Complex Inhibitory Mechanism of Glycomimetics with Heparanase.

Heparanase (HPSE) is the only mammalian endo-ß-glucuronidase known to catalyze the degradation of heparan sulfate. Dysfunction of HPSE activity has been linked to several disease states, resulting in HPSE becoming the target of numerous therapeutic programs, yet no drug has passed clinical trials to date. Pentosan polysulfate sodium (PPS) is a heterogeneous, FDA-approved drug for the treatment of interstitial cystitis and a known HPSE inhibitor. However, due to its heterogeneity, characterization of its mechanism of HPSE inhibition is challenging. Here, we show that inhibition of HPSE by PPS is complex, involving multiple overlapping binding events, each influenced by factors such as oligosaccharide length and inhibitor-induced changes in the protein secondary structure. The present work advances our molecular understanding of the inhibition of HPSE and will aid in the development of therapeutics for the treatment of a broad range of pathologies associated with enzyme dysfunction, including cancer, inflammatory disease, and viral infections.

Computational design and experimental characterisation of a stable human heparanase variant.

Heparanase is the only human enzyme known to hydrolyse heparin sulfate and is involved in many important physiological processes. However, it is also unregulated in many disease states, such as cancer, diabetes and Covid-19. It is thus an important drug target, yet the heterologous production of heparanase is challenging and only possible in mammalian or insect expression systems, which limits the ability of many laboratories to study it. Here we describe the computational redesign of heparanase to allow high yield expression in Escherchia coli. This mutated form of heparanase exhibits essentially identical kinetics, inhibition, structure and protein dynamics to the wild type protein, despite the presence of 26 mutations. This variant will facilitate wider study of this important enzyme and contributes to a growing body of literature that shows evolutionarily conserved and functionally neutral mutations can have significant effects on protein folding and expression.

Challenges of short substrate analogues as SARS-CoV-2 main protease inhibitors.

Specific anti-coronaviral drugs complementing available vaccines are urgently needed to fight the COVID-19 pandemic. Given its high conservation across the betacoronavirus genus and dissimilarity to human proteases, the SARS-CoV-2 main protease (Mpro) is an attractive drug target. SARS-CoV-2 Mpro inhibitors have been developed at unprecedented speed, most of them being substrate-derived peptidomimetics with cysteine-modifying warheads. In this study, Mpro has proven resistant towards the identification of high-affinity short substrate-derived peptides and peptidomimetics without warheads. 20 cyclic and linear substrate analogues bearing natural and unnatural residues, which were predicted by computational modelling to bind with high affinity and designed to establish structure-activity relationships, displayed no inhibitory activity at concentrations as high as 100 µM. Only a long linear peptide covering residues P6 to P5' displayed moderate inhibition (Ki = 57 µM). Our detailed findings will inform current and future drug discovery campaigns targeting Mpro.