Abstract
BackgroundPhylogenies of certain bioenergetic enzymes have proved to be useful tools for deducing evolutionary ancestry of bioenergetic pathways and their relationship to geochemical parameters of the environment. Our previous phylogenetic analysis of arsenite oxidase, the molybdopterin enzyme responsible for the biological oxidation of arsenite to arsenate, indicated its probable emergence prior to the Archaea/Bacteria split more than 3 billion years ago, in line with the geochemical fact that arsenite was present in biological habitats on the early Earth. Respiratory arsenate reductase (Arr), another molybdopterin enzyme involved in microbial arsenic metabolism, serves as terminal oxidase, and is thus situated at the opposite end of bioenergetic electron transfer chains as compared to arsenite oxidase. The evolutionary history of the Arr-enzyme has not been studied in detail so far.ResultsWe performed a genomic search of genes related to arrA coding for the molybdopterin subunit. The multiple alignment of the retrieved sequences served to reconstruct a neighbor-joining phylogeny of Arr and closely related enzymes. Our analysis confirmed the previously proposed proximity of Arr to the cluster of polysulfide/thiosulfate reductases but also unravels a hitherto unrecognized clade even more closely related to Arr. The obtained phylogeny strongly suggests that Arr originated after the Bacteria/Archaea divergence in the domain Bacteria, and was subsequently laterally distributed within this domain. It further more indicates that, as a result of accumulation of arsenate in the environment, an enzyme related to polysulfide reductase and not to arsenite oxidase has evolved into Arr.ConclusionThese findings are paleogeochemically rationalized by the fact that the accumulation of arsenate over arsenite required the increase in oxidation state of the environment brought about by oxygenic photosynthesis.
Highlights
Phylogenies of certain bioenergetic enzymes have proved to be useful tools for deducing evolutionary ancestry of bioenergetic pathways and their relationship to geochemical parameters of the environment
Two enzyme systems are presently known to mediate the bioenergetic use of arsenics, i.e. arsenite oxidase and respiratory arsenate reductase
A confusing multitude of acronyms denoting these two enzymes can be found in the literature, whereof Arsenite oxidase (Aro) and arsenate reductase (Arr) appear as the most sensible couple of acronyms to us
Summary
Phylogenies of certain bioenergetic enzymes have proved to be useful tools for deducing evolutionary ancestry of bioenergetic pathways and their relationship to geochemical parameters of the environment. Respiratory arsenate reductase (Arr), another molybdopterin enzyme involved in microbial arsenic metabolism, serves as terminal oxidase, and is situated at the opposite end of bioenergetic electron transfer chains as compared to arsenite oxidase. A confusing multitude of acronyms denoting these two enzymes can be found in the literature, whereof Aro (for Arsenite oxidase) and Arr (for Arsenate reductase) appear as the most sensible couple of acronyms to us. These denominations are used throughout this work. The enzyme Arr, by contrast, plays the role of a terminal oxidase in prokaryotic energy conversion (for reviews, see [5,6,7,8]) and is situated at the opposite end of bioenergetic electron transfer chains with respect to its "sisterenzyme" Aro
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
