Lipid Metabolism of Euglena Gracilis.
نویسندگان
چکیده
In both plants and animals pathways exist for the conversion of oleic acid to polyenoic acids (1, 2), but these pathways lead to different end products in the two kingdoms. In green plants the double bond system is extended toward the methyl end of the molecule to form linoleic and linolenic acids (9,12, lBoctadecatrienoic acid) (1,3,4). The ciliated protozoa, the amoebae, and some other animal protists share the ability of plants to convert oleic acid to linoleic acid, but all additional double bonds enter in the direction of the carboxyl group of the molecule (5, 6). In higher animals, linoleic acid is not synthesized, but when obtained from the diet, linoleic acid is desaturated to 6,9,12octadecatrienoic acid and then converted to arachidonic acid by chain elongation and further carboxyl-directed desaturation (2). The phytoflagellate Euglena gracilis is a protist which exhibits the metabolic behavior of a plant in the light and of an animal in the dark, and it has been shown that this organism synthesizes cu-linolenic acid as well as CzO polyenoic acids of the animal type (7, 8). Grown in the dark as a strict heterotroph, this organism contains large amounts of polyenoic CzO acids, including arachidonic acid, and little or no linolenic acid. On the other hand, Euglena cells growing under photoauxotrophic conditions are rich in linolenic acid and contain relatively small amounts of the C& polyenoic acids (7). The physiological significance of the synthesis of linolenic acid in photosynthetic Euglena has previously been discussed (8). We now wish to describe in more detail the identification of some of the polyenoic acids that occur in photoauxotrophic (grown in light, green) and heterotrophic (grown in dark, etiolated) euglenids and the pathways by which these acids are formed. The lipid types synthesized by Euglena in the light and in the dark have also been examined. Related studies were carried out with the colorless euglenid Astasia longa.
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 239 شماره
صفحات -
تاریخ انتشار 1964