The role of KasA and KasB in the biosynthesis of meromycolic acids and isoniazid resistance in Mycobacterium tuberculosis
| Autor: | C E Barry rd, Richard A. Slayden |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Microbiology (medical)
Operon Mycobacterium smegmatis Immunology Mutant Thiophenes Biology Microbiology Substrate Specificity Mycobacterium tuberculosis chemistry.chemical_compound Biosynthesis 3-Oxoacyl-(Acyl-Carrier-Protein) Synthase Drug Resistance Bacterial Isoniazid medicine Antibiotics Antitubercular chemistry.chemical_classification Cell-Free System ATP synthase biology.organism_classification Triclosan In vitro Culture Media Infectious Diseases Enzyme Mycolic Acids chemistry Biochemistry Mutation biology.protein Fatty Acid Synthases medicine.drug |
| Zdroj: | Tuberculosis. 82:149-160 |
| ISSN: | 1472-9792 |
| DOI: | 10.1054/tube.2002.0333 |
| Popis: | Mycobacterium tuberculosis has two discrete β-ketoacyl synthases encoded by kasA and kasB that are located in tandem within a five-gene operon that has been implicated in isoniazid-sensitivity and mycolic acid synthesis. We have developed an in vitro meromycolic acid synthase assay to elucidate the anabolic role of these enzymes. Overproduction of KasA and KasB individually and together in M. smegmatis enabled cell-free incorporation of [ 14 C]malonyl-CoA into lipids whose chain length was dependent upon the M. tuberculosis elongating enzyme used. KasA specifically elongated palmitoyl-CoA to monounsaturated fatty acids that averaged 40 carbons in length. KasB hyperproduction in the presence of KasA produced longer chain multiunsaturated hydrocarbons averaging 54 carbons in length. These products comigrated with a synthetic standard of meromycolic acid and their production was sensitive to isoniazid, thiolactomycin, and triclosan. KasA mutations associated with isoniazid resistance produced an enzyme that had a diminished overall catalytic activity but conferred enhanced resistance to isoniazid. In vivo analysis confirmed that overexpression of each of the four mutant KasAs enhanced isoniazid resistance when compared to overexpression of wild-type KasA. These results suggest discrete anabolic roles for both KasA and KasB in mycolic acid synthesis and substantiate the involvement of KasA mutations in isoniazid resistance. |
| Databáze: | OpenAIRE |
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