title: A novel combinatorial biocatalytic approach for producing antibacterial compounds effective against Mycobacterium tuberculosis (TB).
abstract: Two bacterial hosts expressing cloned aromatic oxygenases were used to catalyze the oxidation and polymerization of indole and related substrates, creating mixtures of indigoid compounds comprised of novel dimers and trimers. Crude extracts and purified compounds were tested for their ability to inhibit the growth of Gram-positive organisms, in general, and Mycobacterium tuberculosis (TB), in particular. Of the 74 compounds tested against M. tuberculosis, ~66 % had minimum inhibitory concentrations (MIC) of 5 μg/ml or less. The most effective antibiotic found was designated SAB-P1, a heterodimer of indole and anthranil, which had a MIC of 0.16 μg/ml, and did not inhibit kidney cells (IC(50)) at concentrations of >8 μg/ml. Combinatorial biocatalysis was used to create a series of halogenated derivatives of SAB-P1 with a wider therapeutic window. None of the derivatives had MIC values that were superior to SAB-P1, but some had a wider therapeutic window because of decreased kidney cell toxicity. Generally, the indigoid dimers that were effective against TB appeared to be specific for TB. Some of the trimers generated, however, had a broader spectrum of activity inhibiting not only TB (MIC = 1.1 μg/ml) but also the growth of Mycobacterium smegmatis MC2 155, Bacillus cereus, Enterococcus faecalis, Staphylococcus epidermidis, Bacillus subtilis 168, and Clostridium acetobutylicum. The structure of two of the novel dimers (SAB-C4 and SAB-P1) and a trimer (SAB-R1) were solved using X-ray crystallography.
authors.affiliation: CB&I, 17 Princess Rd., Lawrenceville, NJ 08648, USA. Kevin.mcclay@cbifederalservices.com
authors.forename: Kevin
authors.initials: K
authors.lastname: McClay
authors.forename: Baojie
authors.initials: B
authors.lastname: Wan
authors.forename: Yuehong
authors.initials: Y
authors.lastname: Wang
authors.forename: Sanghyun
authors.initials: S
authors.lastname: Cho
authors.forename: Jerry
authors.initials: J
authors.lastname: Yu
authors.forename: Bernard
authors.initials: B
authors.lastname: Santarsiero
authors.forename: Shahila
authors.initials: S
authors.lastname: Mehboob
authors.forename: Michael
authors.initials: M
authors.lastname: Johnson
authors.forename: Scott
authors.initials: S
authors.lastname: Franzblau
authors.forename: Robert
authors.initials: R
authors.lastname: Steffan
mesh_terms: D000995:Antitubercular Agents / Q000302:isolation & purification / Q000378:metabolism* / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006094:Gram-Positive Bacteria / Q000187:drug effects; D006801:Humans; D007211:Indoles / Q000302:isolation & purification / Q000378:metabolism* / Q000633:toxicity; D020128:Inhibitory Concentration 50; D008826:Microbial Sensitivity Tests; D009169:Mycobacterium tuberculosis / Q000187:drug effects*
chemical_list: D000995:Antitubercular Agents; D007211:Indoles