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)-alpha-D-glucopyranosyl-(1'-->3)-1,2-diacyl-glycerol (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 [MI + H]+ and 1077.3 [MII + 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.