More level 1 tissue-specific proteoforms were identified in a Subsequence search (previously called BioMarker search that identifies portions of full length proteoforms ) than in Absolute Mass searches. Specifically, 2,548 proteoforms were identified in Subsequence searching compared to 295 proteoforms identified in Absolute Mass searches. Subsequence searches identify proteolytic fragments that often arise from endogenous proteolytic events and can serve as significant biomarkers. While a portion of these proteoforms may be the product of non-specific proteolysis, the consensus sequence of cleavage sites varied across tissues (Figure ). Truncated proteoforms from the heart, kidney, and small intestine showed enrichment of F, Y, W, and L at P1, which suggests chymotrypsin activity. Spleen proteoforms demonstrated enrichment of hydrophobic residues but no apparent sequence specificity. This lack of specificity combined with a high proteoform to protein ratio agrees well with the role of the spleen for scavenging senescent blood cells. Lung proteoforms had a higher propensity of cysteine at P1, which is not commonly observed for specific proteases. This enrichment was driven by 24 of the 715 lung-specific proteoforms with N-terminal cleavage. Nine of these 24 proteoforms originate from collapsing response mediator protein 2 (CRMP-2, Q16555), with cleavage occurring at C439 (Figure ).