A single residue influences the reaction mechanism of ammonia lyases and mutases.

All ways lead to Rome? Computer modeling and kinetic measurements identified a distinct residue in Phe/Tyr ammonia lyases (PAL/TAL) which controls whether the Friedel-Crafts or an E(1)cB reaction mechanism takes place. Hence, Glu484 in pcPAL favors the Friedel-Crafts reaction (see picture, MIO = 4-methylidene imidazol-5-one) whereas an Asn in TAL gives an elimination reaction. These mechanistic investigations also reveal activity of a PAL mutant and a TAL towards an amino alcohol.