title: Inhibition and kinetics of mycobacterium tuberculosis and mycobacterium smegmatis mycothiol-S-conjugate amidase by natural product inhibitors.
abstract: The current rise in mycobacterial-related infections and disease, coupled with drug resistance, underlines the continuing need for new antimycobacterials. To this end, we have screened approximately 1500 extracts derived from marine plants and invertebrates and terrestrial fungi for their ability to inhibit a newly described mycobacterial detoxification enzyme mycothiol-S-conjugate amidase (MCA). As described in this paper, our screening and chemistry efforts thus far have led to the identification of 13 natural product inhibitors that represent six different structural classes. By conducting enzyme inhibition assays using varied inhibitor and substrate concentrations, we have determined the mode of inhibition of Mycobacterium tuberculosis MCA for four of these compounds. We show that two types of bromotyrosine-derived natural products are competitive inhibitors of MCA; while oceanapiside, an alpha,omega-bis-aminohydroxy glycosphingolipid, and the fungal metabolite gliotoxin, a dithiadiketopiperazine, are simple and mixed non-competitive inhibitors, respectively. Correlation of these results with the chemical structures suggests that MCA is a metalloenzyme and that the oximinoamide and spiro-isoxazoline amide groups present in the competitive inhibitors are substrate mimics.
authors.affiliation: Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, 20892-0820, Bethesda, MD, USA.
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Nicholas
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Eckman
authors.forename: Gerald L
authors.initials: GL
authors.lastname: Newton
authors.forename: Robert C
authors.initials: RC
authors.lastname: Fahey
authors.forename: Satyajit
authors.initials: S
authors.lastname: Ray
authors.forename: Carole A
authors.initials: CA
authors.lastname: Bewley
mesh_terms: D000581:Amidohydrolases / Q000037:antagonists & inhibitors*; D000818:Animals; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents / Q000494:pharmacology*; D001230:Aspergillus / Q000737:chemistry; D001685:Biological Factors / Q000494:pharmacology*; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005658:Fungi / Q000737:chemistry; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008826:Microbial Sensitivity Tests; D020102:Mycobacterium smegmatis / Q000187:drug effects / Q000201:enzymology*; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000201:enzymology*; D011161:Porifera; D013329:Structure-Activity Relationship
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D001685:Biological Factors; D004791:Enzyme Inhibitors; D000581:Amidohydrolases; C413523:mycothiol S-conjugate amidase