Engineering Proteases for Mass Spectrometry-Based Post Translational Modification Analyses.

Protein post-translational modifications (PTMs) are important modulators of virtually all cellular processes, and frequently correlate with not only the rate but also severity of diseases. There has been considerable interest to map all possible PTM sites to be used as drug targets. Current approaches for PTM analysis suffer from a number of challenges; one of which is the lack of a PTM specific cleaving reagent. A central technology for global quantitative PTM analysis, mass spectrometry (MS) based proteomics, is biased toward trypsin due to its high activity and specificity. This bias becomes a problem when a PTM is located at or near tryptic cleavage sites, in which case the PTM might block recognition by trypsin, resulting in missed cleavage and sequence coverage gaps. Reviewed here are recent advances in engineering new proteases for PTM analyses, and how these new proteases are beginning to address current challenges in the field.