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Octanoylation of early intermediates of mycobacterial methylglucose lipopolysaccharides.

Maranha A, Moynihan PJ, Miranda V, Correia Lourenço E, Nunes-Costa D, Fraga JS, José Barbosa Pereira P, Macedo-Ribeiro S, Ventura MR, Clarke AJ, Empadinhas N - Sci Rep (2015)

Bottom Line: In addition to the partial esterification of glucose or methylglucose units with short-chain fatty acids, octanoate was invariably detected on the MGLP reducing end.These observations raise important new questions about the MGLP reducing end architecture and about subsequent biosynthetic steps.Functional characterization of this unique octanoyltransferase, whose gene has been proposed to be essential for M. tuberculosis growth, adds new insights into a vital mycobacterial pathway, which may inspire new drug discovery strategies.

View Article: PubMed Central - PubMed

Affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal.

ABSTRACT
Mycobacteria synthesize unique intracellular methylglucose lipopolysaccharides (MGLP) proposed to modulate fatty acid metabolism. In addition to the partial esterification of glucose or methylglucose units with short-chain fatty acids, octanoate was invariably detected on the MGLP reducing end. We have identified a novel sugar octanoyltransferase (OctT) that efficiently transfers octanoate to glucosylglycerate (GG) and diglucosylglycerate (DGG), the earliest intermediates in MGLP biosynthesis. Enzymatic studies, synthetic chemistry, NMR spectroscopy and mass spectrometry approaches suggest that, in contrast to the prevailing consensus, octanoate is not esterified to the primary hydroxyl group of glycerate but instead to the C6 OH of the second glucose in DGG. These observations raise important new questions about the MGLP reducing end architecture and about subsequent biosynthetic steps. Functional characterization of this unique octanoyltransferase, whose gene has been proposed to be essential for M. tuberculosis growth, adds new insights into a vital mycobacterial pathway, which may inspire new drug discovery strategies.

No MeSH data available.


Related in: MedlinePlus

Early steps of the proposed pathway for MGLP biosynthesis.Newly identified octanoyltransferase (OctT) is highlighted red. The dashed line indicates a hypothetical regulatory role of OctT. Experimentally validated functions are shaded blue. Open boxes represent unknown functions or those lacking biochemical confirmation. R groups (red) on the structure indicate acyl chains (acetate, propionate, isobutyrate or succinate) and methyl groups are in green. 3-PGA, d-3-phosphoglyceric acid. GpgS, glucosyl-3-phosphoglycerate synthase21; GpgP, glucosyl-3-phosphoglycerate phosphatase23; DggS, putative diglucosylglycerate synthase13 GgH, glucosylglycerate hydrolase (detected in rapidly-growing mycobacteria)24.
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f7: Early steps of the proposed pathway for MGLP biosynthesis.Newly identified octanoyltransferase (OctT) is highlighted red. The dashed line indicates a hypothetical regulatory role of OctT. Experimentally validated functions are shaded blue. Open boxes represent unknown functions or those lacking biochemical confirmation. R groups (red) on the structure indicate acyl chains (acetate, propionate, isobutyrate or succinate) and methyl groups are in green. 3-PGA, d-3-phosphoglyceric acid. GpgS, glucosyl-3-phosphoglycerate synthase21; GpgP, glucosyl-3-phosphoglycerate phosphatase23; DggS, putative diglucosylglycerate synthase13 GgH, glucosylglycerate hydrolase (detected in rapidly-growing mycobacteria)24.

Mentions: In this study, we identified a novel mycobacterial acyltransferase that efficiently transfers octanoate to the sugar derivatives glucosylglycerate (GG) and diglucosylglycerate (DGG), the two earliest intermediates in methylglucose lipopolysaccharide (MGLP) biosynthesis20 forming its reducing end structure, reported to be octanoylated in the glycerate moiety1415. Since our preliminary MS results indicated that OctT did not transfer octanoate to the primary hydroxyl group of glycerate4, we deemed essential to perform an exhaustive characterization of the product and found that octanoate is not transferred to glycerate as described for preparations obtained from M. phlei14, but instead to the C6 OH of the second glucose of DGG (Figs 3 and 7).


Octanoylation of early intermediates of mycobacterial methylglucose lipopolysaccharides.

Maranha A, Moynihan PJ, Miranda V, Correia Lourenço E, Nunes-Costa D, Fraga JS, José Barbosa Pereira P, Macedo-Ribeiro S, Ventura MR, Clarke AJ, Empadinhas N - Sci Rep (2015)

Early steps of the proposed pathway for MGLP biosynthesis.Newly identified octanoyltransferase (OctT) is highlighted red. The dashed line indicates a hypothetical regulatory role of OctT. Experimentally validated functions are shaded blue. Open boxes represent unknown functions or those lacking biochemical confirmation. R groups (red) on the structure indicate acyl chains (acetate, propionate, isobutyrate or succinate) and methyl groups are in green. 3-PGA, d-3-phosphoglyceric acid. GpgS, glucosyl-3-phosphoglycerate synthase21; GpgP, glucosyl-3-phosphoglycerate phosphatase23; DggS, putative diglucosylglycerate synthase13 GgH, glucosylglycerate hydrolase (detected in rapidly-growing mycobacteria)24.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555173&req=5

f7: Early steps of the proposed pathway for MGLP biosynthesis.Newly identified octanoyltransferase (OctT) is highlighted red. The dashed line indicates a hypothetical regulatory role of OctT. Experimentally validated functions are shaded blue. Open boxes represent unknown functions or those lacking biochemical confirmation. R groups (red) on the structure indicate acyl chains (acetate, propionate, isobutyrate or succinate) and methyl groups are in green. 3-PGA, d-3-phosphoglyceric acid. GpgS, glucosyl-3-phosphoglycerate synthase21; GpgP, glucosyl-3-phosphoglycerate phosphatase23; DggS, putative diglucosylglycerate synthase13 GgH, glucosylglycerate hydrolase (detected in rapidly-growing mycobacteria)24.
Mentions: In this study, we identified a novel mycobacterial acyltransferase that efficiently transfers octanoate to the sugar derivatives glucosylglycerate (GG) and diglucosylglycerate (DGG), the two earliest intermediates in methylglucose lipopolysaccharide (MGLP) biosynthesis20 forming its reducing end structure, reported to be octanoylated in the glycerate moiety1415. Since our preliminary MS results indicated that OctT did not transfer octanoate to the primary hydroxyl group of glycerate4, we deemed essential to perform an exhaustive characterization of the product and found that octanoate is not transferred to glycerate as described for preparations obtained from M. phlei14, but instead to the C6 OH of the second glucose of DGG (Figs 3 and 7).

Bottom Line: In addition to the partial esterification of glucose or methylglucose units with short-chain fatty acids, octanoate was invariably detected on the MGLP reducing end.These observations raise important new questions about the MGLP reducing end architecture and about subsequent biosynthetic steps.Functional characterization of this unique octanoyltransferase, whose gene has been proposed to be essential for M. tuberculosis growth, adds new insights into a vital mycobacterial pathway, which may inspire new drug discovery strategies.

View Article: PubMed Central - PubMed

Affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal.

ABSTRACT
Mycobacteria synthesize unique intracellular methylglucose lipopolysaccharides (MGLP) proposed to modulate fatty acid metabolism. In addition to the partial esterification of glucose or methylglucose units with short-chain fatty acids, octanoate was invariably detected on the MGLP reducing end. We have identified a novel sugar octanoyltransferase (OctT) that efficiently transfers octanoate to glucosylglycerate (GG) and diglucosylglycerate (DGG), the earliest intermediates in MGLP biosynthesis. Enzymatic studies, synthetic chemistry, NMR spectroscopy and mass spectrometry approaches suggest that, in contrast to the prevailing consensus, octanoate is not esterified to the primary hydroxyl group of glycerate but instead to the C6 OH of the second glucose in DGG. These observations raise important new questions about the MGLP reducing end architecture and about subsequent biosynthetic steps. Functional characterization of this unique octanoyltransferase, whose gene has been proposed to be essential for M. tuberculosis growth, adds new insights into a vital mycobacterial pathway, which may inspire new drug discovery strategies.

No MeSH data available.


Related in: MedlinePlus