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The Structure of Pyruvate Carboxylase
Published in D. B. Keech, J. C. Wallace, Pyruvate Carboxylase, 2018
John C. Wallace, Simon B. Easterbrook-Smith
Although very little of the sequence of pyruvate carboxylase is known, there is, among the 19-residue sequence flanking the biotin attachment site,712 a sequence of five amino acids from which may be inferred a 14-base cDNA sequence complementary to the biotin carboxylase mRNA and containing only two possible mismatches. Thus, From the nucleotide sequences of chicken α683 and β-682 globins and histones H2A and H2B,380 it would seem that in this species, AAG and GAG are the mRNA codons favored for lysine and glutamate, respectively.
Microbial Pathways of Lipid A Biosynthesis
Published in Helmut Brade, Steven M. Opal, Stefanie N. Vogel, David C. Morrison, Endotoxin in Health and Disease, 2020
Paul D. Rick, Christian R. H. Raetz
A functional waaM gene product is essential for cell viability above 32°C, and it appears that WaaM is somehow involved in coupling phospholipid synthesis, LPS synthesis, and growth rate. Accordingly, the LPS molecules of cells possessing an insertionally inactivated waaM gene are depleted in both laurate and myristate at both 30 and 42°C (121). However, such mutants lose viability when grown in rich media at temperatures greater than 33°C, and cell death is accompanied by filamentation and bulging at potential septa sites or at the ends of the cell (116,118). In contrast, WaaM appears to be dispensible at slow growth rates regardless of the temperature. Thus, when cells possessing an insertionally inactivated waaM gene are grown at 42°C in defined media containing a poor carbon source, generation times of greater than 70 minutes result without attendant morphological aberrations or a loss in viability (116,118). When waaM null mutants are shifted from permissive conditions (33°C, rich media) to nonpermissive conditions (42°C, rich media), they continue to grow at the same rate, but they synthesize phospholipids at the rate required for growth at 42°C, resulting in a greatly increased phospholipid:protein ratio (121). Spontaneous extragenic suppressor mutations have been isolated in accA and accB genes, which allow waaM null mutants to grow at elevated temperature in rich media (121); these genes encode the biotin carboxyl carrier protein and biotin carboxylase subunits of acetyl coenzyeme A carboxylase complex, respectively. The mutations in accA and accB result in a decreased rate of phospholipid synthesis, which apparently restores the balance between phospholipid synthesis and growth rate at elevated temperature in rich media.
Biodiesel Production from Microalgal Biomass
Published in Gokare A. Ravishankar, Ranga Rao Ambati, Handbook of Algal Technologies and Phytochemicals, 2019
Srijoni Banerjee, Debabrata Das
Metabolic engineering deals with regulating or turning the metabolic pathway inside the cell to trigger the target metabolite production. Different strategies like flux balance analysis, engineering different enzymes towards lipid biogenesis, carbon partitioning, overexpression of gene, transcription factor engineering and proteomics approaches (Banerjee et al. 2016) can be adopted for triggering the target metabolite. Genetic manipulation in microalgae is challenging as editing tools are species specific and cannot be used interchangeably because of codon usage, defensive strategies, uptake of nucleic acid and porosity of cell (Banerjee et al. 2016). Microalgae metabolic engineering figured the origin of fourth-generation biodiesel production with an aim of transgenic microalgae development (Lu et al. 2011). Until today lipid metabolism with a detailed description of biosynthetic pathways that modify the chain length or saturation/unsaturation of fatty acids has not been meticulously examined for microalgae. However, scientists reported that many genes responsible for the lipid metabolism in higher plants have also found to be homologous with the microalgal genome sequences (Radakovits et al. 2010). Research attempts were made several times to up-regulate the ACCase enzyme in lipid metabolism pathway to induce or maximize lipid production but the success story is still awaited. In the model organism Chlamydomonas reinhardtii the endogenous gene source of the fatty acid-acyl carrier protein thioesterases enzyme was modified to produce shorter chain length fatty acids (Blatti et al. 2012). CRISPRi (clustered regularly interspaced short palindromic repeats interference) was used for the first time to regulate expression of exogenously supplied rfp gene as a proof-of-concept and endogenous PEPC1 gene as a proof-of-function in Chlamydomonas reinhardtii to enhance the lipid production (Kao and Ng 2017). 13C metabolic flux analysis of Chlamydomonas reinhardtii revealed that Acetyl-coA which was synthesized in plastid during lipid metabolism is directly incorporated in fatty acid synthesis (Boyle et al. 2017). Proteomics study of Neochloris oleoabundans under nitrogen limited condition revealed that acyl carrier protein and protein biotin carboxylase is up-regulated under nitrogen deprived conditions (Morales-Sánchez et al. 2016).
Mechanism of biotin carboxylase inhibition by ethyl 4-[[2-chloro-5-(phenylcarbamoyl)phenyl]sulphonylamino]benzoate
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Matthew K. Craft, Grover L. Waldrop
Acetyl-CoA carboxylase (ACC) is the multi-subunit complex that catalyses the first committed step in fatty acid synthesis22. The complex catalyses the two half reactions, shown in Scheme 1. In the first half reaction, biotin carboxylase (BC) catalyses the ATP dependent carboxylation of the vitamin biotin, which is covalently attached to biotin carboxyl carrier protein (BCCP). This forms a carboxybiotin intermediate. In the second half reaction, carboxyltransferase (CT) transfers the carboxyl group from the carboxybiotin intermediate onto acetyl-CoA, forming malonyl-CoA. The BC and CT subunits retain their activity when isolated separately and can utilise free biotin as a substrate22,23.
Responses to iron oxide and zinc oxide nanoparticles in echinoderm embryos and microalgae: uptake, growth, morphology, and transcriptomic analysis
Published in Nanotoxicology, 2020
Anne-Marie Genevière, Evelyne Derelle, Marie-Line Escande, Nigel Grimsley, Christophe Klopp, Christine Ménager, Aude Michel, Hervé Moreau
Among the highly up-regulated contigs responding to ZnO ENPs, 17 were related to the enriched BP-transcription regulation GO terms. Several of these genes belong to the signaling pathways that specify cell fate along the sea urchin developmental axes such as FoxQ2, Admp1 and 2, Unc4 or Lefty (Figure S4). Other components of the gene regulatory networks (GRNs) which control development patterning, although not classified under this GO group, were highly down-regulated, including genes such as ankAT-1, dkk3 or sfrp5. Moreover, in agreement with the complete inhibition of spicule growth when embryos were challenged with ZnO ENPs, the expression of the spicule matrix gene SM30 was found to be repressed in response to ZnO ENPs and ZnSO4. This inhibition was confirmed by qPCR (data not shown). The BP-GO “transmembrane transport” type of functions were also enriched. These included predicted Zn transporters of the ZIP family, ZIP 10 and 12, ZIP12 being more highly down-regulated by ZnO ENPs and Zn2+ while up-regulated by Fe2O3 ENPs, as mentioned above and not affected by Fe3+. In addition, MF-GO terms related to “Acetyl-CoA or biotin carboxylase activities” were also enriched among the highly down-regulated contigs. A KEGG analysis of these contigs showed that the encoded ACAC.1.3, 2.3, and 3.3 proteins belong to the AMPK signaling pathway which affects fatty acid biosynthesis. The enriched cholinesterase activity GO term includes the Cholinesterase 1 and 2 encoding contigs, the second one being highly down-regulated. Many of the contigs that were highly regulated in response to ZnO ENPs were also highly affected after exposure to ZnSO4, however our analysis also revealed DE contigs specifically responding to ZnO ENPs but not to ZnSO4 (Figure 4). Twenty-nine contigs in the latter group were highly stimulated, including a multidrug and toxin extrusion protein (Sina_LOC100891823) and a tubulin alpha-1 chain (TBA1.1.12), while 53 genes were highly repressed, most of them encoding uncharacterized proteins.