Analysis of neutral lipid biosynthesis in Streptomyces avermitilis MA-4680 and characterization of an acyltransferase involved herein.
The physiology of lipid production in Streptomyces avermitilis MA-4680 with regard to the fatty acid composition of the accumulated lipids and their cellular distribution was analyzed. Cells were able to accumulate about ten to 30 lipid granules with diameters between 100 and 500 nm filling about 70-80% of the cell cytoplasm. Gas chromatography/mass spectrometry analyses of total cellular lipids and from isolated triacylglycerols (TAG) confirmed a similar fatty acid composition with a large portion of iso- and anteiso-methyl-branched fatty acids. De novo biosynthesis of wax esters (WE) appeared only during cocultivation on glucose and hexadecanol as carbon source. Homology alignments with the wax ester synthase/acyl-CoA:diacylglycerol acyltransferase (WS/DGAT; AtfA) from Acinetobacter baylyi strain ADP1 yielded one open reading frame in the genome databases of S. avermitilis MA-4680 referred to as SAV7256 with 25.3% homology. The highly conserved HHAxxDG active site motif found in AtfA, which is present in SAV7256, as well as the similar hydrophobicity profiles of AtfA and SAV7256 indicate a similar structure and function of both proteins. High acyl-CoA:diacylglycerol acyltransferase activity (DGAT; 143 pmol (mg min)(-1)) but low wax ester synthase activity (WS; 1.3 pmol (mg min)(-1)) were detected in crude extracts of S. avermitilis, which were consistent with the high TAG and negligible WE content of the cells. This indicates that TAG accumulation in S. avermitilis MA-4680 is mediated by the classical acyl-CoA-dependent DGAT pathway. Heterologous expression experiments in recombinant Escherichia coli BL21(DE3) demonstrated both WS and DGAT enzyme activity of SAV7256. Furthermore, substrate specificities of the acyltransferase SAV7256 will be discussed.
Kaddor
Chlud
C
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany.
Biermann
Karolin
K
Kalscheuer
Rainer
R
Steinbüchel
Alexander
A
D000217:Acyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D008055:Lipids / Q000096:biosynthesis* / Q000737:chemistry; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013302:Streptomyces / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D013379:Substrate Specificity
D001426:Bacterial Proteins; D008055:Lipids; D000217:Acyltransferases