Phylogenomic Investigation of Phospholipid Synthesis in Archaea
Biosynthesis pathways of phospholipid components in archaea. Abbreviations for the archaeal mevalonate (MVA) pathway: AACT, acetoacetyl-CoA thiolase; HMGS, 3-hydroxy-3-methylglutaryl-CoA synthase; HMGR, 3-hydroxy-3-methylglutaryl-CoA reductase; MVK, mevalonate kinase; IPK, isopentenyl phosphate kinase; IDI2, isopentenyl diphosphate isomerase type II. GHMP, galactokinase-homoserine kinase-mevalonate kinase-phosphomevalonate kinase; IPPS, isoprenyl diphosphate synthases (asterisks indicate enzymes shared with the eukaryotic MVA pathway). Abbreviations for the hypothetical archaeal fatty acid (FA) synthesis pathway: ACC, acetyl-CoA carboxylase; PCC, propionyl-CoA carboxylase; KR-PhaB, beta-ketoacyl reductase; DH-MaoC/PhaJ, beta-hydroxyacyl dehydratase; ER, enoyl reductase; SDR, short-chain dehydrogenases/reductases. Abbreviations for the sn-glycerol-1-phosphate synthesis pathway: G1PDH, glycerol-1-phosphate dehydrogenase; DHQS, 3-dehydroquinate synthase; GDH, glycerol dehydrogenase; ADH, alcohol dehydrogenase. Abbreviations for the phospholipid assembly pathway: GGGPS, (S)-3-O-geranylgeranylglyceryl phosphate synthase; DGGGPS, (S)-2,3-di-O-geranylgeranylglyceryl phosphate synthase; GGR, geranylgeranyl reductase; CDSA, CDP diglyceride synthetase. (#) points to the ability of GGRs to reduce isoprenoids at different steps in the biosynthesis pathway. Names between parentheses indicate the family or superfamily to which belong the archaeal enzymes postulated to carry out particular functions on the basis of phylogenomic analyses.