Arsenic can be found world-wide in drinking water. Humans and other organisms have well studied mechanisms to eliminate arsenic taken into the body from drinking water or other sources. Traditionally arsenic methylation has been considered part of the elimination process.
In the 2006 JBC paper “Human arsenic methyltransferase (AS3MT) pharmacogenetics: gene resequencing and functional genomics studies.” by
Wood TC, Salavagionne OE, Mukherjee B, Wang L, Klumpp AF, Thomae BA, Eckloff BW, Schaid DJ, Wieben ED, Weinshilboum RM.
We discussed a variant with 350% of the enzymatic activity compared to the wild-type protein, and a series of genetic variations in the 5′ UTR of the methyltrsnsferase gene.
So, how could an enzyme with improved activity be bad?
And, why would mutations in a part of the untranslated region of an mRNA effect the methyltransferase activity?