FBXO31 is a substrate adapter for the SCF-type ubiquitin ligase complex SCF/FBXO31 which ubiquitylates C-terminal amide-bearing proteins (CTAPs), thereby triggering their proteasomal degradation in human cells. CTAPs can arise from internal protein cleavage events during which the N-terminal fragment is left with an amidated C-terminus (-0.984016 Da). We searched for such cleavage events (semi-enzymatic C-terminus and C-terminal amidation) in previously published datasets and in own experimental data. These include: - Re-analysis of tissue samples from a deep human proteome atlas (PXD010154) - IP-MS of AARS1, a client of the CTAP reader FBXO31 (MFM-X208) - In vitro fragmentation of purified hemoglobin (MFM-X294, MFM-X298) and tRNA ligase complex (MFM-X314) Experiments are labeled with experiment IDs (MFM-X...). PSM tables contain Experiment IDs and interpretable sample aliases.