Lipids in potatoes

The membrane lipids, in particular phospholipids and galactolipids, make up the predominant fraction of lipids in potato tubers, and only trace amounts of triacylglycerols are present. For example, in the tuber of cultivar Desiree, the membrane lipids constitute 92.8 mol-% of total lipids, whereas triacylglycerol amounts to only 1.1 mol-% (Klaus et al., 2004). 

Galliard, T. (1968). Aspeets of lipid metabolism in higher plants-I. Identification and quantitative determination of the lipids in potato tubers. Phytochemistry, 7, 1907-1914. 

R. A. Moreau and T. S. Isett, Autolysis of membrane lipids in potato... 

Galliard T. The enzymatic breakdown of lipids in potato tuber by phospholipid and galactolipid acyl-hyrolase activities and by lipoxygenase. Phytochemistry 1970 9 1725-1734. 

Faueonnier, M. L., Welti, R., Blee, E., Marlier, M. (2003a). Lipid and oxylipin profiles during aging and sprout development in potato tubers (Solanum tuberosum L.). Biochim. Biophys. Acta, 1633,118-126. 

The patatin family consists of various glycoproteins in plants making up more than 40% of the total soluble protein in potato tubers. Patatins serve as storage proteins and it has been demonstrated that they exhibit both lipid acyl hydrolase and acetyl transferase activities, which might be involved in tissue wounding responses. Further, recent studies report on antioxidant activities of the major potato allergen Sola t 1 (Seppala et al. 2000). 

Swinkels29 collected published characterization data for tapioca starch and compared it to that for other starches of commercial significance (Table 12.4). Tapioca starch is differentiated from other starches by its low level of residual materials (fat, protein, ash), lower amylose content than for other amylose-containing starches, and high molecular weights of amylose and amylopectin. The small amount of phosphorus in tapioca starch is partially removable30 and, therefore, not bound as the phosphate ester as in potato starch. It is also common to find protein and lipid values of zero, as reported by Hicks.31 The very low protein and lipid content is an important factor which differentiates tapioca starch from the cereal starches. 

Lipids are not evenly distributed in starch granules. A certain proportion resides on the surfaces of granules (endosperm), and usually a much higher proportion resides as internal starch lipids. All of them are monoacyl glycerides, free fatty acids, and lysophospholipids. Cereal materials contain mainly internal starch lipids. Lipids of potato tubers reside in amyloplasts and are... 

Saccharides are present in food raw materials in quantities ranging from about 1% in meats and fish, to about 4.5% in milk, 18% in potatoes, and 15-20% in sugar beets, to about 70% in cereal grains. Polysaccharides participate in the formation of structures in plants. They are also stored in plants as starch and in muscles as glycogen. Other saccharides are dissolved in tissue fluids or perform different biological functions in free nucleotides, as components of nucleic acids, or bound to proteins and lipids. 

Salinas, J.P et al., Lipid derived aroma compounds in cooked potatoes and reconstituted dehydrated potato granules, in Lipids in Food Flavors, Ho, C.T. and Hartman, T.G., Eds., American Chemical Society, Washington, D.C., 1994, p. 108. 

Other isopentenoids. Many lipids other than steroids ere formed via the isopentenoid pathway. Terpenes and their derivatives are very important in interactions of plants with other organisms. Kuc and coworkers have proposed that fungal elicitors modify isopentenoid pathways in potato, shifting biosynthesis from triterpene alkaloids which are pre-infection inhibitors to sesquiterpene lactone stress metabolites (9). A variety of insect attractants, insect juvenile hormones, inhibitors and plant hormones are terpene derivatives. 

In our preliminary studies of the infection of susceptible potato leaves by P. infestans we also observed a similar rapid degradation of glycolipids and phosphatidyl glycerol. However, upon further investigation we realized that the unique composition of membrane lipids in P. infestans may provide a useful marker during infection. The polar lipid conq>osltion of healthy potato leaves and cultured P. infestans is shown in Table I. The lipid... 

The following experiments illustrate that when studying the involvement of phospholipase in the host-pathogen interaction, the total contribution of enzyme of host origin may be considerably higher than previously realized. Rodionov and Zakharova (32) recently reported very high rates of autolytic hydrolysis of membrane lipids in homogenates of potato leaves (26-37% of the phospholipids were hydrolyzed after 2 h at 0-1 ). Our laboratory recently confirmed this observation and proceeded to study sosie of the properties of the lipolytic acyl hydrolase activity in potato leaves (6). Lipolytic acyl hydrolase activity is apparently inactivated by polyphenol oxidase or its toxic quinone products. 

The work of Owens and Northcote (1981) has produced convincing evidence that the Golgi apparatus is the site of assembly of these sequences and that similar mechanisms operate to assemble them in potato lectin and cell wall glycoproteins. What is now needed is a search for lipid-linked intermediates and the isolation and characterisation of the transferases involved. 

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