Peptide splicing in a double-sequence analogue of trypsin inhibitor SFTI-1 substituted in the P₁ positions by peptoid monomers.

Recently, we described a process of trypsin-assisted peptide splicing of analogs of trypsin inhibitor SFTI-1, that seems to be very similar to proteasome-catalyzed peptide splicing. Here, we show, for the first time, that a peptide-peptoid hybrid (peptomer) can also be spliced by trypsin. Incubation of a double sequence SFTI-1 analog, containing two peptoid monomers, with equimolar amount of trypsin leads to formation of monocyclic peptomer as the main product. We proved that the peptide bond formed by a peptoid monomer is not only digested by trypsin but also participates in the enzyme-assisted splicing process.