Q:

How do the toxicities of arsenate and arsenite compare?

So I was browsing the detoxification metabolistic mechanisms for E. coli, and came across an arsenic detoxification mechanism that converted arsenate to arsenite using a glutaredoxin. So my question is, how does the toxicity of arsenate compare to arsenite? And what is the use of this pathway in E. coli?

A:

I see now. 
According to the same website with the reaction mechanism, 

Although the arsenite formed is more toxic than arsenate , it can be extruded from some bacteria by EC 3.6.3.16 , arsenite-transporting ATPase; in other organisms, arsenite can be methylated by EC 2.1.1.137 , arsenite methyltransferase, in a pathway that produces non-toxic organoarsenical compounds. cf EC 1.20.4.4, arsenate reductase (thioredoxin) .

