4-O-Substituted Glucuronic Cyclophellitols are Selective Mechanism-Based Heparanase Inhibitors

Degradation of the extracellular matrix (ECM) supports tissue integrity and homeostasis, but is also a key factor in cancer metastasis. Heparanase (HPSE) is a mammalian ECM-remodeling enzyme with β-D-endo-glucuronidase activity overexpressed in several malignancies, and is thought to facilitate tumor growth and metastasis. By this virtue, HPSE is considered an attractive target for the development of cancer therapies, yet to date no HPSE inhibitors have progressed to the clinic. Here we report on the discovery of glucurono-configured cyclitol derivatives featuring simple substituents at the 4-O-position as irreversible HPSE inhibitors. We show that these compounds, unlike glucurono-cyclophellitol, are selective for HPSE over β-D-exo-glucuronidase (GUSB), also in platelet lysate. The observed selectivity is induced by steric and electrostatic interactions of the substituents at the 4-O-position. Crystallographic analysis supports this rationale for HPSE selectivity, and computer simulations provide insights in the conformational preferences and binding poses of the inhibitors, which we believe are good starting points for the future development of HPSE-targeting antimetastatic cancer drugs

Cysteine Nucleophiles in Glycosidase Catalysis : Application of a Covalent β-L-Arabinofuranosidase Inhibitor

The recent discovery of zinc-dependent retaining glycoside hydrolases (GHs), with active sites built around a Zn(Cys)(3)(Glu) coordination complex, has presented unresolved mechanistic questions. In particular, the proposed mechanism, depending on a Zn-coordinated cysteine nucleophile and passing through a thioglycosyl enzyme intermediate, remains controversial. This is primarily due to the expected stability of the intermediate C-S bond. To facilitate the study of this atypical mechanism, we report the synthesis of a cyclophellitol-derived beta-l-arabinofuranosidase inhibitor, hypothesised to react with the catalytic nucleophile to form a non-hydrolysable adduct analogous to the mechanistic covalent intermediate. This beta-l-arabinofuranosidase inhibitor reacts exclusively with the proposed cysteine thiol catalytic nucleophiles of representatives of GH families 127 and 146. X-ray crystal structures determined for the resulting adducts enable MD and QM/MM simulations, which provide insight into the mechanism of thioglycosyl enzyme intermediate breakdown. Leveraging the unique chemistry of cyclophellitol derivatives, the structures and simulations presented here support the assignment of a zinc-coordinated cysteine as the catalytic nucleophile and illuminate the finely tuned energetics of this remarkable metalloenzyme clan.Medical BiochemistryBio-organic Synthesi

β-L-Arabinofurano-cyclitol Aziridines are Cysteine-directed Broad-spectrum Inhibitors and Activity-based Probes for Retaining β-L-arabinofuranosidases

Bio-organic SynthesisMedical Biochemistr

Microbial enzymes induce colitis by reactivating triclosan in the mouse gastrointestinal tract.

Emerging research supports that triclosan (TCS), an antimicrobial agent found in thousands of consumer products, exacerbates colitis and colitis-associated colorectal tumorigenesis in animal models. While the intestinal toxicities of TCS require the presence of gut microbiota, the molecular mechanisms involved have not been defined. Here we show that intestinal commensal microbes mediate metabolic activation of TCS in the colon and drive its gut toxicology. Using a range of in vitro, ex vivo, and in vivo approaches, we identify specific microbial β-glucuronidase (GUS) enzymes involved and pinpoint molecular motifs required to metabolically activate TCS in the gut. Finally, we show that targeted inhibition of bacterial GUS enzymes abolishes the colitis-promoting effects of TCS, supporting an essential role of specific microbial proteins in TCS toxicity. Together, our results define a mechanism by which intestinal microbes contribute to the metabolic activation and gut toxicity of TCS, and highlight the importance of considering the contributions of the gut microbiota in evaluating the toxic potential of environmental chemicals

A ten-year geographic data set on the occurrence and abundance of macroinvertebrates in the River Po basin (Italy)

Rivers serve many societal functions and are one of the most intensively human influenced ecosystems worldwide, and, due to their importance, are included under the monitoring programs of the Water Framework Directive across Europe. Macroinvertebrates play an important role when monitoring running waters for the assessment of their environmental quality due to their reliability as bioindicators and utility in long-term studies. Macroinvertebrates do not constitute a systematic unit but they are formed by a set of different taxa, grouped according to taxonomic ranks, size and habitat preferences. They represent the base of the aquatic food chain, serving as a food source for amphibians, birds, reptiles, fish and humans, and contributing in the organic matter processing. Despite the large amount of data collected on Italian river macroinvertebrates and the increased interest in the study of this group, only few data are available for research scientist and managers. In this paper, we collected and homogenized knowledge on the presence, distribution and abundances of macroinvertebrates taxa inhabiting the River Po catchment (Northern Italy) in the last decade. The data set includes 130,727 records collected between 2007 and 2018 including 143 taxa of macroinvertebrates, mostly identified at family rank level. Moreover, the data set provides information on the geographic distribution of these families and their abundance by sub-catchment, altitude, meso- and micro-habitat.

A ten-year geographic data set on the occurrence and abundance of macroinvertebrates in the River Po basin (Italy)

Rivers serve many societal functions and are one of the most intensively human influenced ecosystems worldwide, and, due to their importance, are included under the monitoring programs of the Water Framework Directive across Europe. Macroinvertebrates play an important role when monitoring running waters for the assessment of their environmental quality due to their reliability as bioindicators and utility in long-term studies. Macroinvertebrates do not constitute a systematic unit but they are formed by a set of different taxa, grouped according to taxonomic ranks, size and habitat preferences. They represent the base of the aquatic food chain, serving as a food source for amphibians, birds, reptiles, fish and humans, and contributing in the organic matter processing. Despite the large amount of data collected on Italian river macroinvertebrates and the increased interest in the study of this group, only few data are available for research scientist and managers. In this paper, we collected and homogenized knowledge on the presence, distribution and abundances of macroinvertebrates taxa inhabiting the River Po catchment (Northern Italy) in the last decade. The data set includes 130,727 records collected between 2007 and 2018 including 143 taxa of macroinvertebrates, mostly identified at family rank level. Moreover, the data set provides information on the geographic distribution of these families and their abundance by sub-catchment, altitude, meso- and micro-habitat.