Description
The lipid molecules in the cell membrane of Thermus thermophilus have numerous characteristics suitable for a high temperature environment compared with the standard phospholipids of mesophilic bacteria, such as the addition of iso or ante-iso branched fatty acids, the difference in the number of hydrophobic fatty acid side chains (three instead of two), a glycolipid as the major lipid and so on. In addition, a monosaccharide is attached to a T. thermophilus phospholipid and forms a phosphoglycolipid. The structures of the three main lipid molecules, namely two glycolipid molecules and one phosphoglycolipid molecule, have been determined. In particular, phosphoglycolipids (PGL and PGLN) are synthesized from two types of hydrocarbon chains; blanched fatty acids and aliphatic amines.
The phospholipid biosynthesis pathway originates with leucine as a starting material, and isovaleryl-CoA is initially synthesized. Malonyl-CoA, which is synthesized from acetyl-CoA, binds to isovaleryl-CoA to form branchedchain-acetyl-[acp]. Then, it is converted to isoheptyl-[acp] and further combined with malonyl-CoA again, increasing the carbon chain length by C2 (forming a loop reaction). This loop is repeated 6 times, and a terminally branched fatty acid (iso-C17:0) is synthesized. If the loop is repeated 5 times, iso-C15 is synthesized. When isoleucine or valine are used as starting materials instead of leucine and loop is repeated 7 times, anteiso-C17:0 or iso-C16:0 are synthesized, respectively.
References
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