The 15 human tissue kallikreins (hKs) are chymotrypsin-like serine proteases, which are upregulated in several cancers. In order to develop new anticancer compounds, their structure and function should be studied. Thus, the substrate specificity of seven recombinant tissue kallikreins (hK3-7, hK10, and hK11) was determined by a positional scanning with a combinatorial peptide library. The X-ray structures of hK4, hK5, hK7, and hK10 were solved with inhibitors and complexed with metal ions. hK4 that is found in prostate and teeth crystallised as cyclic tetramers and octamers and exhibited a novel metal site between His25 and Glu77, which mediates the micromolar zinc inhibition, as confirmed by a mutational analysis. Several inhibitor complex structures of hK5 and hK7, which are both predominantly expressed in skin and inhibited by zinc, displayed zinc or copper ions bound in the substrate recognising region, explaining the respective inhibition mechanisms. Finally, hK10 possesses a deviating structure, which seems to be zymogen-like. These differences are probably based on the long 99-loop and the uncommon N-terminus with an L(16)DPE sequence. Remarkably, hK10 binds a Zn2+ with two residues of the catalytic triad (His57, Asp102, additionally Asp99). Hence, some of so-called new tissue kallikreins appear to be regulated by zinc, as well as some of the "classical" ones.      «

The 15 human tissue kallikreins (hKs) are chymotrypsin-like serine proteases, which are upregulated in several cancers. In order to develop new anticancer compounds, their structure and function should be studied. Thus, the substrate specificity of seven recombinant tissue kallikreins (hK3-7, hK10, and hK11) was determined by a positional scanning with a combinatorial peptide library. The X-ray structures of hK4, hK5, hK7, and hK10 were solved with inhibitors and complexed with metal ions. hK4 t...     »