structure by MD simulations. The truncation variants Δ11, Δ25, and Δ35 were not allosterically regulated by Ile at all by kinetics analysis. They showed decreased activity but better thermostability than wild-type enzyme. Among the three variants, Δ25 showed 3.3-fold higher 2-Oxobutyric Acid production in the presence of 2 mM Ile and about 9-fold higher production at 55 °C in comparison to the wild type. The inclusion bodies resulting from the aggregation of truncated TD dimers by hydrophobic interaction could resist the binding of Ile, as determined by calorimetry experiments. According to attenuated total reflection FTIR measurements, the inclusion bodies kept a secondary structure composition similar to that of the wild-type enzyme. Furthermore, by nonspecific adsorption of Fe3O4 nanoparticles onto inclusion bodies, they could be quickly recycled without enzyme leakage using energy-saving magnetic separation. Since many allosteric enzymes show a structure similar to that of TD, our work provides a general and effective strategy for relieving enzymatic allosteric inhibition by end products and realizes sustainable chemical production using Fe3O4 nanoparticles for inclusion body immobilization
Junping Zhou - One of the best experts on this subject based on the ideXlab platform.
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relieving allosteric inhibition by designing active inclusion bodies and coating of the inclusion bodies with fe3o4 nanomaterials for sustainable 2 Oxobutyric Acid production
ACS Catalysis, 2018Co-Authors: Junping Zhou, Rongzhen Zhang, Taowei Yang, Qiaoli Liu, Junxian Zheng, Fang Wang, Fei Liu, Xian Zhang, Zhiming RaoAbstract:Allosteric inhibition of key enzymes by the end product has been widely studied in the control of valuable compound biosynthesis, and site-directed mutagenesis is often applied for relieving allost...
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Relieving Allosteric Inhibition by Designing Active Inclusion Bodies and Coating of the Inclusion Bodies with Fe3O4 Nanomaterials for Sustainable 2‑Oxobutyric Acid Production
2018Co-Authors: Junping Zhou, Rongzhen Zhang, Taowei Yang, Qiaoli Liu, Junxian Zheng, Fang Wang, Fei Liu, Xian Zhang, Zhiming RaoAbstract:Allosteric inhibition of key enzymes by the end product has been widely studied in the control of valuable compound biosynthesis, and site-directed mutagenesis is often applied for relieving allosteric inhibition. Here we rationally designed a different approach to relieve allosteric inhibition by Ile in a threonine deaminase (TD) pathway and efficiently produced 2-Oxobutyric Acid in an energy-saving way. We truncated the different peptide lengths at the C-terminal regulatory domain (from residues 11 to 193) of Escherichia coli TD and obtained the active inclusion bodies. The truncated residues Glu480–Gly514 in the C-terminal regulatory domain were confirmed to be an unstable structure by MD simulations. The truncation variants Δ11, Δ25, and Δ35 were not allosterically regulated by Ile at all by kinetics analysis. They showed decreased activity but better thermostability than wild-type enzyme. Among the three variants, Δ25 showed 3.3-fold higher 2-Oxobutyric Acid production in the presence of 2 mM Ile and about 9-fold higher production at 55 °C in comparison to the wild type. The inclusion bodies resulting from the aggregation of truncated TD dimers by hydrophobic interaction could resist the binding of Ile, as determined by calorimetry experiments. According to attenuated total reflection FTIR measurements, the inclusion bodies kept a secondary structure composition similar to that of the wild-type enzyme. Furthermore, by nonspecific adsorption of Fe3O4 nanoparticles onto inclusion bodies, they could be quickly recycled without enzyme leakage using energy-saving magnetic separation. Since many allosteric enzymes show a structure similar to that of TD, our work provides a general and effective strategy for relieving enzymatic allosteric inhibition by end products and realizes sustainable chemical production using Fe3O4 nanoparticles for inclusion body immobilization
Shengyuan Chang - One of the best experts on this subject based on the ideXlab platform.
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immobilization of d amino Acid oxidase via a biomimetic coating and its application for the production of 4 methylthio 2 Oxobutyric Acid
Journal of The Taiwan Institute of Chemical Engineers, 2017Co-Authors: Iching Kuan, Singyu Chen, Shengyuan ChangAbstract:Abstract In this study, magnetic nanoparticles superficially modified with polydopamine were used for the immobilization of d -amino Acid oxidases from Rhodosporidium toruloides (RtDAO) and Trigonopsis variabilis (TvDAO) . The thermal and oxidative stabilities of RtDAO were improved significantly after immobilization; the T m value was increased by 11 °C and the half-life in the presence of 10 mM hydrogen peroxide was increased by 42 min. However, in the case of TvDAO, these improvements in stability were not observed. The activities of immobilized RtDAO and TvDAO were lowered to approximately 50% after sixteen and five repeated operations, respectively, indicating that the former had better reusability. Immobilized TvDAO was further applied to the conversion of d -methionine to 4-methylthio-2-Oxobutyric Acid (MTOB). Without the addition of catalase, most MTOB produced was spontaneously oxidized to 3-methylthiopropionic Acid by hydrogen peroxide. With the addition of 1600 U of catalase, the conversion reached 100% after a 10 min-incubation with the product entirely in the form of MTOB.
K Arfi - One of the best experts on this subject based on the ideXlab platform.
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Evidence for distinct L-methionine catabolic pathways in the yeast Geotrichum candidum and the bacterium Brevibacterium linens
Applied and Environmental Microbiology, 2006Co-Authors: K Arfi, Sophie Landaud, Pascal BonnarmeAbstract:Tracing experiments were carried out to identify volatile and nonvolatile L-methionine degradation intermediates and end products in the yeast Geotrichum candidum and in the bacterium Brevibacterium linens, both of which are present in the surface flora of certain soft cheeses and contribute to the ripening reactions. Since the Acid-sensitive bacterium B. linens is known to produce larger amounts and a greater variety of volatile sulfur compounds (VSCs) than the yeast G. candidum produces, we examined whether the L-methionine degradation routes of these microorganisms differ. In both microorganisms, methanethiol and alpha-ketobutyrate are generated; the former compound is the precursor of other VSCs, and the latter is subsequently degraded to 2,3-pentanedione, which has not been described previously as an end product of L-methionine catabolism. However, the L-methionine degradation pathways differ in the first steps of L-methionine degradation. L-Methionine degradation is initiated by a one-step degradation process in the bacterium B. linens, whereas a two-step degradation pathway with 4-methylthio-2-Oxobutyric Acid (MOBA) and 4-methylthio-2-hydroxybutyric Acid (MHBA) as intermediates is used in the yeast G. candidum. Since G. candidum develops earlier than B. linens during the ripening process, MOBA and MHBA generated by G.candidum could also be used as precursors for VSC production by B. linens.
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catabolism of volatile sulfur compounds precursors by brevibacterium linens and geotrichum candidum two microorganisms of the cheese ecosystem
Journal of Biotechnology, 2003Co-Authors: K Arfi, Henryeric Spinnler, Felix Amarita, Pascal BonnarmeAbstract:Two Brevibacterium linensstrains and the cheese-ripening yeast Geotrichum candidumwere compared with regard to their ability to produce volatile sulfur compounds (VSCs) from three different precursors namely l-methionine, 4-methylthio-2-Oxobutyric Acid (KMBA) and 4-methylthio-2-hydroxybutyric Acid (HMBA). All microorganisms were able to convert these precursors to VSCs. However, although all were able to produce VSCs from l-methionine, only G. candidumaccumulated KMBA when cultivated on this amino Acid, contrary to B. linens suggesting that the transamination pathway is not active in this microorganism. Conversely, a l-methionine -lyase activity—which catalyses the one step l-methionine to methanethiol (MTL) degradation route—was only found in B. linens strains. Several other enzymatic activities involved in the catabolism of the precursors tested were investigated. KMBA transiently accumulated in G. candidum cultures, and was then reduced to HMBA by a KMBA dehydrogenase (KDH) activity. This activity was not detected in B. linens. Despite no HMBA dehydrogenase (HDH) was found in G. candidum, a strong HMBA oxidase (HOX) activity was measured in this microorganism. This latter activity was weakly active in B. linens. KMBA and HMBA demethiolating activities were found in all the microorganisms. Our results illustrate the metabolic diversity between cheese-ripening microorganisms of the cheese ecosystem. © 2003 Elsevier B.V. All rights reserved.
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sulfur compound production by geotrichum candidum from l methionine importance of the transamination step
Fems Microbiology Letters, 2001Co-Authors: Pascal Bonnarme, K Arfi, Ca Cile Dury, Sandra Helinck, Mireille Yvon, Henryeric SpinnlerAbstract:l-Methionine degradation products and catabolic enzymatic activities involved in methanethiol generation were investigated in Geotrichum candidum GcG. l-Methionine was easily degraded by G. candidum and the transamination product, 4-methylthio-2-Oxobutyric Acid (KMBA), was found to transiently accumulate. In parallel, considerable l-methionine aminotransferase activity was found in this microorganism. l-Methionine and KMBA demethiolating activities were also detected. The degradation of KMBA corresponded to an overall increase in the production of volatile sulfur compounds. These results show that the transamination pathway is of major importance in the initial breakdown of l-methionine by this cheese-ripening microorganism.
