Inhibitor cysteine knots (ICK) also known as "knottins," are cysteine-rich peptides typically composed of approximately 30 amino acids. These peptides exhibit a characteristic robust structure featuring three antiparallel β-sheets that are "knotted" together by three disulfide bonds. This structural motif confers stability to the protein, rendering it resistant to thermal denaturation and proteolysis. Consequently, inhibitor cysteine knots hold great promise as scaffolds for developing new peptide drugs. In this study, we present the synthesis and evaluation of six potential inhibitors targeting KLK13, utilizing the Ecballium elaterium trypsin II inhibitor (EETI-II) as the leading structure. The peptides were synthesized in solid-phase peptide synthesis with an automated peptide synthesizer. Subsequently, they were oxidized using iodine and then quenched with an anion exchange resin. Both linear and oxidized compounds were obtained and subjected to kinetic studies. The inhibitory activity against KLK13 was observed exclusively in the oxidized analogues of the synthesized compounds. Linear peptides exhibited lower affinity towards KLK13, highlighting the critical role of the disulfide bridge in the structure of the EETI-II analogues for inhibiting the enzyme activity.
The discovery of quantum dots (QDs) was a breakthrough event as it influenced almost every area of our lives. They are used in new technologies, the food industry, clothing production, and finally in medicine. Due to their unique properties, QDs are successfully used in the diagnosis of diseases of various origins - the so-called civilization diseases, infections and cancers. Quantum dots can also serve as tools to monitor the proteolytic activity of enzymes, effectively lowering the detection limit. Our team has been dealing with the proteolytic activity of enzymes for many years, especially in disease diagnosis, for which we also use quantum dots. In this article, we presented the main trends in the use of QDs as diagnostic tools.
Proteolytic enzymes are essential for the proper functioning of every living cell. Due to their great importance in controlling metabolic changes in living organisms, they could be used in the diagnosis of civilization diseases. Hence, the search for new methods of determining and controlling their activity is extremely important. Our team, has been studying substrates of proteases and their potential use in detection of biomarkers activity for many years.
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