Article Summary
Archaea, 1:123131
© 2002 Heron PublishingVictoria, Canada
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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 addressed ([email protected])

Received January 10, 2002; accepted April 23, 2002; published online June 18, 2002

Summary
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.