Publications

• Functional expression of Spirulina-Delta6 desaturase gene in yeast, Saccharomyces cerevisiae.

  Kurdrid P., Subudhi S., Hongsthong A., Ruengjitchatchawalya M., Tanticharoen M.

  Spirulina-acyl-lipid desaturases are membrane-bound enzymes found in thylakoid and plasma membranes. These enzymes carry out the fatty acid desaturation process of Spirulina to yield gamma-linolenic acid (GLA) as the final desaturation product. In this study, Spirulina-Delta(6) desaturase encoded ... >> More

  Spirulina-acyl-lipid desaturases are membrane-bound enzymes found in thylakoid and plasma membranes. These enzymes carry out the fatty acid desaturation process of Spirulina to yield gamma-linolenic acid (GLA) as the final desaturation product. In this study, Spirulina-Delta(6) desaturase encoded by the desD gene was heterologously expressed and characterized in Saccharomyces cerevisiae. We then conducted site-directed mutagenesis of the histidine residues in the three histidine boxes to determine the role of these amino acid residues in the enzyme function. Our results showed that while four mutants showed complete loss of Delta(6)-desaturase activity and two mutants showed only trace of the activity, the enzyme activity could be partially restored by chemical rescue using exogenously provided imidazole. This study reveals that the histidine residues (which have imidazole as their functional group) in the conserved clusters play a critical role in Delta(6)-desaturase activity, possibly by providing a di-iron catalytic center. In our previous study, this enzyme was expressed in Escherichia coli. The results reveal that the enzyme can function only in the presence of an exogenous cofactor, ferredoxin, provided in vitro. This evidence suggests that baker's yeast has a cofactor that can complement ferredoxin, thought to act as an electron donor for the Delta(6) desaturation in cyanobacteria, including Spirulina. The electron donor of the Spirulina-Delta(6) desaturation in yeast is more likely to be cytochrome b(5), which is absent in E. coli. This means that the enzyme expressed in S. cerevisiae can catalyze the biosynthesis of the product, GLA, in vivo. << Less

  Mol. Biol. Rep. 32:215-226(2005) [PubMed] [EuropePMC]

• An in vivo study of substrate specificities of acyl-lipid desaturases and acyltransferases in lipid synthesis in Synechocystis PCC6803.

  Higashi S., Murata N.

  The cyanobacterium Synechocystis PCC6803 was fed heptanoic acid to study the substrate specificities of desaturases and acyltransferases in lipid synthesis. This aliphatic acid was elongated to C15, C17, and C19 fatty acids, which were incorporated into polar glycerolipids and desaturated. The dou ... >> More

  The cyanobacterium Synechocystis PCC6803 was fed heptanoic acid to study the substrate specificities of desaturases and acyltransferases in lipid synthesis. This aliphatic acid was elongated to C15, C17, and C19 fatty acids, which were incorporated into polar glycerolipids and desaturated. The double bonds were located at the [delta]6, [delta]9, [delta]12, and [omega]3 positions of the fatty acids. This suggests that the [delta]9 desaturase counts the carbon number from the carboxy terminus, whereas the so-called [delta]15 desaturase counts from the methyl terminus. The counting mechanisms of the [delta]6 and [delta]12 desaturases are not fully understood. In the distribution of fatty acids at the sn positions of the glycerol moiety, the C17, C18, and C19 fatty acids were located at the sn-1 position, whereas the C15 and C16 fatty acids were located at the sn-2 position. This suggests that glycerol-3-phosphate acyltransferase specifically transfers heptadecanoic, octadecanoic, and nonadecanoic acids, whereas 1-acylglycerol-3-phosphate acyltransferase specifically transfers pentadecanoic and hexadecanoic acids. << Less

  Plant Physiol. 102:1275-1278(1993) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Expression of a cyanobacterial delta 6-desaturase gene results in gamma-linolenic acid production in transgenic plants.

  Reddy A.S., Thomas T.L.

  Gamma-linolenic acid (GLA), a nutritionally important fatty acid in human and animal diets, is not produced in oil seed crops. Many oil seed plants, however, produce significant quantities of linoleic acid, a fatty acid that could be converted to GLA by the enzyme delta 6-desaturase if it were pre ... >> More

  Gamma-linolenic acid (GLA), a nutritionally important fatty acid in human and animal diets, is not produced in oil seed crops. Many oil seed plants, however, produce significant quantities of linoleic acid, a fatty acid that could be converted to GLA by the enzyme delta 6-desaturase if it were present. As a first step to producing GLA in oil seed crops, we have cloned a cyanobacterial delta 6-desaturase gene. Expression of this gene in transgenic tobacco resulted in GLA accumulation. Octadecatetraenoic acid, a highly unsaturated, industrially important fatty acid, was also found in transgenic tobacco plants expressing the cyanobacterial delta 6-desaturase. This is the first example of engineering the production of 'novel' polyunsaturated fatty acids in transgenic plants. << Less

  Nat Biotechnol 14:639-642(1996) [PubMed] [EuropePMC]