Lipopolysaccharide (LPS)1, an essential structure in the outer membrane (OM) of Gram-negative bacteria, is a key structure that is sensed by the host, representing a potent stimulant of the innate immune response.
3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) is always present in all LPS’s inner cores analyzed2 and it is a fundamental compound for bacterial survival3. We highlight KdsD, arabinose phosphate isomerase (API), a relevant target as it catalyses the first step of Kdo biosynthesis4. As this process is unique to Gram-negative bacteria, it represents an excellent target for drug development.
Previous NMR studies on the structural requirements necessary for KdsD substrate’s recognition5 showed that the acidic phosphate group is fundamental for binding, and API is able to recognize substrates in their cyclic form. Based on these observations, we report the synthesis of fluorinated A5P analogues: α and β Fluoro-Arabinosides were modified in position 5 with the natural phosphate group or a phosphate’s mimetic. A difluoromethylphosphonate A5P analogue was synthesised as well.
We performed STD-NMR studies on the synthesised compounds to investigate their interaction with API. In addition the biological activity was assayed in vivo on E. Coli, and P. Areuginosa.
References.
1. Christian et al., Annu. Rev. Biochem. 2002, 71, 635–700.
2. Holst et al., Comprehensive Glycoscience, Elsevier, 2007, 123–179.
3. Cipolla, et al., Nat. Prod. Rep., 2010, 27, 1618–1629
4. a) Meredith, et al., Journal of Biological Chemistry, 2003, 278, 32771-32777; b) Sperandeo et al., Res. Microbiol., 2006, 157, 547-558
5. C. Airoldi, et al., Chemistry, Eur. J. 2010, 16, 1897-1902.
Aknowledgments. We gratefully acknowledge MIUR, under project PRIN2008/24M2HX, FINLOMBARDA-Regione Lombardia Fondo per la promozione di Accordi Istituzionali- 2009 under project "Rational Drug Design to target outer membrane biogenesis of Gram-negative pathogenic bacteria", and Fondazione Cariplo, grant n° 2010-0653.
