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Research article2000Peer reviewed

Characterisation of acyl-ACP desaturases from Macadamia integrifolia Maiden & Betche and Nerium oleander L.

Gummeson, Per Olof; Lenman, Marit; Lee, Michael; Singh, Surinder P.; Stymne, Sten

Abstract

The seed oil in Macadamia integrifolia contains about 30% palmitoleic acid (16:1(Delta 9)) and Nerium oleander about 12% isoricinoleic acid (Delta 9-hydroxy-18:1(Delta 12)). It has been shown that palmitoleic acid can be produced by acyl-acyl carrier protein (ACP) desaturases and it has also been shown that fatty acid hydroxylation can occur via direct substitution of a hydrogen atom. Therefore it seemed possible that the enzymes responsible for the making of these unusual fatty acids in M. integrifolia and N. oleander were of acyl-ACP desaturase type. Extracts from developing M. integrifolia developing seeds showed a relative ratio of 16:0-ACP to 18:0-ACP desaturation that was about 13 times higher than in sunflower seeds. N. oleander seed extracts catalysed conversion of 18:0-ACP to 18:1(Delta 9) but only trace amounts of Delta 9-hydroxy fatty acids were formed. A total of four cDNAs were isolated from developing seeds, of both species, using a fragment isolated with PCR amplification. The M. integrifolia acyl-ACP desaturase cDNA was expressed in Escherichia coli. A partly purified fraction of the enzyme showed a 16:0-ACP to 18:0-ACP desaturation ratio about 90-fold less than that in the Macadamia extracts. Expressed N. oleander acyl-ACP desaturase cDNAs showed predominantly 18:0-ACP desaturase activity and no hydroxylase activity. Thus it is not likely that any of the four acyl-ACP desaturases cloned from M. integrifolia or N. oleander is involved in the production of unusual fatty acids. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.

Keywords

acyl-ACP desaturase; Macadamia integrifolia; Nerium oleander

Published in

Plant Science
2000, Volume: 154, number: 1, pages: 53-60
Publisher: ELSEVIER SCI IRELAND LTD

      SLU Authors

    • Gummeson, Per Olof

      • Department of Plant Breeding Research, Swedish University of Agricultural Sciences

      • Lenman, Marit

        • Department of Plant Breeding Research, Swedish University of Agricultural Sciences

        • Stymne, Sten

          • Department of Plant Breeding Research, Swedish University of Agricultural Sciences

        UKÄ Subject classification

        Biochemistry and Molecular Biology

        Publication identifier

        DOI: https://doi.org/10.1016/S0168-9452(99)00268-X

        Permanent link to this page (URI)

        https://res.slu.se/id/publ/52294