Role of the methylcitrate cycle in Mycobacterium tuberculosis metabolism, intracellular growth, and virulence
Summary Growth of bacteria and fungi on fatty acid substrates requires the catabolic β‐oxidation cycle and the anaplerotic glyoxylate cycle. Propionyl‐CoA generated by β‐oxidation of odd‐chain fatty acids is metabolized via the methylcitrate cycle. Mycobacterium tuberculosis possesses homologues of...
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Published in | Molecular microbiology Vol. 60; no. 5; pp. 1109 - 1122 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Oxford, UK
Blackwell Publishing Ltd
01.06.2006
Blackwell Science |
Subjects | |
Online Access | Get full text |
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Summary: | Summary
Growth of bacteria and fungi on fatty acid substrates requires the catabolic β‐oxidation cycle and the anaplerotic glyoxylate cycle. Propionyl‐CoA generated by β‐oxidation of odd‐chain fatty acids is metabolized via the methylcitrate cycle. Mycobacterium tuberculosis possesses homologues of methylcitrate synthase (MCS) and methylcitrate dehydratase (MCD) but not 2‐methylisocitrate lyase (MCL). Although MCLs share limited homology with isocitrate lyases (ICLs) of the glyoxylate cycle, these enzymes are thought to be functionally non‐overlapping. Previously we reported that the M. tuberculosis ICL isoforms 1 and 2 are jointly required for growth on fatty acids, in macrophages, and in mice. ICL‐deficient bacteria could not grow on propionate, suggesting that in M. tuberculosis ICL1 and ICL2 might function as ICLs in the glyoxylate cycle and as MCLs in the methylcitrate cycle. Here we provide biochemical and genetic evidence supporting this interpretation. The role of the methylcitrate cycle in M. tuberculosis metabolism was further evaluated by constructing a mutant strain in which prpC (encoding MCS) and prpD (encoding MCD) were deleted. The ΔprpDC strain could not grow on propionate media in vitro or in murine bone marrow‐derived macrophages infected ex vivo; growth under these conditions was restored by complementation with a plasmid containing prpDC. Paradoxically, bacterial growth and persistence, and tissue pathology, were indistinguishable in mice infected with wild‐type or ΔprpDC bacteria. |
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Bibliography: | These authors contributed equally to this work. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0950-382X 1365-2958 |
DOI: | 10.1111/j.1365-2958.2006.05155.x |