Several members of the Actinomycetales, including the medically important mycobacteria, produce 1-D-myo-inosityl-2-(N-acetyl-l-cysteinyl)amino-2-deoxy-α-d-glucopyranoside (trivial name mycothiol) as their principal low-molecular-mass thiol. The pseudo-disaccharide component of mycothiol, 1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside (α-D-GI), was synthesized by ligation of 1-D,l-2,3,4,5,6-penta-O-acetyl-myo-inositol to 3,4,6-tri-O-acetyl-2-deoxy-2-(2,4-dinitrophenylamino)-α-D-glu-copyranosyl bromide to give, in the first instance, an isomeric mixture of α- and β-linked pseudo-disaccharides. The α-coupled d,D and D,l isomers, α-d-GI and α-l-GI respectively, were purified from the mixture by TLC, followed by removal of the protecting groups. A cell-free extract of Mycobacterium smegmatis catalysed the ligation of cysteine, acetate and α-D-GI in the presence of ATP and Mg2+ to form mycothiol, as judged by HPLC. When no acetate was added to the incubation mixture, an additional thiol accumulated. In the presence of [14C]acetate no radiolabel was recovered in this species, but only in mycothiol. The additional thiol was isolated as the bimane derivative, and 1H and 1H–1H COSY NMR spectra confirmed its identity as desacetylmycothiol. A more complete conversion of desacetylmycothiol into mycothiol was achieved in the presence of acetyl-S-CoA. These results indicate that the biosynthesis of mycothiol proceeds by the sequential addition of cysteine and acetate to α-D-GI. The inositol moiety appears to be an important determinant of specificity, since α-L-GI was poorly utilized.
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August 1997
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Research Article|
August 01 1997
Biosynthesis of mycothiol: elucidation of the sequence of steps in Mycobacterium smegmatis
Claus BORNEMANN;
Claus BORNEMANN
*Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, South Africa
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M. Anwar JARDINE;
M. Anwar JARDINE
*Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, South Africa
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Hendrik S. C. SPIES;
Hendrik S. C. SPIES
†NMR Laboratory, University of Stellenbosch, Matieland 7602, South Africa
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Daniel J. STEENKAMP
Daniel J. STEENKAMP
‡
*Department of Chemical Pathology, University of Cape Town Medical School, Observatory 7925, South Africa
‡To whom correspondence should be adressed.
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Publisher: Portland Press Ltd
Received:
December 02 1996
Revision Received:
March 10 1997
Accepted:
March 18 1997
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1997
1997
Biochem J (1997) 325 (3): 623–629.
Article history
Received:
December 02 1996
Revision Received:
March 10 1997
Accepted:
March 18 1997
Citation
Claus BORNEMANN, M. Anwar JARDINE, Hendrik S. C. SPIES, Daniel J. STEENKAMP; Biosynthesis of mycothiol: elucidation of the sequence of steps in Mycobacterium smegmatis. Biochem J 1 August 1997; 325 (3): 623–629. doi: https://doi.org/10.1042/bj3250623
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