title: Biosynthesis of archaeal membrane lipids: digeranylgeranylglycerophospholipid reductase of the thermoacidophilic archaeon Thermoplasma acidophilum.
abstract: The basic core structure of archaeal membrane lipids is 2,3-di-O-phytanyl-sn-glyceryl phosphate (archaetidic acid), which is formed by the reduction of 2,3-di-O-geranylgeranylglyceryl phosphate. The reductase activity for the key enzyme in membrane lipid biosynthesis, 2,3-digeranylgeranylglycerophospholipid reductase, was detected in a cell free extract of the thermoacidophilic archaeon Thermoplasma acidophilum. The reduction activity was found in the membrane fraction, and FAD and NADH were required for the activity. The reductase was purified from a cell free extract by ultracentrifugation and four chromatographic steps. The purified enzyme showed a single band at ca. 45 kDa on SDS-PAGE, and catalyzed the formation of archaetidic acid from 2,3-di-O-geranylgeranylglyceryl phosphate. Furthermore, the enzyme also catalyzed the reduction of 2,3-di-O-geranylgeranylglyceryl phosphate analogues such as 2,3-di-O-phytyl-sn-glyceryl phosphate, 3-O-(2,3-di-O-phytyl-sn-glycero-phospho)-sn-glycerol and 2,3-di-O-phytyl-sn-glycero-phosphoethanolamine. The N-terminal 20 amino acid sequence of the purified enzyme was determined and was found to be identical to the sequence encoded by the Ta0516m gene of the T. acidophilum genome. The present study clearly demonstrates that 2,3-digeranylgeranylglycerophospholipid reductase is a membrane associated protein and that the hydrogenation of each double bond of 2,3-digeranylgeranylglycerophospholipids is catalyzed by a single enzyme.
authors.affiliation: Department of Chemistry & Materials Science, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8551.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Tadashi
authors.initials: T
authors.lastname: Eguchi
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002384:Catalysis; D004591:Electrophoresis, Polyacrylamide Gel; D050356:Lipid Metabolism; D009682:Magnetic Resonance Spectroscopy; D008563:Membrane Lipids / Q000096:biosynthesis*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D010802:Phylogeny; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013379:Substrate Specificity; D013822:Thermoplasma / Q000201:enzymology* / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D008563:Membrane Lipids; D019883:Alkyl and Aryl Transferases; C083737:phosphoglycerol geranylgeranyltransferase