Control Mechanisms for Fatty Acid Synthesis in Mycobacterium Smegmatis

Bloch, Konrad E.

doi:10.1002/9780470122907.ch1

Cited by 84 publications

(53 citation statements)

References 90 publications

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“…Mycobacteria, unlike most bacteria, have two fatty acid synthases. The eukaryote-like FASI, which is a large multidomain polypeptide containing all enzymatic functions required for de novo fatty acid synthesis, produces in a bimodal fashion saturated fatty acids of palmitate (C 16:0 ) and tetracosanoate (C 24:0 ) or C 26 (6,30). FASII elongates FASI end products to form long-chain fatty acids or meromycolates.…”

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confidence: 99%

Conditional Depletion of KasA, a Key Enzyme of Mycolic Acid Biosynthesis, Leads to Mycobacterial Cell Lysis

et al. 2005

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Inhibition or inactivation of InhA, a fatty acid synthase II (FASII) enzyme, leads to mycobacterial cell lysis. To determine whether inactivation of other enzymes of the mycolic acid-synthesizing FASII complex also leads to lysis, we characterized the essentiality of two ␤-ketoacyl-acyl carrier protein synthases, KasA and KasB, in Mycobacterium smegmatis. Using specialized transduction for allelic exchange, null kasB mutants, but not kasA mutants, could be generated in Mycobacterium smegmatis, suggesting that unlike kasB, kasA is essential. To confirm the essentiality of kasA, and to detail the molecular events that occur following depletion of KasA, we developed CESTET (conditional expression specialized transduction essentiality test), a genetic tool that combines conditional gene expression and specialized transduction. Using CESTET, we were able to generate conditional null inhA and kasA mutants. We studied the effects of depletion of KasA in M. smegmatis using the former strain as a reference. Depletion of either InhA or KasA led to cell lysis, but with different biochemical and morphological events prior to lysis. While InhA depletion led to the induction of an 80-kDa complex containing both KasA and AcpM, the mycobacterial acyl carrier protein, KasA depletion did not induce the same complex. Depletion of either InhA or KasA led to inhibition of ␣ and epoxy mycolate biosynthesis and to accumulation of ␣-mycolates. Furthermore, scanning electron micrographs revealed that KasA depletion resulted in the cell surface having a "crumpled" appearance, in contrast to the blebs observed on InhA depletion. Thus, our studies support the further exploration of KasA as a target for mycobacterial-drug development.The emergence of multidrug-resistant Mycobacterium tuberculosis has been partly responsible for the global spread of tuberculosis (TB) in the past decade (51). There is an urgent need to develop novel drugs that are active against M. tuberculosis. Existing antimycobacterial agents act either by inhibiting growth or by causing cell death. The antituberculosis drug isoniazid (INH) inhibits the biosynthesis of mycolic acids, major components of cell wall lipids, resulting in cell death by lysis (43,49,50). INH inhibits InhA (1, 21, 32), an enoyl-acyl carrier protein (ACP) reductase which is part of the multienzyme fatty acid synthase II complex (FASII) that synthesizes the meromycolate precursors of mycolic acids. Although the structures of mycolic acids have been well characterized, the genetics and enzymology of mycolic acid biosynthesis have only recently begun to be elucidated (1,2,15,20,32,36,37,42,47). Mycobacteria, unlike most bacteria, have two fatty acid synthases. The eukaryote-like FASI, which is a large multidomain polypeptide containing all enzymatic functions required for de novo fatty acid synthesis, produces in a bimodal fashion saturated fatty acids of palmitate (C 16:0 ) and tetracosanoate (C 24:0 ) or C 26 (6,30). FASII elongates FASI end products to form long-chain fatty acids or meromycolates....

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confidence: 99%

Conditional Depletion of KasA, a Key Enzyme of Mycolic Acid Biosynthesis, Leads to Mycobacterial Cell Lysis

et al. 2005

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“…Given the assumed similarity of the intracellular environment of M. smegmatis (used for expression) and M. tuberculosis, we conclude that palmitoyl-CoA or a similar long chain fatty acid derivative is the likely substrate of PKS11 in vivo. Palmitate is expected to be abundant in M. tuberculosis, as it is the primary product of the FAS-I system in mycobacteria (32). Similar to other PKSs, this substrate is then extended by two rounds of condensation with MCoA and MMCoA to form a triketide thioester.…”

Section: Discussionmentioning

confidence: 99%

Crystal Structure of Mycobacterium tuberculosis Polyketide Synthase 11 (PKS11) Reveals Intermediates in the Synthesis of Methyl-branched Alkylpyrones

Gokulan

O’Leary

Russell

et al. 2013

Journal of Biological Chemistry

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Background: Polyketide synthases (PKSs) synthesize complex lipid components of the cell wall in M. tuberculosis. Results: We determined the crystal structure of M. tuberculosis PKS11 and identified its substrate, intermediates, and product. Conclusion: M. tuberculosis PKS11 synthesizes a unique cyclic methyl-branched alkylpyrone. Significance: Our identification of alkylpyrones as the product of this PKS suggests a previously unknown component of the mycobacterial cell wall.

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“…2). Studies on fatty acid synthesis date back to the 1970s when M. smegmatis was shown to contain both type I fatty acid synthetase (FAS-I), involving a large multifunctional polypeptide, and type II fatty acid synthetase (FAS-II), consisting of a series of distinct enzymes [64]. …”

Section: Fatty Acidsmentioning

confidence: 99%

“…Then MtFabH performs a Claisen condensation of malonyl-ACP with acyl-CoA to form -ketoacyl-ACP. A four-step cycle is then initiated [64] in which:…”

Section: Elongation By Fas-iimentioning

confidence: 99%