The present invention relates to enzymes capable of hydrolysing organophosphate (OP) molecules. In particular, the invention relates to variants of the OpdA enzyme from Agrobacterium that display improved activity when compared to the naturally occurring OpdA. The invention is also towards polypeptides that have organophosphate hydrolysing activity for the organophosphates chlorpyrifos methyl, diazinon and parathion ethyl.