Primary structure of a new phosphocholine-containing glycoglycerolipid of Mycoplasma fermentans

The chemical structure of a novel phosphocholine-containing glycoglycerolipid, the major polar lipid in the cell membrane of Mycoplasma fermentans PG18, was investigated by chemical analyses, gas-liquid chromatography-mass spectrometry, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, as well as one- and two- dimensional homo- and heteronuclear NMR spectroscopy and identified as 6'-O- (3''-phosphocholine-2''-amino-1''-phospho-1'',3''-propanediol)-α-D- glucopyranosyl-(1'→3)-1,2-diacylglycerol (MfGL-II). Palmitate (16:0) and stearate (18:0), in a 3.6:1 molar ratio, constitute the major fatty acids present. MALDI-TOF mass spectrometry revealed two major pseudomolecular ions at m/z 1049.5 [M(I) + H]⁺ and 1077.3 [M(II) + H]⁺ representing a dipalmitoyl as the major component and a palmitoyl-stearoyl structure as a minor component. This is the first report of 2-amino-1,3-propanediol-1,3- bisphosphate present in a natural product. This glycoglycerolipid is the second phosphocholine-containing glycoglycerolipid found in M. fermentans.