Why has butyrylcholinesterase been retained? Structural and functional diversification in a duplicated gene

► Evolution of BChE, in particular, subfunctionalisation of a duplicated gene. ► BChE-like activity has arisen a number of times, suggesting convergent evolution. ► Subfunctionalisation of BChE in the nervous system and in detoxification. ► Analysis of natural mutations in human BCHE in relation to BChE structure.