Respiratory arsenate reductases

Krafft T, JM Macey (1998) Purification and characterization of the respiratory arsenate reductase of Chrysio-genes arsenatis. Eur J Biochem 255 647-653. 

Saltikov CW, DK Newman (2003) Genetic identification of a respiratory arsenate reductase. Proc Natl Acad Sci USA 100 10983-10988. 

Chrysiogenes arsenatis is the only known organism capable of using acetate as the electron donor and arsenate as the terminal electron acceptor for growth. This reduction of arsenate to arsenite is catalyzed by an inducible respiratory arsenate reductase, which has been isolated and characterized by Kraft and Macy (1998). Arsenate reductase (Arr) from C. arsenatis is a... 

Recently, the respiratory arsenate reductase was characterized from Shewanella sp. strain ANA-3 (Malasam et al, 2008), which was initially identified in the same strain... 

FIGURE 72.2. Arsenic detoxification mechanisms (reduction, oxidation, methylation, and resistance) in prokaryotes. (A) Respiratory arsenate reductase (Arr) is involved in the reduction of As(V) by the dissimilatory arsenate respiring organisms. (B) Arsenite oxidase (Aox/Aso) is responsible for oxidation of As(III) by chemoautotrophic or heterotrophic arsenite oxidizers. 

Alcaligenes faecalis and five members of the p Proteobacteria are heterotrophic arsenite oxidizers, whereas Pseudomonas arsenitoxidans and NT-26 grew anaerobically through chemoautotrophic oxidation (Oremland and Stolz, 2005 Santini et al, 2000). However, six members of a Proteobacteria (Ben-5, NT-3, NT-4, NT-2, NT-26, and NT-25) and one member of y Proteobacteria (MLHE-1) were known chemohthoautotrophic arsenite oxidizers (Oremland et al, 2002). The best characterized and probably most studied of aU arsenite oxidizers is Alcaligenes faecalis, a heterotrophic arsenite oxidizer (Osborne and Enrlich, 1976). The arsenite oxidase from Alcaligenes faecalis has been purified and structurally characterized (Ellis et al, 2001). A similar enzyme has also been purified from the heterotrophic arsenite oxidizers Hydrogenophaga sp. strain NT-14 (Vanden Hoven and Santini, 2004) and the chemolithoautotrophic Rhizobium sp. strain NT-26 (Santini and Vanden Hoven, 2004), which indicate that the arsenite oxidase enzyme is also a member of the DMSO reductase family of molybdenum enzymes, similar to the respiratory arsenate reductases (Arr). The arsenite oxidase heterodimer comprises an 88 kDa catalytic subunit encoded by the aoxB gene that contains a [3Fe-4S] cluster and molybdenum bound to the pyranopterin cofactor and a 14 kDa subunit... 

Afkar, E., Lisak, J., Saltikov, C., Basu, P., Oremland, R.S., Stolz, J.F. (2003). The respiratory arsenate reductase from Bacillus selenitireducens strain MLSIO. FEMS Microbiol Lett. 226 107-12. 

Preliminary biochemical studies of the enzyme that catalyzes arsenate reduction in Sulfurospirillum barnesii have been conducted and the information only cited in two review articles (12,13). This enzyme is an integral membrane protein with a calculated mass of 100 kDa consisting of three different subunits 65, 31, and 22 kDa. The equivalent enzyme from Desulfomicrobium sp. str. Ben-RB (9) is discussed in Section III.D. The only respiratory arsenate reductase that has been studied in detail is that of C. arsenatis (14), discussed in Section II.D. 

This chapter concentrates on arsenate respiration by Chrysiogenes arsenatis and Desulfomicrobium sp. str. Ben-RB. The evidence indicates that they have specific respiratory arsenate reductases involved in energy generation. The isolation, phytogeny, physiology, and biochemistry of arsenate reduction are described separately for each organism. 

The recently isolated Desulfotomaculum strain Ben-RB is able to grow using lactate as a substrate and arsenate as the sole electron acceptor (Macy et al. 2000). It has been proposed that arsenate reductase is associated with the respiratory chain of this organism, because >98% of the arsenate reductase bound to the plasma membrane. 

Figure 1 Bacterial reduction of arsenate and oxidation of arsenite. (A). Cytoplasmic arsenate reductase (ArsC) as encoded by bacterial ars operons along with chromosomaUy encoded Pit and Pst phosphate transport systems with arsenate as an alternative substrate. After reduction from arsenate to arsenite, arsenite is removed from the cell by the ArsB membrane protein. (B). Anaerobic periplasmic arsenate reductase. (C). Aerobic periplas-mic arsenite oxidase, hnked via azurin to the respiratory chain.

Perez-Jimenez, J.R., DeFraia, C., Young, L.Y. (2005). Arsenate respiratory reductase gene (arrA) for Desulfosporosinus sp. strain Y5. Biochem. Biophys. Res. Commun. 338 825-9. 

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