Elementary plant Biochemistry and Biotechnology (2+1)

Sphingophospholipids

• The phosphate and fatty acids are attached to the alcohol sphingosine instead of glycerol in sphingophospholipids.
• The fatty acids are attached through an amide linkage rather than the ester linkage.
• The base present is normally choline.
• The structure of the parent compound sphingosine and phytosphingosine are shown below
• C-1, C-2 and C-3 of the sphingosine or phytosphingosine bear functional groups,-OH, -NH2 and -OH respectively, which are structurally homologous with the three hydroxyl groups of glycerol.
• Carbon 4 to 18 in sphingosine and C-5 to 18 in phytosphinogsine resembles that of a fatty acid.
• When a fatty acid is attached by an amide linkage to the -NH2, group the resulting compound is a ceramide which is similar to diacyl glycerol
• Ceramide is the fundamental structural unit common to all sphingophospholipids
• Sphingophospholipids are found in the seeds of several plant species.
• There is a range of molecular species among the phospholipid sub groups which differ from one another in the fatty acid composition
• All the sub groups of phospholipids are found in plant photosynthetic tissue
• Animal phospholipids contain mostly fatty acids with chain length between 16 and 20. The predominant fatty acids are palmitic, stearic, oleic, linoleic and arachidonic.
• Plant leaf phospholipids have a more limited range with very few fatty acids greater than C-18.
• The approximate proportion of each phospholipid expressed as a percentage of the total phospholipid present is phosphatidyl choline, 45%; phosphatidyl ethanolamine, 10%;
• Trace amounts of phosphatidyl serine, phosphatidyl inositol, 8%; monophosphatidyl glycerol, 35%, diphosphatidylglycerol, 2%.
• The diphosphatidyl glycerol is present in the inner mitochondrial membrane.
• The phospholipids are only minor components of seed lipids in which triacylglycerol predominate.
• The most abundant mammalian phospholipid is phosphatidyl choline.
• The phospholipids carry an electrical charge and interact with water. They are called as polar or hydrophilic molecules and also as amphiphilic molecules.
• The sphingomyelins, the main sphingophospholipids of animals, are not present in plants.