Lipoamino-acids from Bacillus megaterium

Abstract

IT has recently been reported by Macfarlane¹ that lipoamino-acids are probably of general occurrence in bacteria, and that they may easily be isolated in good yield if a suitable extraction procedure is selected. It was further shown¹ that these lipoamino-acids could be characterized with reasonable certainty as O-amino-acid esters of phosphatidyl-glycerol. We now report that some of the lipoamino-acid complexes obtainable from Bacillus megaterium² appear to have this same structure. The phosphorus-containing fraction¹ of Hunter and Goodsall² was dissolved in ether and shaken at 20° for 30 min with an equal volume of N/15 sodium hydroxide (cf. Macfarlane¹). This procedure reduced the nitrogen content of the ether phase from 2.5 per cent to less than 0.1 per cent. At the same time, the lipid became oxidizable by periodic acid with the formation of formaldehyde. Using 0.04 M periodic acid in chloroform–95 per cent acetic acid, 569 µg of the original lipoamino-acid complex yielded 0.69 µmole of formaldehyde after the alkaline treatment (estimated by chromotropic acid; calculation for the O-leucylester of pentadecanoylpalmitylglycerylphosphorylglycerol = 0.71 µmole). After complete hydrolysis of the lipoamino-acid complex, the only organic compound detectable apart from amino- and carboxylic-acids was glycerol, which was isolated as the crystalline tribenzoate.