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(-NH3+)-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 degreesC 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.