The single cellular green microalga Botryococcus braunii, race B possesses three distinct 1-deoxy-D-xylulose 5-phosphate synthases.
Green algae exclusively use the methylerythritol 4-phosphate (MEP) pathway for the biosynthesis of isoprenoids. The first enzyme of this pathway is 1-deoxy-D-xylulose 5-phosphate synthase (DXS, EC 2.2.1.7). Green algae have been thought to possess only a single DXS, in contrast to land plants, which have at least two isoforms that serve different roles in metabolism. The green microalga Botryococcus braunii has an extraordinary isoprenoid metabolism, as it produces large amounts of triterpene hydrocarbons. Here, we did cDNA cloning of DXSs from B. braunii and examined enzyme activities of the heterologously expressed proteins. Three distinct DXS isoforms were identified, all of which were functional and had similar kinetic properties, whereas the temperature dependence of enzyme activity showed considerable differences. Transcription of the genes was examined by real time quantitative RT-PCR. The three DXS genes were simultaneously expressed, and the expression levels were highest on day six after subculturing. B. braunii is the first green microalga demonstrated to have multiple DXS isoforms like land plants. This difference to other microalgae seems to mirror its special needs for extensive triterpene production by increasing the metabolic flow through the MEP pathway.
Department of Aquatic Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo, Tokyo 113-8657, Japan.
Daisuke
D
Matsushima
Holger
H
Jenke-Kodama
Yohei
Y
Sato
Yusuke
Y
Fukunaga
Koremitsu
K
Sumimoto
Tomohisa
T
Kuzuyama
Shigeki
S
Matsunaga
Shigeru
S
Okada
D000595:Amino Acid Sequence; D000460:Chlorophyta / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D015723:Gene Library; D007700:Kinetics; D058086:Microalgae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D018515:Plant Leaves / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020033:Protein Isoforms; D011994:Recombinant Proteins; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013696:Temperature; D013729:Terpenes / Q000378:metabolism*; D014166:Transferases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism
D018076:DNA, Complementary; D010940:Plant Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D013729:Terpenes; D014166:Transferases; C109461:deoxyxylulose-5-phosphate synthase