Single residues dictate the co-evolution of dual esterases: MCP hydrolases from the α/β hydrolase family.

Several members of the C-C MCP ( meta -cleavage product) hydrolase family demonstrate an unusual ability to hydrolyse esters as well as the MCPs (including those from mono- and bi-cyclic aromatics). Although the molecular mechanisms responsible for such substrate promiscuity are starting to emerge, the full understanding of these complex enzymes is far from complete. In the present paper, we describe six distinct α/β hydrolases identified through genomic approaches, four of which demonstrate the unprecedented characteristic of activity towards a broad spectrum of substrates, including p -nitrophenyl, halogenated, fatty acyl, aryl, glycerol, cinnamoyl and carbohydrate esters, lactones, 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate and 2-hydroxy-6-oxohepta-2,4-dienoate. Using structural analysis and site-directed mutagenesis we have identified the three residues (Ser 32 , Val 130 and Trp 144 ) that determine the unusual substrate specificity of one of these proteins, CCSP0084. The results may open up new research avenues into comparative catalytic models, structural and mechanistic studies, and biotechnological applications of MCP hydrolases.