Biogenesis of mitochondria 19 the effects of unsaturated fatty acid depletion on the lipid composition and energy metabolism of a fatty acid desaturase mutant of |
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Authors: | J W Proudlock J M Haslam Anthony W Linnane |
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Institution: | 1. Department of Biochemistry, Monash University, 3168, Clayton, Victoria, Australia
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Abstract: | - The lipid composition of a mutant ofSaccharomyces cerevisiae which cannot synthesize unsaturated fatty acid (UFA) can be extensively manipulated by growing the organism in the presence of added fatty acids.
- Growth of the mutant is supported by a wide range of unsaturated fatty acids including oleic, palmitoleic, petroselenic, 11-eicosaenoic, ricinoleic, arachidonic, clupanodonic, linoleic and linolenic acids; 9- and 10-hydroxystearic acids support growth less effectively, but erucic, nervonic, elaidic and saturated fatty acids (C8∶0?C20∶0)* are ineffective. All the fatty acids which support growth are incorporated into cell lipids, apparently without further metabolism.
- The effects of altered lipid composition on the energy metabolism of yeast cells were investigated. Cells containing less than approximately 20% of their fatty acids as UFA cannot grow on non-fermentable substrates, and their growth on glucose is restricted to that which can be supported by fermentation alone.
- UFA-depleted cells contain mitochondria which are apparently normal in morphology, furthermore they have normal levels of cytochromesa+a 3,b,c 1 andc and respire at normal rates. This suggests that the lesion in energy metabolism produced by UFA-depletion may be the loss of the ability of the mitochondria to couple respiration to phosphorylation.
- UFA-depleted cells incorporate added UFA into their cell lipids and subsequently regain the ability to grow on non-fermentable substrates, showing that the lesion in energy metabolism is fully reversible.
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