α-L-Arabinofuranosylated pyrrolidines as arabinanase inhibitors.

As part of continued efforts to understand the mechanisms of 1,5-α-l-arabinanases better, some arabinan-like iminosugar oligosaccharides were synthesized. An iminosugar analogue of arabinobiose was found to be a good inhibitor of the arabinanase Arb93A from Fusarium graminearum. Structures were determined for complexes of this inhibitor with wild-type Arb93A and a catalytically inactive mutant.

Structure-activity relationship of karrikin germination stimulants.

Karrikins (2H-furo[2,3-c]pyran-2-ones) are potent smoke-derived germination promoters for a diverse range of plant species but, to date, their mode of action remains unknown. This paper reports the structure-activity relationship of numerous karrikin analogues to increase understanding of the key structural features of the molecule that are required for biological activity. The results demonstrate that modification at the C5 position is preferred over modification at the C3, C4, or C7 positions for retaining the highest bioactivity.

The synthesis and biological evaluation of some carbocyclic analogues of PUGNAc.

The synthesis of some analogues of O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino N-phenylcarbamate, PUGNAc, an inhibitor of β-N-acetylglucosaminidases, is described. The analogues were tested against a range of β-N-acetylglucosaminidases to establish any biological activity. As well, the analogues were tested as inhibitors of a uridine diphosphate-N-acetyl-D-glucosamine: polypeptidyl transferase, OGT, a critical protein involved in the post-translational modification of nuclear and cytosolic proteins by N-acetyl-d-glucosamine.

Structural and biochemical evidence for a boat-like transition state in beta-mannosidases.

Enzyme inhibition through mimicry of the transition state is a major area for the design of new therapeutic agents. Emerging evidence suggests that many retaining glycosidases that are active on alpha- or beta-mannosides harness unusual B2,5 (boat) transition states. Here we present the analysis of 25 putative beta-mannosidase inhibitors, whose Ki values range from nanomolar to millimolar, on the Bacteroides thetaiotaomicron beta-mannosidase BtMan2A.

Synthesis and use of mechanism-based protein-profiling probes for retaining beta-D-glucosaminidases facilitate identification of Pseudomonas aeruginosa NagZ.

The NagZ class of retaining exo-glucosaminidases play a critical role in peptidoglycan recycling in Gram-negative bacteria and the induction of resistance to beta-lactams. Here we describe the concise synthesis of 2-azidoacetyl-2-deoxy-5-fluoro-beta-d-glucopyranosyl fluoride as an activity-based proteomics probe for profiling these exo-glycosidases. This active-site directed reagent covalently inactivates this class of retaining N-acetylglucosaminidases with exquisite selectivity by stabilizing the glycosyl-enzyme intermediate.

A 1-acetamido derivative of 6-epi-valienamine: an inhibitor of a diverse group of beta-N-acetylglucosaminidases.

The synthesis of an analogue of 6-epi-valienamine bearing an acetamido group and its characterisation as an inhibitor of beta-N-acetylglucosaminidases are described. The compound is a good inhibitor of both human O-GlcNAcase and human beta-hexosaminidase, as well as two bacterial beta-N-acetylglucosaminidases. A 3-D structure of the complex of Bacteroides thetaiotaomicron BtGH84 with the inhibitor shows the unsaturated ring is surprisingly distorted away from its favoured solution phase conformation and reveals potential for improved inhibitor potency.

An efficient, inexpensive, and shelf-stable diazotransfer reagent: imidazole-1-sulfonyl azide hydrochloride.

The design and synthesis of a new diazotransfer reagent, imidazole-1-sulfonyl azide hydrochloride, are reported. This reagent has proven to equal triflyl azide in its ability to act as a "diazo donor" in the conversion of both primary amines into azides and activated methylene substrates into diazo compounds. Crucially, this reagent can be prepared in a one-pot reaction on a large scale from inexpensive materials, is shelf-stable, and is conveniently crystalline.

The synthesis of 2-, 3-, 4- and 6-O-alpha-D-glucopyranosyl-D-galactopyranose, and their evaluation as nutritional supplements for pre-term infants.

Four methods have been screened for the synthesis of some alpha-D-glucopyranosides, with the recently reported (Mukaiyama) combination of 2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl iodide and triphenylphosphine oxide being the most successful, especially in the diastereoselectivity exhibited. The alpha-D-glucopyranosides so obtained have been deprotected to yield 2-, 3-, 4- and 6-O-alpha-D-glucopyranosyl-D-galactopyranose. Only the last disaccharide showed any hydrolysis by alpha-glycosidases but this success was not emulated by mucosal extracts from the small intestine of the pig.

Glycosidase inhibition: an assessment of the binding of 18 putative transition-state mimics.

The inhibition of glycoside hydrolases, through transition-state mimicry, is important both as a probe of enzyme mechanism and in the continuing quest for new drugs, notably in the treatment of cancer, HIV, influenza, and diabetes. The high affinity with which these enzymes are known to bind the transition state provides a framework upon which to design potent inhibitors. Recent work [for example, Bülow, A.

Carbohydrate-bearing 3-hydroxy-4-pyridinonato complexes of gallium(III) and indium(III).

Gallium and indium complexes with pendant carbohydrates have been prepared and examined for their potential as radiopharmaceuticals. Carbohydrate-bearing 3-hydroxy-4-pyridinone ligand precursors and their tris(ligand)gallium(III) and -indium(III) complexes were synthesized and characterized by mass spectrometry, elemental analysis, and (1)H and (13)C NMR spectroscopy, and in the case of one intermediate, by X-ray crystallography. With three equivalents of ligand, neutral complexes formed with the bidentate hydroxypyridinone moiety complexing the gallium(III) and indium(III) metal centers.

How family 26 glycoside hydrolases orchestrate catalysis on different polysaccharides: structure and activity of a Clostridium thermocellum lichenase, CtLic26A.

One of the most intriguing features of the 90 glycoside hydrolase families (GHs) is the range of specificities displayed by different members of the same family, whereas the catalytic apparatus and mechanism are often invariant. Family GH26 predominantly comprises beta-1,4 mannanases; however, a bifunctional Clostridium thermocellum GH26 member (hereafter CtLic26A) displays a markedly different specificity. We show that CtLic26A is a lichenase, specific for mixed (Glcbeta1,4Glcbeta1,4Glcbeta1,3)n oligo- and polysaccharides, and displays no activity on manno-configured substrates or beta-1,4-linked homopolymers of glucose or xylose.

Mycobacterium tuberculosis strains possess functional cellulases.

The genomes of various Mycobacterium tuberculosis strains encode proteins that do not appear to play a role in the growth or survival of the bacterium in its mammalian host, including some implicated in plant cell wall breakdown. Here we show that M. tuberculosis H37Rv does indeed possess a functional cellulase.

Structural, thermodynamic, and kinetic analyses of tetrahydrooxazine-derived inhibitors bound to beta-glucosidases.

The understanding of transition state mimicry in glycoside hydrolysis is increasingly important both in the quest for novel specific therapeutic agents and for the deduction of enzyme function and mechanism. To aid comprehension, inhibitors can be characterized through kinetic, thermodynamic, and structural dissection to build an "inhibition profile." Here we dissect the binding of a tetrahydrooxazine inhibitor and its derivatives, which display Ki values around 500 nm.

Iminosugar glycosidase inhibitors: structural and thermodynamic dissection of the binding of isofagomine and 1-deoxynojirimycin to beta-glucosidases.

The design and synthesis of transition-state mimics reflects the growing need both to understand enzymatic catalysis and to influence strategies for therapeutic intervention. Iminosugars are among the most potent inhibitors of glycosidases. Here, the binding of 1-deoxynojirimycin and (+)-isofagomine to the "family GH-1" beta-glucosidase of Thermotoga maritima is investigated by kinetic analysis, isothermal titration calorimetry, and X-ray crystallography.

Direct observation of the protonation state of an imino sugar glycosidase inhibitor upon binding.

Glycosidases are some of the most ubiquitous enzyme in nature. Their biological significance, coupled to their enormous catalytic prowess derived from tight binding of the transition state, is reflected in their importance as therapeutic targets. Many glycosidase inhibitors are known.

Distortion of a cellobio-derived isofagomine highlights the potential conformational itinerary of inverting beta-glucosidases.

A cellobio-derived isofagomine glycosidase inhibitor (Ki approximately 400 nM) displays an unusual distorted 2,5B (boat) conformation upon binding to cellobiohydrolase Cel6A from Humicola insolens, highlighting the different conformational itineraries used by various glycosidases, with consequences for the design of therapeutic agents.