Predicting the protein family of methyl parathion hydrolase

Six motifs of Methyl Parathion Hydrolase (MPH) were discovered using a method based on the Hidden Markov Model (HMM). Most MPH from TrEMBL (Release 48.6) could be recognised by these six motifs. When these six motifs were projected onto the 3D enzyme structure, we discovered that all of them closely surrounded the active centre and might play an important role in structure and function of the enzyme. By comparing the motifs of MPH with PH and analysing the phylogenetic tree, we found that these two enzymes, with substrates differing from only two methyl groups, belonged to two different protein families. The MPH belonged to the Lactamase family, and the PH belonged to the Phosphotriesterase (PTE) family.