Improved conditions for the removal of 2-oxoacyl groups from the N-terminus of proteins

Proteins with R–CO–CO–NH– at the N-terminus, rather than the usual R–CH(– NH 3 + )–CO–NH–, are produced by non-enzymic transamination and also occur in the pyruvoyl enzymes. The oxoacyl group may be specifically removed from a model peptide, in yields of 70–80%, by treating them in 0.1 M phosphate buffer at 37°C for 24 h with 25 mM of the N -phosphonomethyl derivative of phenylene-1,2-diamine. This provides mild conditions for the stepwise removal of N-terminal residues without denaturation.