Phosphonate inhibitors of West Nile virus NS2B/NS3 protease

West Nile virus (WNV) is a member of the flavivirus genus belonging to the Flaviviridae family. The viral serine protease NS2B/NS3 has been considered an attractive target for the development of anti-WNV agents. Although several NS2B/NS3 protease inhibitors have been described so far, most of them are reversible inhibitors. Herein, we present a series of α-aminoalkylphosphonate diphenyl esters and their peptidyl derivatives as potent inhibitors of the NS2B/NS3 protease. The most potent inhibitor identified was Cbz-Lys-Arg-(4-GuPhe)P(OPh)2 displaying Ki and k2/Ki values of 0.4 µM and 28 265 M−1s−1, respectively, with no significant inhibition of trypsin, cathepsin G, and HAT protease

The Fellowship of Privileged Scaffolds—One Structure to Inhibit Them All

Over the past few years, the application of privileged structure has emerged as a powerful approach to the discovery of new biologically active molecules. Privileged structures are molecular scaffolds with binding properties to the range of different biological targets. Moreover, privileged structures typically exhibit good drug-like properties, thus assuring more drug-like properties of modified compound. Our main objective is to discuss the privileged structures used for the development of antiviral agents

The role of capsid protease CP activity in the development of alphaviral infections

Alphaviruses belong to the worldwide distributed Togaviridae family and Alphavirus genus. They are spherical, enveloped, single-stranded RNA arthropodborne viruses. Alphaviruses are mostly transmitted by mosquitoes (Aedes spp. and Anopheles spp.) and are geographically distributed in restricted areas where appropriate vectors are present (Fig.1.). The most recognized members of this genus are Sindbis (SINV), Semliki Forest (SFV), Venezuelan equine encephalitis (VEEV), Ross River (RRV), and Chikungunya (CHIKV) viruses. Alphaviruses are infection agents for humans and many animals. Clinically, most human infections with arthritogenic alphaviruses are associated with symptoms such as fever, headache, joint pain, rash, chronic arthritis, and encephalitis. Major events during the alphaviral infection are virus entry, replication, assembly, and budding of new virions. Alphaviral RNA encodes four nonstructural and five structural proteins. Nonstructural proteins are mainly involved in the replication process and virus pathogenesis, while structural proteins form new virions. Both groups of viral proteins are produced as single polyproteins which undergo autoproteolytic maturation. This process is carried out by the two viral proteases, cysteine protease nsP4 and C protein serine protease (CP), and is considered to be critical for virus replication. The capsid protease CP is a chymotrypsin-like serine protease with the catalytic triad including His145, Asp167, and Ser219. What is important, after a suicidal autoproteolytic event the side chain of Trp267 remains bound in a hydrophobic S1 pocket thus inhibiting further trans-proteolytic activity. Alphaviral capsid protein undergoes a single proteolytic reaction before maturation and then, after selfinactivation, it assembles to form a viral capsid shell. Inhibitors of the capsid protease have significant antiviral activity. Compounds belonging to this group can be good candidates for new antiviral drugs

Substrate profiling of Finegoldia magna SufA protease, inhibitor screening and application to prevent human fibrinogen degradation and bacteria growth in vitro.

SufA, which belongs to the subtilisin-like serine protease family, contains a non-canonical Asp-His-Ser catalytic triad. Under in vitro conditions, SufA is capable of human fibrinogen hydrolysis leading to inhibition of fibrin network formation, thus suggesting its important role in the development and progression of Finegoldia magna infections. In addition, it has been demonstrated that SufA can hydrolyze antibacterial peptides such as LL-37 and the chemokine MIG/CXCL 9, hence evading host defence mechanisms. Although the SufA protease from F. magna was discovered several years ago, its optimal substrate preference has not yet been identified. Considering the role of SufA, we have focused on the profiling of its substrate sequence preference spanning S1-S3 binding pockets using the FRET (fluorescence resonance energy transfer) approach. Next, based on the structure of the P1 residue of the developed substrate, we narrowed the inhibitor screening to the phosphonic analogues of amino acids containing an arginine-like side chain. Among all the compounds tested, only Cbz-6-AmNphth(P)(OPh)2 showed any inhibitory activity against SufA displaying k2/Ki value of 10 800 M(-1) s(-1). In addition, it prevented SufA-mediated human fibrinogen hydrolysis in vitro and exhibited potent antibacterial activity against F. magna, Staphylococcus aureus and Escherichia coli. Herein, we report on the substrate specificity, synthesis and kinetic evaluation of phosphonic inhibitors of SufA protease from F. magna which could help to establish its function in pathogenesis development and may lead to the elaboration of new antibacterial drugs

Was the serine protease cathepsin G discovered by S. G. Hedin in 1903 in bovine spleen?

In the beginning of the 20th century, enzymes with proteolytic activity were classified as peptidases, Erepsin, and proteases. Among these, pepsin, trypsin, and autolytic enzymes were of the protease class. Spleen-derived proteases were poorly characterized until Sven Gustaf Hedin performed several digestion experiments with bovine spleen. He incubated minced bovine spleen under acidic or neutral conditions and characterized two active proteases; the results were published in 1903. The first protease was named α-protease and was active under neutral conditions. The second was named β-protease and was active under acidic conditions. We replicated Hedin's experiments according to his methods and found, by using activity-based probes to visualize proteases, that the historical α-protease is the present-day serine protease cathepsin G (CatG), which is known to be important in several immune processes, including antigen processing, chemotaxis, and activation of surface receptors. The β-protease, however, comprised different proteases including CatX, B, S, and D. We suggest that Hedin described CatG activity in bovine spleen over 100 years ago