ИСТИНА

The treatment of bacterial infection using beta-lactam antibiotics, including penicillin and cephalosporin compounds, is currently limited by bacterial resistance to these agents, typically caused by beta-lactamase enzymes. More than 800 mutations have been identified in enzymes of this type. Existing inhibitors of beta-lactamases can prevent antibiotic degradation arising from beta-lactam ring hydrolysis, but due to the additional development of resistance to these compounds, they are not sufficiently effective. Thus, the identification of new inhibitors and new mechanisms of lactamase inhibition is a priority. To address this challenge, we computationally screened 8 million organic molecules using the ViCi software (http://www.emblhamburg.de/vici), which we specially developed for this purpose. The software permits the rapid screening against a known inhibitor template and selects the closest matching compounds in terms of shape and electrostatic composition. Four known low-affinity lactamase inhibitors were given to the software as a starting point. Recombinant TEM-1 enzyme was produced and used to assay 550 of the top compounds suggested by ViCi screening. Five new inhibitors were identified, the best having an order of magnitude higher in vitro affinity for the enzyme than its template. Intriguingly, two of these are predicted to be allosteric inhibitors and three others are based on inhibitors of CTX-M-9, suggesting that cross-inhibition of different isoforms may be possible. The inhibition was confirmed in vivo. X-ray crystal structure determination of the structures of native enzyme and its complexes with ligands is now in progress. The ViCi software is being improved to accept multiple templates and will be used to suggest compounds for the next iteration of screening. Docking protocols, validated by crystallography, may be used to refine the results, aiding our rapid convergence to more avidly binding compounds. The current status of the X-ray crystallographic, computational and laboratory studies will be presented.