Glycosyl hydrolases (GHs) are carbohydrate-active enzymes that hydrolyze a specific β-glycosidic bond in glycoconjugate substrates; β-glucosidases degrade glucosylceramide, a ubiquitous... Show moreGlycosyl hydrolases (GHs) are carbohydrate-active enzymes that hydrolyze a specific β-glycosidic bond in glycoconjugate substrates; β-glucosidases degrade glucosylceramide, a ubiquitous glycosphingolipid. GHs are grouped into structurally similar families that themselves can be grouped into clans. GH1, GH5, and GH30 glycosidases belong to clan A hydrolases with a catalytic (β/α)8 TIM barrel domain, whereas GH116 belongs to clan O with a catalytic (α/α)6 domain. In humans, GH abnormalities underlie metabolic diseases. The lysosomal enzyme glucocerebrosidase (family GH30), deficient in Gaucher disease and implicated in Parkinson disease etiology, and the cytosol-facing membrane-bound glucosylceramidase (family GH116) remove the terminal glucose from the ceramide lipid moiety. Here, we compare enzyme differences in fold, action, dynamics, and catalytic domain stabilization by binding site occupancy. We also explore other glycosidases with reported glycosylceramidase activity, including human cytosolic β-glucosidase, intestinal lactase-phlorizin hydrolase, and lysosomal galactosylceramidase. Last, we describe the successful translation of research to practice: recombinant glycosidases and glucosylceramide metabolism modulators are approved drug products (enzyme replacement therapies). Activity-based probes now facilitate the diagnosis of enzyme deficiency and screening for compounds that interact with the catalytic pocket of glycosidases. Future research may deepen the understanding of the functional variety of these enzymes and their therapeutic potential. Show less
Basler, M.; Lindstrom, M.M.; LaStant, J.J.; Bradshaw, J.M.; Owens, T.D.; Schmidt, C.; ... ; Groettrup, M. 2018
Cells of hematopoietic origin express high levels of the immunoproteasome, a cytokine-inducible proteasome variant comprising the proteolytic subunits LMP2 (β1i), MECL-1 (β2i), and LMP7 (β5i).... Show moreCells of hematopoietic origin express high levels of the immunoproteasome, a cytokine-inducible proteasome variant comprising the proteolytic subunits LMP2 (β1i), MECL-1 (β2i), and LMP7 (β5i). Targeting the immunoproteasome in pre-clinical models of autoimmune diseases with the epoxyketone inhibitor ONX 0914 has proven to be effective. ONX 0914 was previously described as a selective LMP7 inhibitor. Here, we show that PRN1126, developed as an exclusively LMP7-specific inhibitor, has limited effects on IL-6 secretion, experimental colitis, and experimental autoimmune encephalomyelitis (EAE). We demonstrate that prolonged exposure of cells with ONX 0914 leads to inhibition of both LMP7 and LMP2. Co-inhibition of LMP7 and LMP2 with PRN1126 and LMP2 inhibitors LU-001i or ML604440 impairs MHC class I cell surface expression, IL-6 secretion, and differentiation of naïve T helper cells to T helper 17 cells, and strongly ameliorates disease in experimental colitis and EAE. Hence, co-inhibition of LMP2 and LMP7 appears to be synergistic and advantageous for the treatment of autoimmune diseases. Show less
Tol, M.J.; Lienden, M.J.C. van der; Gabriel, T.L.; Hagen, J.J.; Scheij, S.; Veenendaal, T.; ... ; Eijk, M.C. van 2018
Iminosugars are an important class of natural products and have been subject to extensive studies in organic synthesis, bioorganic chemistry and medicinal chemistry, yet only a limited number of... Show moreIminosugars are an important class of natural products and have been subject to extensive studies in organic synthesis, bioorganic chemistry and medicinal chemistry, yet only a limited number of these studies are on glycosylated iminosugars. Here, a general route of synthesis is presented towards glycosylated 1‐deoxynojirimycin derivatives based on the oxidation–reductive amination protocol that in the past has also been shown to be a versatile route towards 1‐deoxynojirimycin. The strategy can be applied on commercial disaccharides, as shown in four examples, as well as on disaccharides that are not commercially available and are synthesized for this purpose, as shown by a fifth example. Show less
Cyclophellitol aziridines are potent irreversible inhibitors of retaining glycosidases and versatile intermediates in the synthesis of activity‐based glycosidase probes (ABPs). Direct 3‐amino‐2‐... Show moreCyclophellitol aziridines are potent irreversible inhibitors of retaining glycosidases and versatile intermediates in the synthesis of activity‐based glycosidase probes (ABPs). Direct 3‐amino‐2‐(trifluoromethyl)quinazolin‐4(3H)‐one‐mediated aziridination of l‐ido‐configured cyclohexene has enabled the synthesis of new covalent inhibitors and ABPs of α‐l‐iduronidase, deficiency of which underlies the lysosomal storage disorder mucopolysaccharidosis type I (MPS I). The iduronidase ABPs react covalently and irreversibly in an activity‐based manner with human recombinant α‐l‐iduronidase (rIDUA, Aldurazyme®). The structures of IDUA when complexed with the inhibitors in a non‐covalent transition state mimicking form and a covalent enzyme‐bound form provide insights into its conformational itinerary. Inhibitors 1–3 adopt a half‐chair conformation in solution (4H3 and 3H4), as predicted by DFT calculations, which is different from the conformation of the Michaelis complex observed by crystallographic studies. Consequently, 1–3 may need to overcome an energy barrier in order to switch from the 4H3 conformation to the transition state (2, 5B) binding conformation before reacting and adopting a covalent 5S1 conformation. rIDUA can be labeled with fluorescent Cy5 ABP 2, which allows monitoring of the delivery of therapeutic recombinant enzyme to lysosomes, as is intended in enzyme replacement therapy for the treatment of MPS I patients. Show less
The inverse-electron-demand Diels-Alder/pyridazine elimination tandem reaction, in which the allylic substituent on trans-cyclooctene is eliminated following reaction with tetrazines, is gaining... Show moreThe inverse-electron-demand Diels-Alder/pyridazine elimination tandem reaction, in which the allylic substituent on trans-cyclooctene is eliminated following reaction with tetrazines, is gaining interest as a versatile bioorthogonal process. One potential shortcoming of such currently used reactions is their propensity to proceed faster and more efficiently at lower pH, a feature caused by the nature of the tetrazines used. Here, we present aminoethyl-substituted tetrazines as the first pH-independent reagents showing invariably fast elimination kinetics at all biologically relevant pH values. Show less
Bioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality that might be present. Recent developments in the field include... Show moreBioorthogonal chemistry can be used for the selective modification of biomolecules without interfering with any other functionality that might be present. Recent developments in the field include orthogonal bioorthogonal reactions to modify multiple biomolecules simultaneously. During our research, we observed that the reaction rates for the bioorthogonal inverse‐electron‐demand Diels–Alder (iEDDA) reactions between nonstrained vinylboronic acids (VBAs) and dipyridyl‐s‐tetrazines were exceptionally higher than those between VBAs and tetrazines bearing a methyl or phenyl substituent. As VBAs are mild Lewis acids, we hypothesised that coordination of the pyridyl nitrogen atom to the boronic acid promoted tetrazine ligation. Herein, we explore the molecular basis and scope of VBA–tetrazine ligation in more detail and benefit from its unique reactivity in the simultaneous orthogonal tetrazine labelling of two proteins modified with VBA and norbornene, a widely used strained alkene. We further show that the two orthogonal iEDDA reactions can be performed in living cells by labelling the proteasome by using a nonselective probe equipped with a VBA and a subunit‐selective VBA bearing a norbornene moiety. Show less
Voorneveld, J.; Rack, J.G.M.; Ahel, I.; Overkleeft, H.S.; Marel, G.A. van der; Filippov, D.V. 2018
The endocannabinoid system (ECS) is considered to be an endogenous protective system in various neurodegenerative diseases. Niemann-Pick type C (NPC) is a neurodegenerative disease in which the... Show moreThe endocannabinoid system (ECS) is considered to be an endogenous protective system in various neurodegenerative diseases. Niemann-Pick type C (NPC) is a neurodegenerative disease in which the role of the ECS has not been studied yet. Most of the endocannabinoid enzymes are serine hydrolases, which can be studied using activity-based protein profiling (ABPP). Here, we report the serine hydrolase activity in brain proteomes of a NPC mouse model as measured by ABPP. Two ABPP methods are used: a gel-based method and a chemical proteomics method. The activities of the following endocannabinoid enzymes were quantified: diacylglycerol lipase (DAGL) α, α/β-hydrolase domain-containing protein 4, α/β-hydrolase domain-containing protein 6, α/β-hydrolase domain-containing protein 12, fatty acid amide hydrolase, and monoacylglycerol lipase. Using the gel-based method, two bands were observed for DAGL α. Only the upper band corresponding to this enzyme was significantly decreased in the NPC mouse model. Chemical proteomics showed that three lysosomal serine hydrolase activities (retinoid-inducible serine carboxypeptidase, cathepsin A, and palmitoyl-protein thioesterase 1) were increased in Niemann-Pick C1 protein knockout mouse brain compared to wild-type brain, whereas no difference in endocannabinoid hydrolase activity was observed. We conclude that these targets might be interesting therapeutic targets for future validation studies. Show less
Vorm, S. van der; Hengst, J.M.A. van; Bakker, M.H.E.; Overkleeft, H.S.; Marel, G.A. van der; Codee, J.D.C. 2018
Activation of a cytotoxic T-cell is a complex multistep process, and tools to study the molecular events and their dynamics that result in T-cell activation in situ and in vivo are scarce. Here, we... Show moreActivation of a cytotoxic T-cell is a complex multistep process, and tools to study the molecular events and their dynamics that result in T-cell activation in situ and in vivo are scarce. Here, we report the design and use of conditional epitopes for time-controlled T-cell activation in vivo. We show that trans-cyclooctene-protected SIINFEKL (with the lysine amine masked) is unable to elicit the T-cell response characteristic for the free SIINFEKL epitope. Epitope uncaging by means of an inverse-electron demand Diels–Alder (IEDDA) event restored T-cell activation and provided temporal control of T-cell proliferation in vivo. Show less
Diacylglycerol lipases (DAGL) are responsible for the biosynthesis of the endocannabinoid 2‐arachidonoylglycerol. The fluorescent activity‐based probes DH379 and HT‐01 have been previously shown to... Show moreDiacylglycerol lipases (DAGL) are responsible for the biosynthesis of the endocannabinoid 2‐arachidonoylglycerol. The fluorescent activity‐based probes DH379 and HT‐01 have been previously shown to label DAGLs and to cross‐react with the serine hydrolase ABHD6. Here, we report the synthesis and characterization of two new quenched activity‐based probes 1 and 2, the design of which was based on the structures of DH379 and HT‐01, respectively. Probe 1 contains a BODIPY‐FL and a 2,4‐dinitroaniline moiety as a fluorophore–quencher pair, whereas probe 2 employs a Cy5‐fluorophore and a cAB40‐quencher. The fluorescence of both probes was quenched with relative quantum yields of 0.34 and 0.0081, respectively. The probes showed target inhibition as characterized in activity‐based protein profiling assays using human cell‐ and mouse brain lysates, but were unfortunately not active in living cells, presumably due to limited cell permeability. Show less
Engelsma, S.B.; Ende, T.C. van den; Overkleeft, H.S.; Marel, G.A. van der; Filippov, D.V. 2018
