Glycosides of Peptidolipids Isolated from Rhodococcus erythropolis

Glycosides of Peptidolipids Isolated from Rhodococcus erythropolis 

Rhodococcus erythropolis produces a complex mixture of peptidolipids which can be separated by chromatography into seven fractions. The three most polar ones contained glycine, L-leucine, D-a//oisoleucine, L-threonine, L-serine, L-homoserine and D-alanine in the molar ratio 3 3 2 2 2 1 1. In two of the peptidolipids glucose was bound to the hydroxyl of a serine residue and in the third, the most strongly adsorbed, glucose was bound to the hydroxyl group of a threonine residue. All these polar compounds contained one mole of a normal-chain fatty acid and one mole of a mycolic acid residue (74). 

By countercurrent distribution, the main component was isolated and designated as herbicolin A. It was accompanied by a minor component, herbicolin B. Both compounds had the same amino acid and fatty acid composition and differed from each other in the presence of d-glucose which was only found in herbicolin A. 

Herbicolin A was labile in acidic and basic media and was inactivated by chromatography on silica gel. An intense MH peak was observed in the FAB and FD mass spectra at m/z 1300. It was shifted to m/z 1302 by hydrogenation and to m/z 1318 by mild treatment with alkali. 

In the mixture of amino acids obtained by hydrolysis three different forms of threonine were found, L-threonine, D-a//othreonine and N-methyl-L-a//othreonine. Their stereochemistry was elucidated by gas chromatography of the derivatives obtained by esterification with (+ )-3-methyl-2-butanol and trimethylsilylation. Synthetic compounds were used for comparison. 

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