The alternative pathway C20 Delta8-desaturase from the non-photosynthetic organism Acanthamoeba castellanii is an atypical cytochrome b5-fusion desaturase.
A cDNA encoding a C20 Delta8-desaturase was isolated from the free-living soil amoeba, Acanthamoeba castellanii and functionally characterised by heterologous expression. The open reading frame of the A. castellanii C20 Delta8-desaturase showed similarity to other microsomal front-end desaturases, but the N-terminal domain contained a variant form of the conserved heme-binding motif in which H-P-G-G is replaced by H-P-A-G. Co-expression of the A. castellani Delta8-desaturase with the Isochrysis galbana Delta9-elongase in transgenic Arabidopsis plants confirmed the activity observed in yeast and its role in the alternative pathway for C20 polyunsaturated fatty acid synthesis. Acyl-CoA profiles of these transgenic plants revealed an unexpected accumulation of C20 fatty acids in the acyl-CoA pool. This is the first report of an alternative pathway C20 Delta8-desaturase from a non-photosynthetic organism, and also the first report of a front-end desaturase lacking the canonical cytochrome b5 domain.
Sayanova
Olga
O
Rothamsted Research, Harpenden, Herts AL5 2JQ, UK.
Haslam
Richard
R
Qi
Baoxiu
B
Lazarus
Colin M
CM
Napier
Johnathan A
JA
D048248:Acanthamoeba castellanii / Q000201:enzymology*; D000214:Acyl Coenzyme A / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology; D015786:Cytochromes b5 / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000737:chemistry / Q000378:metabolism*; D015870:Gene Expression; D008969:Molecular Sequence Data; D010788:Photosynthesis; D010802:Phylogeny; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology
D000214:Acyl Coenzyme A; D011993:Recombinant Fusion Proteins; D015786:Cytochromes b5; D044943:Fatty Acid Desaturases; C119257:delta-8 fatty acid desaturase