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Cyanobacterial toxins
Published in Ingrid Chorus, Martin Welker, Toxic Cyanobacteria in Water, 2021
The biosynthesis of the ATXs involves a polyketide synthase (PKS) family of multifunctional enzymes with a modular structural organisation as described in Méjean et al. (2014). A detailed biochemical description of the adenylation domain protein AnaC revealed the activation of proline as starter, and not glutamate as previously proposed (Dittmann et al., 2013). The biosynthetic pathway describes AnaB, AnaC and AnaD as acting in the first steps (which have been fully reproduced in vitro; Méjean et al., 2009; Méjean et al., 2010; Mann et al., 2011), and AnaE, AnaF, Ana J and AnaG catalysing the following steps, with the latter adding two carbons and methylating the substrate to produce HTX. The release of ATXs may be catalysed by the thioesterase AnaA, although this has not been experimentally verified (Pearson et al., 2016) or a spontaneous decarboxylation step may occur to yield the amine alkaloid ATX (Dittmann et al., 2013).
Transformation of Natural Products by Marine-Derived Microorganisms
Published in Se-Kwon Kim, Marine Biochemistry, 2023
Thayane Melo de Queiroz, André Luiz Meleiro Porto
Polyketides are a class of natural products normally formed from the condensation of methylmalonyl-CoA, propanoyl-CoA and acetyl-CoA units by the action of polyketide synthase (PKS) enzymes. These compounds are found in plants, fungi, and bacteria (Hertweck, 2009; Dewick, 2009). The polyketides have relevant biological properties and are used as antibiotics, cholesterol reducers, antifungals, anti-tuberculosis agents, and antineoplastics (Dewick, 2009; Goswami et al., 2012; Lim et al., 2013; Jelić and Antolović, 2016).
Properties, toxicity and current applications of the biolarvicide spinosad
Published in Journal of Toxicology and Environmental Health, Part B, 2020
Vanessa Santana Vieira Santos, Boscolli Barbosa Pereira
Analysis of DNA sequencing and target gene disruptions revealed the spinosyn biosynthesis pathway is encoded by 27 genes in a 74-kb region of the Saccharopolyspora spinosa genome, which are involved in the synthesis, modification, and attachment of the deoxysugars and in the modification of the macrolactone (Waldron et al. 2000). Specifically, five large genes (spn A, B, C, D, and E) are encoding a type I polyketide synthase (PKS) and four genes (spnF, spnJ, spnL, spnM) are responsible to convert the product of PKS. The genes spnG, spnH, spnI, and spnK are related to the rhamnose attachment and methylation; spnP, spnO, spnN, spnQ, spnR, and spnS, are involved in forosamine biosynthesis; and four genes (ORFL15, ORF-L16, ORF-R1, and ORF-R2) exerted no marked effect on spinosad biosynthesis (Xue et al. 2013).
Response of microcystin biosynthesis and its biosynthesis gene cluster transcription in Microcystis aeruginosa on electrochemical oxidation
Published in Environmental Technology, 2019
Yu Gao, Kazuya Shimizu, Chie Amano, Xin Wang, Thanh Luu Pham, Norio Sugiura, Motoo Utsumi
Biochemical and genetic studies have suggested that mixed polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) is responsible for the production of MCs [13]. Tillett et al. [14] identified and sequenced the gene cluster mcy operon, which encodes the MC synthetase gene cluster in M. aeruginosa PCC7086. This 55-kb sequence consists of 10 open reading frames bidirectionally transcribed from a central 732-bp intergenic region between mcyA and mcyD. The description of the mcy operon facilitates new experimental approaches to study the production of MCs. Several studies have demonstrated the up-regulation of mcy transcript levels under high light intensity or in the presence of anthracene [15–17]. Sevilla et al. [18] pointed that iron deficiency slightly affected mcyD transcription, which was correlated with an increase in MC-LR levels in the cells. Transcriptional analysis is apparently a good tool for understanding physiological responses. Real-time reverse transcription polymerase chain reaction (RT-qPCR) matches the evident requirement for quantitative data analysis in various fields and is the method of choice for quantifying mRNA [19,20]. RT-qPCR has been used to analyse the relationship between the transcription level of mcy genes and environmental factors [21–23].
Effects of glycerol and glucose on docosahexaenoic acid synthesis in Aurantiochyrium limacinum SFD-1502 by transcriptome analysis
Published in Preparative Biochemistry & Biotechnology, 2023
Huaqiu Zhang, Xiangying Zhao, Chen Zhao, Jiaxiang Zhang, Yang Liu, Mingjing Yao, Jianjun Liu
At present, fatty acid synthase (FAS) pathway and polyketide synthase (PKS) pathway are considered as two key pathways of DHA biosynthesis in Aurantiochytrium.[24–27] Because these two pathways seem to lack complete genes for DHA synthesis alone, the relative contribution of these two pathways to DHA synthesis is unclear, and it is speculated that DHA may be produced through the combined action of FAS and PKS system.[24] The FAS pathway is subsequently modified by several elongases and desaturase enzymes with the participation of oxygen.[26] The PKS pathway involves a series of dehydration, reduction and condensation reactions, but does not require the participation of oxygen.