Based on our description of a new family of fungal peptidase inhibitors, Cocaprins, a new Merops family I106 was established. Members of our department Jerica Saboti\u010d, Tanja Zupan, Milica Peri\u0161i\u0107 Nanut and Janko Kos worked on the biochemical characterization in collaboration with Miha Renko and Du\u0161an Turk from the Department of Biochemistry and Molecular Biology, who performed the structural characterization, and with Markus K\u00fcnzler, David F. Plaza and Stefanie S. Schmieder from ETH Z\u00fcrich, who analyzed the gene family and its expression during fruiting body development in Coprinopsis cinerea. The Cocaprins exhibit a completely new arrangement of inhibitory functions, and their cysteine peptidase inhibitory profile and inhibitory site differ from those of mycocypins of families I48 and I85, which we described previously. The inhibitory site for aspartic peptidases is located at a different site than that for cysteine peptidases. This new family of inhibitors of peptidases with a beta-trefoil fold extends the incredible versatility of loop functionalization of this fold, making it an ideal scaffold for designer peptidase inhibitors.<\/p>\n\n\n\n