Mycobacterium smegmatis fatty acid synthetase. Polysaccharide stimulation of the rate-limiting step.

Banis, R. J.; Peterson, D O; Bloch, Konrad E.

doi:10.1016/s0021-9258(17)40085-8

Cited by 24 publications

(7 citation statements)

References 7 publications

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“…It is well established that FAS I exhibits a bimodal product behaviour and that the two dominant products are C 16-18 -CoA and C 24 -CoA in M. smegmatis. However, it has also been demonstrated that the overall rate of FA biosynthesis as well as the product distribution of this enzyme becomes affected by endogenous polysaccharides or by interactions of the mycobacterial FAS I with other FA processing enzymes like the FAS II system [25,[36][37][38]. Thus, the unexpected accumulation of long-chain acyl-CoAs, when FAS I was downregulated, could be the result of a biochemical change in the bimodal behaviour of the FAS I system when the cells become stressed by the deficiency of de novo FA biosynthesis.…”

Section: Discussionmentioning

confidence: 99%

A conditional mutant of the fatty acid synthase unveils unexpected cross talks in mycobacterial lipid metabolism

et al. 2017

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Unlike most bacteria, mycobacteria rely on the multi-domain enzyme eukaryote-like fatty acid synthase I (FAS I) to make fatty acids de novo. These metabolites are precursors of the biosynthesis of most of the lipids present both in the complex mycobacteria cell wall and in the storage lipids inside the cell. In order to study the role of the type I FAS system in Mycobacterium lipid metabolism in vivo, we constructed a conditional mutant in the fas-acpS operon of Mycobacterium smegmatis and analysed in detail the impact of reduced de novo fatty acid biosynthesis on the global architecture of the cell envelope. As expected, the mutant exhibited growth defect in the non-permissive condition that correlated well with the lower expression of fas-acpS and the concomitant reduction of FAS I, confirming that FAS I is essential for survival. The reduction observed in FAS I provoked an accumulation of its substrates, acetyl-CoA and malonyl-CoA, and a strong reduction of C12 to C18 acyl-CoAs, but not of long-chain acyl-CoAs (C19 to C24). The most intriguing result was the ability of the mutant to keep synthesizing mycolic acids when fatty acid biosynthesis was impaired. A detailed comparative lipidomic analysis showed that although reduced FAS I levels had a strong impact on fatty acid and phospholipid biosynthesis, mycolic acids were still being synthesized in the mutant, although with a different relative species distribution. However, when triacylglycerol degradation was inhibited, mycolic acid biosynthesis was significantly reduced, suggesting that storage lipids could be an intracellular reservoir of fatty acids for the biosynthesis of complex lipids in mycobacteria. Understanding the interaction between FAS I and the metabolic pathways that rely on FAS I products is a key step to better understand how lipid homeostasis is regulated in this microorganism and how this regulation could play a role during infection in pathogenic mycobacteria.

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Section: Discussionmentioning

confidence: 99%

A conditional mutant of the fatty acid synthase unveils unexpected cross talks in mycobacterial lipid metabolism

et al. 2017

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“…The vast majority of these studies have been performed in vitro in Konrad Bloch's laboratory. 23,24,26,[45][46][47][48] These extensive studies with cell-free assays disclosed the ability of PMPSs to form stable 1 : 1 ratio complexes with fatty acyl chains and acyl-CoAs, and to sequester the newly synthesized products of fatty acid synthase I (FAS-I), 23 which elicits a unique regulatory role on the activity rate of the mycobacterial FAS-I complex. [23][24][25] PMPSs preferentially interact with fatty acids with chain length ranging from C 16 -C 22 , while the interaction with immediately shorter or longer fatty-acyl chains has a significantly lower affinity and never reaches the 1 : 1 molar ratio.…”

Section: Mglps Chemical Nature and Structurementioning

confidence: 99%

“…23 By facilitating the diffusion of FAS-I end products, PMPSs were shown to stimulate the activity of this enzyme complex by mitigating product inhibition and allowing a continuous synthesis of acyl-CoAs. 23,25,45,47 MGLPs shift the length pattern of the synthesized chains from C 20 -C 24 to C 14 -C 18 that leads to a dramatic change in the proportion of C 14 -C 18 chains in the presence of the polysaccharides, with an increase from less than 20% to more than 80% of the total synthesized chains. 45 The polysaccharides markedly decrease the K m of the FAS-I for acyl-CoA substrates, enabling the synthesis to continue at low substrate concentrations, and allowing a higher enzyme turnover by promoting faster chain release and terminating the elongation.…”

Section: Mglps Chemical Nature and Structurementioning

confidence: 99%

“…23,25,45,47 MGLPs shift the length pattern of the synthesized chains from C 20 -C 24 to C 14 -C 18 that leads to a dramatic change in the proportion of C 14 -C 18 chains in the presence of the polysaccharides, with an increase from less than 20% to more than 80% of the total synthesized chains. 45 The polysaccharides markedly decrease the K m of the FAS-I for acyl-CoA substrates, enabling the synthesis to continue at low substrate concentrations, and allowing a higher enzyme turnover by promoting faster chain release and terminating the elongation. 23,26,45,47,49 Since no stimulatory effect of the MGLPs was observed for each of the individual reaction steps catalyzed by FAS-I, a possible justification for the observed decrease in the K m for the acyl-CoAs is that the polysaccharides' acyl groups may themselves serve as acceptors of long-chain fatty acids.…”

Section: Mglps Chemical Nature and Structurementioning

confidence: 99%

“…45 The polysaccharides markedly decrease the K m of the FAS-I for acyl-CoA substrates, enabling the synthesis to continue at low substrate concentrations, and allowing a higher enzyme turnover by promoting faster chain release and terminating the elongation. 23,26,45,47,49 Since no stimulatory effect of the MGLPs was observed for each of the individual reaction steps catalyzed by FAS-I, a possible justification for the observed decrease in the K m for the acyl-CoAs is that the polysaccharides' acyl groups may themselves serve as acceptors of long-chain fatty acids. 26 PMPSs reach intracellular concentrations of about 1 mM in M. smegmatis while the concentration of long-chain acyl-CoAs is about 0.3 mM.…”

Section: Mglps Chemical Nature and Structurementioning

confidence: 99%

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Biosynthesis of mycobacterial methylglucose lipopolysaccharides

et al. 2012

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Mycobacterial pathogenesis is closely associated with a unique cell envelope rich in complex carbohydrates and unique lipids, among which are the mycolic acids. Mycobacteria also synthesize unique intracellular polymethylated polysaccharides (PMPSs), namely methylglucose lipopolysaccharides (MGLPs), which are acylated with short-chain fatty acids, and methylmannose polysaccharides (MMPs). Since PMPSs modulate the synthesis of long-chain fatty acids in vitro, the possibility of a similar role in vivo and the regulation of mycolic acids assembly have been anticipated. Unlike MGLPs, MMPs have been identified in M. smegmatis and other fast-growing mycobacteria but not in M. tuberculosis, implying an essential role for MGLPs in this pathogen and turning the biosynthetic enzymes into attractive drug targets. The genome of M. tuberculosis was decoded 14 years ago but only recently has the identity of the genes involved in MGLPs biosynthesis been investigated. Two gene clusters (Rv1208-Rv1213 and Rv3030-Rv3037c) containing a few genes considered to be essential for M. tuberculosis growth, have initially been proposed to coordinate MGLPs biosynthesis. Among these genes, only the product of Rv1208 for the first step in the MGLPs pathway has, so far, been crystallized and its three-dimensional structure been determined. However, recent results indicate that at least three additional clusters may be involved in this pathway. The functional assignment of authentic roles to some of these M. tuberculosis H37Rv genes sheds new light on the intricacy of MGLPs biogenesis and renewed interest on their biological role.

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The Publications of Konrad Bloch

2002

Biochemical and Biophysical Research Communications

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Mycobacterium smegmatis fatty acid synthetase. Polysaccharide stimulation of the rate-limiting step.

Cited by 24 publications

References 7 publications

A conditional mutant of the fatty acid synthase unveils unexpected cross talks in mycobacterial lipid metabolism

A conditional mutant of the fatty acid synthase unveils unexpected cross talks in mycobacterial lipid metabolism

Biosynthesis of mycobacterial methylglucose lipopolysaccharides

The Publications of Konrad Bloch

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