Determination of selectivity and efficacy of fatty acid synthesis inhibitors.
Type II fatty acid synthesis (FASII) is essential to bacterial cell viability and is a promising target for the development of novel antibiotics. In the past decade, a few inhibitors have been identified for this pathway, but none of them lend themselves to drug development. To find better inhibitors that are potential drug candidates, we developed a high throughput assay that identifies inhibitors simultaneously against multiple targets within the FASII pathway of most bacterial pathogens. We demonstrated that the inverse t(1/2) value of the FASII enzyme-catalyzed reaction gives a measure of FASII activity. The Km values of octanoyl-CoA and lauroyl-CoA were determined to be 1.1 +/- 0.3 and 10 +/- 2.7 microM in Staphylococcus aureus and Bacillus subtilis, respectively. The effects of free metals and reducing agents on enzyme activity showed an inhibition hierarchy of Zn2+ > Ca2+ > Mn2+ > Mg2+; no inhibition was found with beta-mercaptoethanol or dithiothreitol. We used this assay to screen the natural product libraries and isolated an inhibitor, bischloroanthrabenzoxocinone (BABX) with a new structure. BABX showed IC50 values of 11.4 and 35.3 microg/ml in the S. aureus and Escherichia coli FASII assays, respectively, and good antibacterial activities against S. aureus and permeable E. coli strains with minimum inhibitory concentrations ranging from 0.2 to 0.4 microg/ml. Furthermore, the effectiveness, selectivity, and the in vitro and in vivo correlations of BABX as well as other fatty acid inhibitors were elucidated, which will aid in future drug discovery.
Kodali
Srinivas
S
Department of Human and Animal Infectious Disease, Merck Research Laboratories, Rahway, New Jersey 07065, USA.
Galgoci
Andrew
A
Young
Katherine
K
Painter
Ronald
R
Silver
Lynn L
LL
Herath
Kithsiri B
KB
Singh
Sheo B
SB
Cully
Doris
D
Barrett
John F
JF
Schmatz
Dennis
D
Wang
Jun
J
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D002413:Cations, Divalent / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D005227:Fatty Acids / Q000096:biosynthesis*; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008623:Mercaptoethanol / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D012680:Sensitivity and Specificity; D013379:Substrate Specificity
D000900:Anti-Bacterial Agents; D002413:Cations, Divalent; D005227:Fatty Acids; D006576:Heterocyclic Compounds, 4 or More Rings; C496714:bischloroanthrabenzoxocinone; D008623:Mercaptoethanol; D004229:Dithiothreitol