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Interaction of Antimycobacterial Drugs with the Anti-Mycobacterium avium Complex Effects of Antimicrobial Effectors, Reactive Oxygen Intermediates, Reactive Nitrogen Intermediates, and Free Fatty Acids Produced by Macrophages. Keisuke Sano, 2004.The profiles of the interaction of antimycobacterial drugs with macrophage (M  ) antimicrobial mechanisms have yet to be elucidated in detail . We examined the effects of various antimycobacterial drugs on the anti-Mycobacterium avium complex (MAC) antimicrobial activity of reactive oxygen intermediates (ROIs), especially of an H2O2-halogen (H2O2-Fe2+-NaI)-mediated bactericidal system, reactive nitrogen intermediates (RNIs), and free fatty acids (FFAs), which are known as central antimicrobial effectors of host Ms against mycobacterial pathogens . We have found that certain drugs, such as rifampin (RIF), rifabutin (RFB), isoniazid (INH), clofazimine (CLO), and some fluoroquinolones, strongly or moderately reduced the anti-MAC activity of the H2O2-Fe2+-NaI system, primarily by inhibiting the generation of hypohalite ions and in part by interfering with the halogenation reaction of bacterial cell components due to the H2O2-Fe2+-NaI system . This phenomenon is specific to the H2O2-Fe2+-NaI system, since these drugs did not reduce the anti-MAC activity of RNIs and FFAs . From the perspective of the chemotherapy of MAC infections, the present findings indicate an important possibility that certain antimycobacterial drugs, such as rifamycins (RIF and RFB), INH, CLO, and also some types of fluoroquinolones, may interfere with the ROI-mediated antimicrobial mechanisms of host Ms against intracellular MAC organisms .
Plasmid R16 ArdA Protein Preferentially Targets Restriction Activity of the Type I Restriction-Modification System EcoKI. Angela T. Thomas, 2003.The ArdA antirestriction protein of the IncB plasmid R16 selectively inhibited the restriction activity of EcoKI, leaving significant levels of modification activity under conditions in which restriction was almost completely prevented . The results are consistent with the hypothesis that ArdA functions in bacterial conjugation to allow an unmodified plasmid to evade restriction in the recipient bacterium and yet acquire cognate modification . Vibrio harveyi Nitroreductase Is Also a Chromate Reductase. Young Hak Kwak, 2003.The chromate reductase purified from Pseudomonas ambigua was found to be homologous with several nitroreductases . Escherichia coli DH5  and Vibrio harveyi KCTC 2720 nitroreductases were chosen for the present study, and their chromate-reducing activities were determined . A fusion between glutathione S-transferase (GST) and E . coli DH5 NfsA (GST-EcNfsA), a fusion between GST and E . coli DH5 NfsB (GST-EcNfsB), and a fusion between GST and V . harveyi KCTC 2720 NfsA (GST-VhNfsA) were prepared for their overproduction and easy purification . GST-EcNfsA, GST-EcNFsB, and GST-VhNFsA efficiently reduced nitrofurazone and 2,4,6-trinitrotoluene (TNT) as their nitro substrates . The Km values for GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA for chromate reduction were 11.8, 23.5, and 5.4 µM, respectively . The Vmax values for GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA were 3.8, 3.9, and 10.7 nmol/min/mg of protein, respectively . GST-VhNfsA was the most effective of the three chromate reductases, as determined by each Vmax/Km value . The optimal temperatures of GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA for chromate reduction were 55, 30, and 30°C, respectively . Thus, it is confirmed that nitroreductase can also act as a chromate reductase . Nitroreductases may be used in chromate remediation . GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA have a molecular mass of 50 kDa and exist as a monomer in solution . Thin-layer chromatography showed that GST-EcNfsA, GST-EcNfsB, and GST-VhNfsA contain FMN as a cofactor . GST-VhNfsA reduced Cr(VI) to Cr(III) . Cr(III) was much less toxic to E . coli than Cr(VI) .
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