Abstract
We explored the unique substrate specificity of the
primary S1 subsite of human urinary kallikrein (hK1),
which accepts both Phe or Arg synthesizing and assaying
peptides derived from PhenylacetylPheSer
ArgEDDnp, a previously described inhibitor with
analgesic and antiinflammatory activities [Emim
et al., Br. J. Pharmacol. 130 (2000), 1099 1107]. Phe
was substituted by amino acids containing larger
aliphatic or aromatic side chains as well as by nonnatural
basic amino acids, which were designed to
combine a large hydrophobic and/or aromatic group
with a positivelycharged group at their side chains.
In general, all peptides with basic amino acids represented
better inhibitors than those with hydrophobic
amino acids. Furthermore, the S1 subsite specificity
proved to be much more selective than the mere distinction
between Phe and Arg, for minor differences in
the side chains of the nonnatural amino acids resulted
in major differences in the Ki values. Finally, we
present a series of peptides that were assayed as
competitive inhibitors for human tissue kallikrein that
may lead to the development of novel peptides, which
are both more potent and selective.
