Crystallization and preliminary X-ray crystallographic studies of the ArsI C–As lyase fromThermomonospora curvata

Arsenic is a ubiquitous and carcinogenic environmental element that enters the biosphere primarily from geochemical sources, but also through anthropogenic activities. Microorganisms play an important role in the arsenic biogeochemical cycle by biotransformation of inorganic arsenic into organic arsenicals andvice versa. ArsI is a microbial nonheme ferrous-dependent dioxygenase that transforms toxic methylarsonous acid to the less toxic inorganic arsenite by C–As bond cleavage. An ArsI ortholog from the thermophilic bacteriumThermomonospora curvatawas expressed, purified and crystallized. The crystals diffracted to 1.46 Å resolution and belonged to space groupP43212 or its enantiomerP41212, with unit-cell parametersa=b= 42.2,c= 118.5 Å.

Methanogenic Inhibition by Arsenic Compounds

ABSTRACT The acute acetoclastic methanogenic inhibition of several inorganic and organic arsenicals was assayed. Trivalent species, i.e., methylarsonous acid and arsenite, were highly inhibitory, with 50% inhibitory concentrations of 9.1 and 15.0 μM, respectively, whereas pentavalent species were generally nontoxic. The nitrophenylarsonate derivate, roxarsone, displayed moderate toxicity.