Recently, it has been reported that some metal complexes can act as artificial proteases. In particular, the Lewis acid scandium(III) triflate has been shown to catalyze the cleavage of peptide bonds N- and C-terminal to serine and threonine residues. Therefore, we investigated if this compound can also be used for the cleavage of proteins. For this purpose, several single proteins, the 20S immune-proteasome (17 proteins), and the Universal Proteomics Standard UPS1 (48 proteins) were analyzed by MALDI-MS and/or LC-MS. A high cleavage specificity N-terminal to serine and threonine residues was observed.