© 2002 Heron Publishing—Victoria, Canada
Structural analysis by reductive cleavage with LiAlH4 of an allyl ether choline-phospholipid, archaetidylcholine, from the hyperthermophilic methanoarchaeon Methanopyrus kandleri
Masateru Nishihara (1, 2), Hiroyuki Morii (1), Koji Matsuno (3), Mami Ohga (1), Karl O. Stetter (4) and Yosuke Koga (1, 5)
1. Department of Chemistry, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan / 2. Deceased August 23, 2001 / 3. Instrumental Analytical Laboratory, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan / 4. Lehrstuhl für Mikrobiologie, Universität Regensburg, Regensburg D-93053, Germany / 5. Author to whom correspondence should be addresssed ([email protected]) / Received January 10, 2002; accepted April 23, 2002; published online June 18, 2002
A choline-containing phospholipid (PL-4) in Methanopyrus kandleri cells was identified as archaetidylcholine, which has been described by Sprott et al. (1997). The PL-4 consisted of a variety of molecular species differing in hydrocarbon composition. Most of the PL-4 was acid-labile because of its allyl ether bond. The identity of PL-4 was confirmed by thin-layer chromatography (TLC) followed by positive staining with Dragendorff-reagent and fast-atom bombardment–mass spectrometry. A new method of LiAlH4 hydrogenolysis was developed to cleave allyl ether bonds and recover the corresponding hydrocarbons. We confirmed the validity of the LiAlH4 method in a study of the model compound synthetic unsaturated archaetidic acid (2,3-di-O-geranylgeranyl-sn-glycerol-1-phosphate). Saturated ether bonds were not cleaved by the LiAlH4 method. The hydrocarbons formed following LiAlH4 hydrogenolysis of PL-4 were identified by gas–liquid chromatography and mass spectrometry. Four kinds of hydrocarbons with one to four double bonds were detected: 47% of the hydrocarbons had four double bonds; 11% had three double bonds; 14% had two double bonds; 7% had one double bond; and 6% were saturated species. The molecular species composition of PL-4 was also estimated based on acid lability: 77% of the molecular species had two acid-labile hydrocarbons; 11% had one acid-labile and one acid-stable hydrocarbon; and 11% had two acid-stable hydrocarbons. To our knowledge, this is the first report of a specific chemical degradation method for the structural analysis of allyl ether phospholipid in archaea.
Keywords: acid-labile phospholipid, LiAlH4 hydrogenolysis, molecular species composition, unsaturated isoprenoid.
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