Determination of isoaspartate in proteins

摘要

The invention relates to methods and means for quantitative determination of the isoaspartyl content of polypeptides via selective methylation of their fragments, catalyzed by a protein L-isoaspartyl methyltransferase enzyme. Since deamidation of asparagine side chains at specific sites of proteins and the resultant isoaspartate formation are emerging as a major contributor to protein degradation under mild conditions, the invention also concerns a method for quantitation of protein degradation associated with isoaspartate formation.