Abstract: The present invention provides a novel method for stabilizing proteins, by first identifying the proteolytic sites using N- or C-terminal technology, followed by modification of said sites in order to create stabilized proteins, no longer subject to proteolytic cleavage. the method of the invention immediately provides the user with the exact amino acid position of the proteolytic cleavage site in the protein(s) of interest, even in a complex protein sample. This makes the specific modification of such a site much easier and increases the expectation of success as compared to the amount of effort needed, even in a complex protein sample.