A. Lesley Jones

Lipid Metabolism in Algae

Publisher Summary The lipid composition and metabolism of algae are exceptionally varied. This chapter focuses on groups of organisms (algae) that have been studied in reasonable detail. To lay a basis for further discussion of metabolism, the lipid structure and occurrence in algae is discussed. The metabolic sections then deal with organisms of increasing complexity, from the primitive cyanobacteria to marine macroalgae. Finally, the chapter ends with a discussion on green algae, which can be regarded as the nearest in metabolic characteristics to higher plants.

Insoluble TATA-binding protein accumulation in Huntington’s disease cortex

Huntingtons disease is a dominantly inherited neurological disorder where specific neurodegeneration is caused by an extended polyglutamine stretch in the huntingtin protein. Proteins with expanded polyglutamine regions have the ability to self-aggregate and previous work in our laboratory, and by others, revealed sparse amyloid-like deposits in the Huntingtons disease brain, supporting the hypothesis that the polyglutamine stretches may fold into regular beta-sheet structures. This process of folding has similarities to other neurodegenerative disorders including Alzheimers disease, Parkinsons disease, and the prion diseases which all exhibit beta-sheet protein accumulation. We were therefore interested in testing the hypothesis that TATA-binding protein may play a role in Huntingtons disease as it contains an elongated polymorphic polyglutamine stretch that ranges in size from 26 to 42 amino acids in normal individuals. A proportion of TBP alleles fall within the range of glutamine length that causes neurodegeneration when located in the huntingtin protein. In this study the distribution and cellular localisation of TATA-binding protein was compared to the distribution and cellular localisation of the huntingtin protein in the middle frontal gyrus of Huntingtons disease and neurologically normal subjects. Seven different morphological forms of TATA-binding protein-positive structures were detected in Huntingtons disease but not in control brain. TATA-binding protein labelling was relatively more abundant than huntingtin labelling and increased with the grade of the disease. At least a proportion of this accumulated TBP exists as insoluble protein. This suggests that TBP may play a role in the disease process.

Lipid composition of the brown algae fucus vesiculosus and Ascophyllum nodosum

Abstract The lipid composition of the two brown marine algae, Fucus vesiculosus and Ascophyllum nodosum, was very similar. The major acyl lipids were monogalactosyldiacylglycerol, digalactosyldiacylglycerol, sulphoquinovosyidiacylglycerol and trimethyl-β-alaninediacylglycerol. The major phospholipid was phosphatidylethanolamine but this represented less than 10% of the total acyl lipids. Monogalactosyldiacylglycerol was the most unsaturated lipid, with high proportions of eicosapentaenoic and octadecatetraenoic acids and sulphoquinovosyidiacylglycerol was the most saturated glycolipid with high proportions of palmitate and oleate. The phospholipids phosphatidylcholine and phosphatidylethanolamine had very similar fatty acid patterns, with around 60% of their acyl chains being arachidonic acid. In Fucus vesiculosus the galactosyldiacylglycerides had most of the 16C acyl chains esterified at the sn-1 position. α-Linolenic acid and eicosapentaenoic acid were also mostly esterified to the sn-1 position while octadecatetraenoic acid was concentrated at the sn-2 position. Both sulphoquinovosyldiacylglycerol and phosphatidylglycerol showed typically prokaryotic positional distribution of fatty acids with 16C chains concentrated at the sn-2 position. Of these, trans-Δ3-hexadecenoic acid was exclusively esterified to the sn-2 position of phosphatidylglycerol.

Lipid metabolism in the red marine algae Chondrus crispus and Polysiphonia lanosa as modified by temperature

Abstract Effects of temperature on lipid content in vivo and metabolism in vitro were studied in the two red marine algae, Chondrus crispus and Polysiphonia lanosa. The amounts of phosphatidylglycerol, triacylglycerol and non-esterified fatty acid increased during the winter in P. lanosa, as did the degree of unsaturation. The proportion of radiolabel from [14C]-acetate in diglycosyldiacylglycerol and sulphoquinovosyldiacylglycerol in vitro increased with rising temperature in C. crispus while that for phosphatidylglycerol fell. Rising temperature also increased the proportion of radiolabelling in myristate and palmitate while reducing that for oleate in both algae. These results are discussed in terms of adaptation to changed environmental temperatures and mechanisms for the control of membrane lipid fluidity.

Lipids and lipid metabolism in the marine alga Enteromorpha intestinalis

The major acyl lipids of the marine alga, Enteromorpha intestinalis are the glycosylglycerides, monogalactosyldiacylglycerol, digalactosyldiacylglycerol and sulphoquinovosyldiacylglycerol. The only important phospholipid is phosphatidylglycerol and the only other lipid present in any quantity is diacylglyceryltrimethylhomoserine. The acyl chain distributions of these lipids were analysed. Labelling from [1-C-14]acetate indicated that oleate was the major product of de novo fatty acid synthesis. At higher incubation temperatures more radiolabel was incorporated into saturated fatty acids than at lower temperatures.

Effect of thiolactomycin on fatty acid synthesis in peas

Abstract Thiolactomycin inhibited fatty acid synthesis in isolated pea chloroplasts. Using [1- 14 C]acetate as a precursor, an I 50 value of ca 20 μM was obtained for a ( R , S ) mixture of thiolactomycin. The antibiotic inhibited the β-ketoacyl-ACP synthase (condensing enzyme: KAS) and the acetyl-CoA: ACP (ACAT) reactions. An examination of the relative inhibition of the three condensing enzymes revealed that their order of sensitivity to thiolactomycin was KAS II > KAS I > KAS III.

Inhibition of Fatty Acid Condensing Enzymes in Plants

Fatty acid synthesis in plants is carried out by a type I dissociable fatty acid synthase (FAS). There are three β-ketoacyl-ACP synthases (KAS) associated with FAS in plants. The short-chain condensing enzyme (KAS III) catalyses the initial condensation of acetyl-CoA with malonyl-ACP [1,2] to form acetoacetyl-ACP (4C) and may catalyse further rounds of condensation in vivo [3]. Further rounds of condensation are carried out by KAS I which catalyses the condensation of malonyl-ACP with intermediate length acyl-ACPs from acetoacetyl-ACP to myristoyl-ACP (14C) to give palmitoyl-ACP (16C). KAS II elongates palmitoyl-ACP (16C) to stearoyl-ACP (18C) [4].