title: Sterol biosynthesis by a prokaryote: first in vitro identification of the genes encoding squalene epoxidase and lanosterol synthase from Methylococcus capsulatus.
abstract: Sterol biosynthesis by prokaryotic organisms is very rare. Squalene epoxidase and lanosterol synthase are prerequisite to cyclic sterol biosynthesis. These two enzymes, from the methanotrophic bacterium Methylococcus capsulatus, were functionally expressed in Escherichia coli. Structural analyses of the enzymatic products indicated that the reactions proceeded in a complete regio- and stereospecific fashion to afford (3S)-2,3-oxidosqualene from squalene and lanosterol from (3S)-2,3-oxidosqualene, in full accordance with those of eukaryotes. However, our result obtained with the putative lanosterol synthase was inconsistent with a previous report that the prokaryote accepts both (3R)- and (3S)-2,3-oxidosqualenes to afford 3-epi-lanosterol and lanosterol, respectively. This is the first report demonstrating the existence of the genes encoding squalene epoxidase and lanosterol synthase in prokaryotes by establishing the enzyme activities. The evolutionary aspect of prokaryotic squalene epoxidase and lanosterol synthase is discussed.
authors.affiliation: Graduate School of Science and Technology, Niigata University, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Nakano
authors.forename: Akihiro
authors.initials: A
authors.lastname: Motegi
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Sato
authors.forename: Masayuki
authors.initials: M
authors.lastname: Onodera
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Hoshino
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002474:Cell-Free System; D002849:Chromatography, Gas; D003001:Cloning, Molecular; D017124:Conserved Sequence; D004926:Escherichia coli / Q000737:chemistry; D005798:Genes, Bacterial; D066298:In Vitro Techniques; D019751:Intramolecular Transferases / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D020619:Methylococcus capsulatus / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010957:Plasmids; D011387:Prokaryotic Cells / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D050603:Squalene Monooxygenase / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D013237:Stereoisomerism
chemical_list: D050603:Squalene Monooxygenase; D019751:Intramolecular Transferases; C021924:lanosterol synthase