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Arsenic
Published in Pankaj Chowdhary, Abhay Raj, Contaminants and Clean Technologies, 2020
Kiran Gupta, Alka Srivastava, Amit Kumar
Arsenic occurs in soil as inorganic and organic forms in which the inorganic forms are more prevalent. Most of the inorganic forms are found in minerals. The major part of As in soil occurs as mineral forms. However, the organic form of As is mostly present in living organisms because of the intake of As minerals. There are about 300 forms of As-enriched minerals, viz., arsenates, sulfides, sulfosalts, arsenites, arsenides, native elements, including metal alloys. The major mineral forms of As are depicted in Table 10.1. Among them, sulfide (e.g., arsenopyrite, pyrite, realgar, and loellingite) and arsenate minerals (e.g., scorodite, yukonite, and beudantite) are the mostly occurring soil-bound mineral forms (Kossoff and Hudson-Edwards, 2012), while other minerals are formed during the weathering process. When organo As compounds enter the food chain, inorganic arsenic gets converted into less-toxic organic methylated forms such as monomethyl arsine (MMA), dimethylarsine (DMA), and trimethylarsine (TMA) (Kossoff and Hudson-Edwards, 2012). Some other organic forms were also generated during World War I, suchas lewisite, cacodylic acid, and adamsite (Ellison, 2007). Other forms of organic arsenic are found in seafood, like arsenobetaine and arsenocholine (Hopenhayn, 2006).
Inorganic Chemical Pollutants
Published in William J. Rea, Kalpana D. Patel, Reversibility of Chronic Disease and Hypersensitivity, Volume 4, 2017
William J. Rea, Kalpana D. Patel
As metabolites were speciated using HPLC separation of arsenobetaine (AsB), arsenocholine (AsC), arsenate (InAsV), arsenite (InAsIII), MMA, and DMA followed by detection using ICP-MS. After subtracting AsC and AsB from the total, we calculated the percentages of InAs (InAsIII + InAsV), MMA (MMAIII + MMAV), and DMAV.
Trace Elements, Heavy Metals, and Micronutrients
Published in Epstein Eliot, The Science of Composting, 2017
In animals, arsenate and arsenite can be toxic, but natural organic arsenic compounds (e.g., arsenobetaine) are much less toxic (Anke, 1986). Only recently it has been found that As may be essential for animals (Nielsen, 1984).
The enigma of environmental organoarsenicals: Insights and implications
Published in Critical Reviews in Environmental Science and Technology, 2022
Xi-Mei Xue, Chan Xiong, Masafumi Yoshinaga, Barry Rosen, Yong-Guan Zhu
Nontoxic arsenobetaine and arsenocholine, the arsenic species primarily found in marine animals, have been considered as the end product of arsenosugar degradation (Edmonds & Francesconi, 1981). GbsB and GbsA, the enzymes encoded by the gbsAB glycine betaine synthetic operon from the rhizobacterium Bacillus subtilis, converts arsenocholine to arsenobetaine via successive oxidation reactions, where GbsB first oxidizes arsenocholine to arsenobetaine aldehyde that is subsequently oxidized to arsenobetaine by GbsA (Fig. 1D) (Hoffmann et al., 2018). In contrast, the pathway from arsenosugars to arsenocholine remains unknown. Based on arsenic species found in laboratory degradation (Foster, 2007) and feeding studies (Francesconi et al., 1989), arsenocholine has been proposed to form through the degradation of dimethylarsenoribosides (Fig. 1E), where a range of dimethylarsinoyl-hydroxycarboxylic acids (e.g. DMAA, DMAE) and the corresponding thio-arsenic compounds (e.g. thio-DMAA, thio-DMAE) are produced as intermediates. Because methylated thioarsenicals more readily interact with cysteine residues in proteins compared to the corresponding oxo arsenicals (Sun et al., 2016), thio-DMAE is considered a key precursor for arsenocholine formation, yet the formation of arsenocholine from DMAE/thio-DMAE still remains speculative. In addition, arsenobetaine has been shown to be degraded to inorganic arsenic by bacteria via the pathways [arsenobetaine→(trimethylarsine oxide)→DMAs→MAs→As(III)/As(V)] (Devesa et al., 2005). However, the pathway and molecular mechanism of arsenobetaine degradation remain to be studied.
Organoarsenical compounds: Occurrence, toxicology and biotransformation
Published in Critical Reviews in Environmental Science and Technology, 2020
Jian Chen, Luis D. Garbinski, Barry Rosen, Jun Zhang, Ping Xiang, Lena Q. Ma
Arsenobetaine (2-trimethylarsoniumylacetate and 2-(trimethylarsaniumyl) acetate) is an As-containing analog of trimethylglycine (glycine betaine). It is the major As species in almost all marine animals, accounting for >80% of total As (Maher, 1985). Arsenobetaine can also be found in non-marine organisms as diverse as mushrooms, earthworms, and terrestrial birds (Button et al., 2011). The chemical relatedness of arsenobetaine to the N-containing and environmentally-abundant glycine betaine fosters the speculations about its possible function as an osmotic stress protectant. Like other betaines, arsenobetaine can serve as an osmolyte. So arsenobetaine has both a protective function against high osmolarity and a cytoprotective role against extremes in low and high temperatures (Hoffmann et al., 2018). As arsenobetaine is widely found in marine ecosystems, human exposure to arsenobetaine is primarily through seafood consumption. Unlike arsenosugars and arsenolipids, ingested arsenobetaine in humans is excreted in urine unchanged, with little toxic effects being associated with its exposure. As the first Aso compound identified in seafoods, arsenobetaine is the most studied compound, but the details of its synthesis are still poorly understood. Its sources in the food web are unclear, though there are several theories about its biosynthetic pathway.
Arsenic removal using Chlamydomonas reinhardtii modified with the gene acr3 and enhancement of its performance by decreasing phosphate in the growing media
Published in International Journal of Phytoremediation, 2019
Angélica E. Ramírez-Rodríguez, Bernardo Bañuelos-Hernández, Mariano J. García-Soto, Dania G. Govea-Alonso, Sergio Rosales-Mendoza, M. Catalina Alfaro de la Torre, Elizabeth Monreal-Escalante, Luz M. T. Paz-Maldonado
The biotransformation of arsenic into glycerol-arsenosugar and phosphate-arsenosugar by C. reinhardtii can occur within 24 h (Miyashita et al. 2011). These arsenosugars from dead algae are likely transformed by microbial activity into arsenobetaine through the arsenocholine pathway, rendering low-toxicity organic species of arsenic (Almela et al. 2005). Moreover, Kobayashi et al. (2005) reported on the differential internalization of arsenic in wild-type strains of C. reinhardtii and arsenate-sensitive or arsenate-resistant mutants, concluding that the intracellular level of phosphate is an important factor for arsenic resistance.