Selection of an Amino Acid Site with One of the Fastest Cleavage Kinetics by the Endosomal Protease Cathepsin B for Potential Use in Drug Delivery Systems.

ABSTRACT

On the basis of known published data, six peptide sequences were selected that are potentially capable of being rapidly cleaved by the endosomal protease cathepsin B. For comparison, the cleavage of common linker sequences, polyglycine and polyglycine-serine, by cathepsin B was also studied. Different ends of these peptides were labeled with sulfoCyanine3 and sulfoCyanine5 fluorescent dyes, between which Förster resonant energy transfer (FRET) is possible. The kinetics of cleavage of peptides by cathepsin B was studied on a multimodal plate reader by FRET signal reduction. FKFL and FRRG cleavage sites have been shown to be the most suitable for potential use in various drug delivery systems. These sites are much more efficiently cleaved under slightly acidic conditions of endosomes than at neutral extracellular pH.