ANN ARBOR---Building on recent discovery of a potent potential antibiotic, University of Michigan College of Pharmacy researchers have found a previously unknown family of metal-requiring enzymes in bacteria. They have also demonstrated that the antibiotic compound they are studying effectively inhibits enzymes in this family.
The latest work by Prof. Ronald Woodard and colleagues follows from research they reported in the Sept. 27, 2000, Journal of the American Chemical Society. In that project, the researchers screened some 150,000 compounds and found one, PD 404182, that was 10,000 times more effective than other known inhibitors of a key enzyme in Gram negative bacteria. The compound targets the enzyme KDO 8-P synthase, which plays a vital role in the formation of antenna-like lipopolysaccharides on the surfaces of bacterial cells. Lipopolysaccharides have numerous functions---helping bacteria defend themselves against host immune responses, for example.
The new research focuses on the target enzyme, KDO 8-P synthase. Collaborating with Prof. Domenico L. Gatti at Wayne State University School of Medicine, Woodard's group had previously determined the crystal structure of the enzyme in the bacterium E. coli. However, it was impossible to use those crystals to observe how PD404182 binds to the active site of KDO 8-P synthase, because the holding solution in which KDO 8-P synthase crystals are stable contains high concentrations of salt, which interfere with binding.
To get around that problem, Woodard's group isolated and crystallized KDO 8-P synthase from another bacterium, Aquifex aeolicus, which lives at high temperatures in hydrothermal vents. A. aeolicus does not cause human disease, but can serve as a useful model for pathogenic organisms. Because the A. aeolicus enzyme is active only at high temperatures, the researchers could introduce substrates to the crystallized enzyme at lower temperatures without causing a complete reac
Contact: Nancy Ross-Flanigan
University of Michigan