Identification, Substrate Specificity, and Inhibition of theStreptococcus pneumoniae β-Ketoacyl-Acyl Carrier Protein Synthase III (FabH)

• Published in: The Journal of biological chemistry Vol. 276; no. 32; p. 30024
• Main Authors: Sanjay S. Khandekar, Daniel R. Gentry, Glenn S. Van Aller, Patrick Warren, Hong Xiang, Carol Silverman, Michael L. Doyle, Pamela A. Chambers, Alex K. Konstantinidis, Martin Brandt, Robert A. Daines, John T. Lonsdale
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 10.08.2001
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M101769200

In the bacterial type II fatty acid synthase system, β-ketoacyl-acyl carrier protein (ACP) synthase III (FabH) catalyzes the condensation of acetyl-CoA with malonyl-ACP. We have identified, expressed, and characterized the Streptococcus pneumoniae homologue of Escherichia coli FabH. S. pneumoniae FabH is ∼41, 39, and 38% identical in amino acid sequence to Bacillus subtilis , E. coli, and Hemophilus influenzae FabH, respectively. The His-Asn-Cys catalytic triad present in other FabH molecules is conserved in S. pneumoniae FabH. The apparent K m values for acetyl-CoA and malonyl-ACP were determined to be 40.3 and 18.6 μ m , respectively. Purified S. pneumoniae FabH preferentially utilized straight short-chain CoA primers. Similar to E. coli FabH, S. pneumoniae FabH was weakly inhibited by thiolactomycin. In contrast, inhibition of S. pneumoniae FabH by the newly developed compound SB418011 was very potent, with an IC 50 value of 0.016 μ m . SB418011 also inhibited E. coli and H. influenzae FabH with IC 50 values of 1.2 and 0.59 μ m , respectively. The availability of purified and characterized S. pneumoniae FabH will greatly aid in structural studies of this class of essential bacterial enzymes and facilitate the identification of small molecule inhibitors of type II fatty acid synthase with the potential to be novel and potent antibacterial agents active against pathogenic bacteria.