PTER is a mammalian homolog to bacterial phosphotriesterases, enzymes that hydrolyze phosphotriester-containing organophosphate pesticides. It is expressed primarily in the proximal renal tubules and the gene has been localized in humans to chromosomal band 10p12 by in situ hybridization. PTER, in addition to FTO, MC4R, and NPC1 has recently been shown to be a new risk loci for early-onset and morbid adult obesity in European populations. At least two isoforms of PTER are known to exist.