Expression of human asparagine synthetase (ASNS) promotes metastatic progression and tumor cell invasiveness in colorectal and breast cancer, presumably by altering cellular levels of L-asparagine. Human ASNS is therefore emerging as a bona fide drug target for cancer therapy. Here we show that a slow-onset, tight binding inhibitor, which exhibits nanomolar affinity for human ASNS in vitro, exhibits excellent selectivity at 10 μM concentration in HCT-116 cell lysates with almost no off-target binding. The high-resolution (1.85 Å) crystal structure of human ASNS has enabled us to identify a cluster of negatively charged side chains in the synthetase domain that plays a key role in inhibitor binding. Comparing this structure with those of evolutionarily related AMP-forming enzymes provides insights into intermolecular interactions that give rise to the observed binding selectivity. Our findings demonstrate the feasibility of developing second generation human ASNS inhibitors as lead compounds for the discovery of drugs against metastasis.

X-Ray crystal structure of a novelC-glycoside synthase involved in the biosynthesis of biologically activeC-nucleosides andC-nucleotides.

P-glycoprotein (Pgp), an ATP binding cassette (ABC) transporter, is an ATP-dependent efflux pump responsible for cancer multidrug resistance. As part of efforts to identify human Pgp (hPgp) inhibitors, we prepared a series of novel triazole-conjugated dihydropyrimidinones using a synthetic approach that is well suited for obtaining compound libraries. Several of these dihydropyrimidinone derivatives modulate human P-glycoprotein (hPgp) activity with low micromolar EC₅₀ values. Molecular docking studies suggest that these compounds bind to the M-site of the transporter.

The biosynthetic enzyme, ForT, catalyses the formation of a C-C bond between 4-amino-1 H -pyrazoledicarboxylic acid and MgPRPP to produce a C-nucleoside precursor of formycin A. The transformation catalysed by ForT is of chemical interest because it is one of only a few examples in which C-C bond formation takes place via an electrophilic substitution of a small, aromatic heterocycle. In addition, ForT is capable of discriminating between the aminopyrazoledicarboxylic acid and an analogue in which the amine is replaced by a hydroxyl group; a remarkable feat given the steric and electronic similarities of the two molecules. Here we report biophysical measurements, structural biology and quantum chemical calculations that provide a detailed molecular picture of ForT-catalysed C-C bond formation and the conformational changes that are coupled to catalysis. Our findings set the scene for employing engineered ForT variants in the biocatalytic production of novel, anti-viral C-nucleoside and C-nucleotide analogues.

Interactions relating to human chemical signalling, although widely acknowledged, are relatively poorly characterized chemically, except for human axillary odour. However, the extensive chemical ecology of insects, involving countless pheromone and other semiochemical identifications, may offer insights into overcoming problems of characterizing human-derived semiochemicals more widely. Current techniques for acquiring insect semiochemicals are discussed, particularly in relation to the need for samples to relate, as closely as possible, to the ecological situation in which they are naturally deployed. Analysis is facilitated by chromatography coupled to electrophysiological preparations from the olfactory organs of insects in vivo . This is not feasible with human olfaction, but there are now potential approaches using molecular genetically reconstructed olfactory preparations already in use with insect systems. There are specific insights of value for characterizing human semiochemicals from advanced studies on semiochemicals of haematophagous insects, which include those involving human hosts, in addition to wider studies on farm and companion animals. The characterization of the precise molecular properties recognized in olfaction could lead to new advances in analogue design and a range of novel semiochemicals for human benefit. There are insights from successful synthetic biology studies on insect semiochemicals using novel biosynthetic precursors. Already, wider opportunities in olfaction emerging from in silico studies, involving a range of theoretical and computational approaches to molecular design and understanding olfactory systems at the molecular level, are showing promise for studying human semiochemistry. This article is part of the Theo Murphy meeting issue ‘ Olfactory communication in humans ’.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.