We present the data and the technology, a combination of which allows us to determine the identity of
proprotein convertases (PCs) related to the processing of specific
protein targets including viral and bacterial pathogens. Our results, which support and extend the data of other laboratories, are required for the design of effective inhibitors of PCs because, in general, an inhibitor design starts with a specific substrate. Seven
proteinases of the human PC family cleave the multibasic motifs R-X-(R/K/X)-R downward arrow and, as a result, transform proproteins, including those from pathogens, into biologically active
proteins and
peptides. The precise cleavage preferences of PCs have not been known in sufficient detail; hence we were unable to determine the relative importance of the individual PCs in
infectious diseases, thus making the design of specific inhibitors exceedingly difficult. To determine the cleavage preferences of PCs in more detail, we evaluated the relative efficiency of
furin, PC2, PC4,
PC5/6, PC7, and PACE4 in cleaving over 100 decapeptide sequences representing the R-X-(R/K/X)-R downward arrow motifs of human, bacterial, and
viral proteins. Our computer analysis of the data and the follow-on cleavage analysis of the selected full-length
proteins corroborated our initial results thus allowing us to determine the cleavage preferences of the PCs and to suggest which PCs are promising drug targets in
infectious diseases. Our results also suggest that pathogens, including
anthrax PA83 and the
avian influenza A H5N1 (bird flu)
hemagglutinin precursor, evolved to be as sensitive to PC proteolysis as the most sensitive normal human
proteins.