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Structure and Biosynthesis of Lignin
Published in Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel, Hemicelluloses and Lignin in Biorefineries, 2017
Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel
In plants, chorismate is a common precursor of at least four branches of metabolic pathways leading to the formation of Trp, Phe/Tyr, salicylate/phylloquinone, and folate.10 Four enzymes catalyze the committed step of the respective pathways and compete for chorismate. The Trp pathway converts chorismate to Trp via six enzymatic reactions. In contrast to the Trp pathway, the knowledge of the plant Phe and Tyr pathways is still in its infancy. In the first step of the pathways, chorismate is converted by chorismate mutase (CM) to prephenate, of which subsequent conversion to Phe and Tyr may occur via two alternative pathways. In one route (the arogenate pathway), prephenate is first transaminated to L-arogenate followed by dehydration/decarboxylation to Phe or dehydrogenation/decarboxylation to Tyr. In the other route (the phenylpyruvate or 4-hydroxyphenylpyruvate pathway), these reactions occur in reverse order. Recent genetic evidence indicates that the arogenate pathway is the predominant route for Phe biosynthesis in plants.
New mechanistic insights into the Claisen rearrangement of chorismate – a Unified Reaction Valley Approach study
Published in Molecular Physics, 2019
Marek Freindorf, Yunwen Tao, Daniel Sethio, Dieter Cremer, Elfi Kraka
The Bacillus subtilis chorismate mutase (BsCM) catalysed intramolecular Claisen rearrangement of chorismate (1) to prephenate (3) (see Figure 1) is one of the few pericyclic processes in biology [1–3]. It is an important part of the shikimate pathway controlling the biosynthesis of aromatic amino acids (e.g. tryptophan, tyrosine, and phenylalanine) in the cells of fungi, bacteria and higher plants [4–7], and as such has become one of the most studied enzyme reactions [8–32]. The theoretical interest in the BsCM-catalysed chorismate rearrangement was triggered by the fact that (i) the substrate does not covalently bind to the active site [33–35] so that the system can be easily separated into a QM region (the substrate) and an MM region (the enzyme); and (ii) the wealth of experimental data available to cross-check the reliability of the computational studies [2, 36–45].
Synthesis and evaluation of antimicrobial, antitubercular and anticancer activities of benzimidazole derivatives
Published in Egyptian Journal of Basic and Applied Sciences, 2018
Snehlata Yadav, Balasubramanian Narasimhan, Siong Meng Lim, Kalavathy Ramasamy, Mani Vasudevan, Syed Adnan Ali Shah, Abhishek Mathur
Tuberculosis (TB), caused by Mycobacterium tuberculosis (M. tuberculosis), remains a pivotal cause of high mortality worldwide despite the handiness of highly potent antitubercular drugs due to the development of resistance by the mycobacterium as a result of gene mutation to first-line antitubercular drugs [5]. To combat the mycobacterial resistance, there is a need to identify novel targets unique to M. tuberculosis which are absent in humans whose blockage would either prove lethal to the bacterium or render it extremely susceptible to the host immune response [6]. Chorismate mutase (CM), isocitrate lyase (ICL), and pantothenate synthetase (PS) are few such unique targets for M. tuberculosis [7]. Chorismate is a precursor of important molecules such folic acid, menaquinones, mycobactins and aromatic amino acids. The shikimate pathway utilizes CM as one of the key enzymes for catalyzing the isomerization of chorismate to prephenate for biosynthesis of l-phenylalanine and l-tyrosine in the mycobacteria [8,9] . The glyoxylate metabolism shunt employs ICL as an important enzyme in the main metabolic route for the biosynthesis of cellular material i.e., fatty acids, which might be the major source of carbon for M. tuberculosis during growth on C2 substances [10]. PS catalyzes the condensation of pantothenate from D-pantoate and β-alanine for the biosynthesis of coenzyme A and acyl carrier protein in mycobacterium [11].
Metabolic engineering of Escherichia coli W3110 strain by incorporating genome-level modifications and synthetic plasmid modules to enhance L-Dopa production from glycerol
Published in Preparative Biochemistry and Biotechnology, 2018
Arunangshu Das, Neetu Tyagi, Anita Verma, Sarfaraz Akhtar, Krishna J. Mukherjee
For production of L-Dopa the strategies mentioned above and their related problems have been grossly observed and discussed by researchers. Munoz et al. reported improvement of L-Dopa production in E. coli by replacement of functional PTS system with over expression of galactose permease (GalP) and glucokinase (Glk) and deletion of transcriptional regulator tyrR which led to higher yield of aromatics. 4-hydroxyphenylacetate 3-hydroxylase (hpaBC) from E. coli, cyclohexadienyl dehydrogenase (tyrC) and chorismate mutase (pheACM) from Zymomonas mobilis were over expressed under IPTG inducible “trc” promoter. A feedback-resistant version of DAHP synthase (aroG) and tktA encoding transketolase, both from E. coli were also over expressed from a separate plasmid module. The final strains lead to a maximum titer of 1.5 g/L of L-Dopa in fermenter after 40-hr production phase.[13] Recently Wei et al. reported 8.67 g/L of L-Dopa by knocking out glucose-6-phosphate dehydrogenase gene (zwf), prephenate dehydratase and its leader peptide sequence (pheLA), transcriptional regulators (tyrosine repressor tyrR and carbon storage regulator A csrA) and switching glucose transport from the phosphotransferase system (PTS) to ATP-dependent uptake by over expression of galactose permease (galP) and glucokinase (glk). Multiplex automated genome engineering (MAGE) was used to improve L-Dopa production and the best strain after 40 hr of fed batch study yielded 8.67 g/L of L-Dopa. The fermentation medium (pH 7.0) contained 10 g/L of peptone and 5 g/L of yeast extract while the gross composition of feed was 500 g/L of glucose, 25 g/L of tryptone, 50 g/L of yeast extract, 17.2 g/L of MgSO4·7H2O, 7.5 g/L of (NH4)SO4 and 18 g/L of ascorbic acid. Thus, a highly rich composition of media had been used which itself may contains a heavy stock of tyrosine/tyrosine precursors. Thus it is subtly impossible to obtain actual L-Dopa titers converted from tyrosine synthesized by the strain from tyrosine stocks already present in Yeast Extract and Peptone. Furthermore, the study also includes over expression of hpaBC from plasmid under an inducible promoter.[14]