The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
David L Sibley - One of the best experts on this subject based on the ideXlab platform.
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the Aromatic Amino Acid hydroxylase genes aah1 and aah2 in toxoplasma gondii contribute to transmission in the cat
PLOS Pathogens, 2017Co-Authors: Zi T Wang, Shiv K Verma, J P Dubey, David L SibleyAbstract:The Toxoplasma gondii genome contains two Aromatic Amino Acid hydroxylase genes, AAH1 and AAH2 encode proteins that produce L-DOPA, which can serve as a precursor of catecholamine neurotransmitters. It has been suggested that this pathway elevates host dopamine levels thus making infected rodents less fearful of their definitive Felidae hosts. However, L-DOPA is also a structural precursor of melanins, secondary quinones, and dityrosine protein crosslinks, which are produced by many species. For example, dityrosine crosslinks are abundant in the oocyst walls of Eimeria and T. gondii, although their structural role has not been demonstrated, Here, we investigated the biology of AAH knockout parasites in the sexual reproductive cycle within cats. We found that ablation of the AAH genes resulted in reduced infection in the cat, lower oocyst yields, and decreased rates of sporulation. Our findings suggest that the AAH genes play a predominant role during infection in the gut of the definitive feline host.
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reassessment of the role of Aromatic Amino Acid hydroxylases and the effect of infection by toxoplasma gondii on host dopamine
Infection and Immunity, 2015Co-Authors: Zi T Wang, Steve Harmon, Karen L Omalley, David L SibleyAbstract:Toxoplasma gondii infection has been described previously to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded Aromatic Amino Acid hydroxylases. Here, we report successful knockout and complementation of the Aromatic Amino Acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two Aromatic Amino Acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was overexpressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may affect this pathway locally. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii, since AAH1 is essential for growth in nondopaminergic cells.
Zi T Wang - One of the best experts on this subject based on the ideXlab platform.
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the Aromatic Amino Acid hydroxylase genes aah1 and aah2 in toxoplasma gondii contribute to transmission in the cat
PLOS Pathogens, 2017Co-Authors: Zi T Wang, Shiv K Verma, J P Dubey, David L SibleyAbstract:The Toxoplasma gondii genome contains two Aromatic Amino Acid hydroxylase genes, AAH1 and AAH2 encode proteins that produce L-DOPA, which can serve as a precursor of catecholamine neurotransmitters. It has been suggested that this pathway elevates host dopamine levels thus making infected rodents less fearful of their definitive Felidae hosts. However, L-DOPA is also a structural precursor of melanins, secondary quinones, and dityrosine protein crosslinks, which are produced by many species. For example, dityrosine crosslinks are abundant in the oocyst walls of Eimeria and T. gondii, although their structural role has not been demonstrated, Here, we investigated the biology of AAH knockout parasites in the sexual reproductive cycle within cats. We found that ablation of the AAH genes resulted in reduced infection in the cat, lower oocyst yields, and decreased rates of sporulation. Our findings suggest that the AAH genes play a predominant role during infection in the gut of the definitive feline host.
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reassessment of the role of Aromatic Amino Acid hydroxylases and the effect of infection by toxoplasma gondii on host dopamine
Infection and Immunity, 2015Co-Authors: Zi T Wang, Steve Harmon, Karen L Omalley, David L SibleyAbstract:Toxoplasma gondii infection has been described previously to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded Aromatic Amino Acid hydroxylases. Here, we report successful knockout and complementation of the Aromatic Amino Acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two Aromatic Amino Acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was overexpressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may affect this pathway locally. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii, since AAH1 is essential for growth in nondopaminergic cells.
Zengyi Shao - One of the best experts on this subject based on the ideXlab platform.
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building microbial factories for the production of Aromatic Amino Acid pathway derivatives from commodity chemicals to plant sourced natural products
Metabolic Engineering, 2020Co-Authors: Mingfeng Cao, Miguel Suástegui, Meirong Gao, Yanzhen Mei, Zengyi ShaoAbstract:The Aromatic Amino Acid biosynthesis pathway, together with its downstream branches, represents one of the most commercially valuable biosynthetic pathways, producing a diverse range of complex molecules with many useful bioactive properties. Aromatic compounds are crucial components for major commercial segments, from polymers to foods, nutraceuticals, and pharmaceuticals, and the demand for such products has been projected to continue to increase at national and global levels. Compared to direct plant extraction and chemical synthesis, microbial production holds promise not only for much shorter cultivation periods and robustly higher yields, but also for enabling further derivatization to improve compound efficacy by tailoring new enzymatic steps. This review summarizes the biosynthetic pathways for a large repertoire of commercially valuable products that are derived from the Aromatic Amino Acid biosynthesis pathway, and it highlights both generic strategies and specific solutions to overcome certain unique problems to enhance the productivities of microbial hosts.
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Multilevel engineering of the upstream module of Aromatic Amino Acid biosynthesis in Saccharomyces cerevisiae for high production of polymer and drug precursors.
Metabolic engineering, 2017Co-Authors: Miguel Suástegui, Anupam Chowdhury, Wan Sun, Mingfeng Cao, Emma House, Costas D. Maranas, Zengyi ShaoAbstract:Abstract A multilevel approach was implemented in Saccharomyces cerevisiae to optimize the precursor module of the Aromatic Amino Acid biosynthesis pathway, which is a rich resource for synthesizing a great variety of chemicals ranging from polymer precursor, to nutraceuticals and pain-relief drugs. To facilitate the discovery of novel targets to enhance the pathway flux, we incorporated the computational tool YEASTRACT for predicting novel transcriptional repressors and OptForce strain-design for identifying non-intuitive pathway interventions. The multilevel approach consisted of (i) relieving the pathway from strong transcriptional repression, (ii) removing competing pathways to ensure high carbon capture, and (iii) rewiring precursor pathways to increase the carbon funneling to the desired target. The combination of these interventions led to the establishment of a S. cerevisiae strain with shikimic Acid (SA) titer reaching as high as 2.5 g L −1 , 7-fold higher than the base strain. Further expansion of the platform led to the titer of 2.7 g L −1 of muconic Acid (MA) and its intermediate protocatechuic Acid (PCA) together. Both the SA and MA production platforms demonstrated increases in titer and yield nearly 300% from the previously reported, highest-producing S. cerevisiae strains. Further examination elucidated the diverged impacts of disrupting the oxidative branch ( ZWF1 ) of the pentose phosphate pathway on the titers of desired products belonging to different portions of the pathway. The investigation of other non-intuitive interventions like the deletion of the Pho13 enzyme also revealed the important role of the transaldolase in determining the fate of the carbon flux in the pathways of study. This integrative approach identified novel determinants at both transcriptional and metabolic levels that constrain the flux entering the Aromatic Amino Acid pathway. In the future, this platform can be readily used for engineering the downstream modules toward the production of important plant-sourced Aromatic secondary metabolites.
Michael P Torrensspence - One of the best experts on this subject based on the ideXlab platform.
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monoamine biosynthesis via a noncanonical calcium activatable Aromatic Amino Acid decarboxylase in psilocybin mushroom
ACS Chemical Biology, 2018Co-Authors: Michael P Torrensspence, Chun-ting Liu, Tomáš Pluskal, Yin Kwan Chung, Jing-ke WengAbstract:Aromatic l-Amino Acid decarboxylases (AAADs) are a phylogenetically diverse group of enzymes responsible for the decarboxylation of Aromatic Amino Acid substrates into their corresponding Aromatic arylalkylamines. AAADs have been extensively studied in mammals and plants as they catalyze the first step in the production of neurotransmitters and bioactive phytochemicals, respectively. Unlike mammals and plants, the hallucinogenic psilocybin mushroom Psilocybe cubensis reportedly employs an unrelated phosphatidylserine-decarboxylase-like enzyme to catalyze l-tryptophan decarboxylation, the first step in psilocybin biosynthesis. To explore the origin of this chemistry in psilocybin mushroom, we generated the first de novo transcriptomes of P. cubensis and investigated several putative l-tryptophan-decarboxylase-like enzymes. We report the biochemical characterization of a noncanonical AAAD from P. cubensis ( PcncAAAD) that exhibits substrate permissiveness toward l-phenylalanine, l-tyrosine, and l-tryptophan, as well as chloro-tryptophan derivatives. The crystal structure of PcncAAAD revealed the presence of a unique C-terminal appendage domain featuring a novel double-β-barrel fold. This domain is required for PcncAAAD activity and regulates catalytic rate and thermal stability through calcium binding. PcncAAAD likely plays a role in psilocybin production in P. cubensis and offers a new tool for metabolic engineering of Aromatic-Amino-Acid-derived natural products.
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investigation of a substrate specifying residue within papaver somniferum and catharanthus roseus Aromatic Amino Acid decarboxylases
Phytochemistry, 2014Co-Authors: Michael P Torrensspence, Michael R Lazear, Renee Von Guggenberg, Haizhen DingAbstract:Plant Aromatic Amino Acid decarboxylases (AAADs) catalyze the decarboxylation of Aromatic Amino Acids with either benzene or indole rings. Because the substrate selectivity of AAADs is intimately related to their physiological functions, primary sequence data and their differentiation could provide significant physiological insights. However, due to general high sequence identity, plant AAAD substrate specificities have been difficult to identify through primary sequence comparison. In this study, bioinformatic approaches were utilized to identify several active site residues within plant AAAD enzymes that may impact substrate specificity. Next a Papaver somniferum tyrosine decarboxylase (TyDC) was selected as a model to verify our putative substrate-dictating residues through mutation. Results indicated that mutagenesis of serine 372 to glycine enables the P. somniferum TyDC to use 5-hydroxytryptophan as a substrate, and reduces the enzyme activity toward 3,4-dihydroxy-L-phenylalanine (dopa). Additionally, the reverse mutation in a Catharanthus roseus tryptophan decarboxylase (TDC) enables the mutant enzyme to utilize tyrosine and dopa as substrates with a reduced affinity toward tryptophan. Molecular modeling and molecular docking of the P. somniferum TyDC and the C. roseus TDC enzymes provided a structural basis to explain alterations in substrate specificity. Identification of an active site residue that impacts substrate selectivity produces a primary sequence identifier that may help differentiate the indolic and phenolic substrate specificities of individual plant AAADs.
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biochemical evaluation of the decarboxylation and decarboxylation deamination activities of plant Aromatic Amino Acid decarboxylases
Journal of Biological Chemistry, 2013Co-Authors: Michael P Torrensspence, Pingyang Liu, Haizhen Ding, Kim Harich, Glenda E GillaspyAbstract:Plant Aromatic Amino Acid decarboxylase (AAAD) enzymes are capable of catalyzing either decarboxylation or decarboxylation-deamination on various combinations of Aromatic Amino Acid substrates. These two different activities result in the production of arylalkylamines and the formation of Aromatic acetaldehydes, respectively. Variations in product formation enable individual enzymes to play different physiological functions. Despite these catalytic variations, arylalkylamine and aldehyde synthesizing AAADs are indistinguishable without protein expression and characterization. In this study, extensive biochemical characterization of plant AAADs was performed to identify residues responsible for differentiating decarboxylation AAADs from aldehyde synthase AAADs. Results demonstrated that a tyrosine residue located on a catalytic loop proximal to the active site of plant AAADs is primarily responsible for dictating typical decarboxylase activity, whereas a phenylalanine at the same position is primarily liable for aldehyde synthase activity. Mutagenesis of the active site phenylalanine to tyrosine in Arabidopsis thaliana and Petroselinum crispum Aromatic acetaldehyde synthases primarily converts the enzymes activity from decarboxylation-deamination to decarboxylation. The mutation of the active site tyrosine to phenylalanine in the Catharanthus roseus and Papaver somniferum Aromatic Amino Acid decarboxylases changes the enzymes decarboxylation activity to a primarily decarboxylation-deamination activity. Generation of these mutant enzymes enables the production of unusual AAAD enzyme products including indole-3-acetaldehyde, 4-hydroxyphenylacetaldehyde, and phenylethylamine. Our data indicates that the tyrosine and phenylalanine in the catalytic loop region could serve as a signature residue to reliably distinguish plant arylalkylamine and aldehyde synthesizing AAADs. Additionally, the resulting data enables further insights into the mechanistic roles of active site residues.
Emily J Parker - One of the best experts on this subject based on the ideXlab platform.
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tyrosine latching of a regulatory gate affords allosteric control of Aromatic Amino Acid biosynthesis
Journal of Biological Chemistry, 2011Co-Authors: Penelope J Cross, Renwick C J Dobson, Mark L Patchett, Emily J ParkerAbstract:The first step of the shikimate pathway for Aromatic Amino Acid biosynthesis is catalyzed by 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS). Thermotoga maritima DAH7PS (TmaDAH7PS) is tetrameric, with monomer units comprised of a core catalytic (β/α)8 barrel and an N-terminal domain. This enzyme is inhibited strongly by tyrosine and to a lesser extent by the presence of phenylalanine. A truncated mutant of TmaDAH7PS lacking the N-terminal domain was catalytically more active and completely insensitive to tyrosine and phenylalanine, consistent with a role for this domain in allosteric inhibition. The structure of this protein was determined to 2.0 Å. In contrast to the wild-type enzyme, this enzyme is dimeric. Wild-type TmaDAH7PS was co-crystallized with tyrosine, and the structure of this complex was determined to a resolution of 2.35 Å. Tyrosine was found to bind at the interface between two regulatory N-terminal domains, formed from diagonally located monomers of the tetramer, revealing a major reorganization of the regulatory domain with respect to the barrel relative to unliganded enzyme. This significant conformational rearrangement observed in the crystal structures was also clearly evident from small angle X-ray scattering measurements recorded in the presence and absence of tyrosine. The closed conformation adopted by the protein on tyrosine binding impedes substrate entry into the neighboring barrel, revealing an unusual tyrosine-controlled gating mechanism for allosteric control of this enzyme.
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synergistic allostery a sophisticated regulatory network for the control of Aromatic Amino Acid biosynthesis in mycobacterium tuberculosis
Journal of Biological Chemistry, 2010Co-Authors: Celia J Webby, Wanting Jiao, Richard D Hutton, Nicola J Blackmore, Heather M Baker, Edward N Baker, Geoffrey B Jameson, Emily J ParkerAbstract:The shikimate pathway, responsible for Aromatic Amino Acid biosynthesis, is required for the growth of Mycobacterium tuberculosis and is a potential drug target. The first reaction is catalyzed by 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS). Feedback regulation of DAH7PS activity by Aromatic Amino Acids controls shikimate pathway flux. Whereas Mycobacterium tuberculosis DAH7PS (MtuDAH7PS) is not inhibited by the addition of Phe, Tyr, or Trp alone, combinations cause significant loss of enzyme activity. In the presence of 200 μm Phe, only 2.4 μm Trp is required to reduce enzymic activity to 50%. Reaction kinetics were analyzed in the presence of inhibitory concentrations of Trp/Phe or Trp/Tyr. In the absence of inhibitors, the enzyme follows Michaelis-Menten kinetics with respect to substrate erythrose 4-phosphate (E4P), whereas the addition of inhibitor combinations caused significant homotropic cooperativity with respect to E4P, with Hill coefficients of 3.3 (Trp/Phe) and 2.8 (Trp/Tyr). Structures of MtuDAH7PS/Trp/Phe, MtuDAH7PS/Trp, and MtuDAH7PS/Phe complexes were determined. The MtuDAH7PS/Trp/Phe homotetramer binds four Trp and six Phe molecules. Binding sites for both Aromatic Amino Acids are formed by accessory elements to the core DAH7PS (β/α)8 barrel that are unique to the type II DAH7PS family and contribute to the tight dimer and tetramer interfaces. A comparison of the liganded and unliganded MtuDAH7PS structures reveals changes in the interface areas associated with inhibitor binding and a small displacement of the E4P binding loop. These studies uncover a previously unrecognized mode of control for the branched pathways of Aromatic Amino Acid biosynthesis involving synergistic inhibition by specific pairs of pathway end products.