LIPOAMINO ACIDS :
N-ACYL and ESTER DERIVATIVES of AMINO ACIDS
Several types of derivatives are known according to their amino acid moiety:
1 - Lysine-containing lipids
Some of them are known as Siolipin A. In these compounds lysine is N-linked to a fatty acid (normal or hydroxylated, R1) and to a fatty alcohol (R2) (ester link). They are found in Streptomyces species of bacteria.
2 - Ornithine-containing lipids
In these lipids ornithine is linked to a fatty acid (R1) by an amide link and to a long-chain fatty alcohol (R2) by an ester link.
The fatty acid chain (R1) has 16 to
18 carbon atoms and the fatty alcohol may have a cyclopropane ring. They occur
in photosynthetic purple bacteria (Gorshein A, Biochim Biophys Acta 1968,
Less complex forms containing ornithine linked to fatty acids only were also described.
Other ornithine-containing lipids are found in Gram negative bacteria and have been reported in some Gram-positives, like Mycobacterium and Streptomyces species but are absent in Archaea and Eukarya (Geiger O et al., Prog Lipid Res 2010, 49, 46). They are commonly formed of a 3-hydroxy fatty acyl group that is attached in amide linkage to the a-amino group of ornithine an a second fatty acyl group is ester-linked to the 3-hydroxy position of the first fatty acid.
3- Glycine-containing lipids
The glycine-containing lipids have been identified in the gliding bacterium Cytophaga johnsonae (Kawazoe R et al., J Bacteriol 199, 173, 5470) and the Gram-negative sea-water bacterium Cyclobacterium marinus (Batrakov SG et al., Chem Phys Lipids 1999, 99, 139). These lipids consist of the amino acid glycine and two fatty acyl residues, using the acyl-oxyacyl structure. The structure of glycine lipid from C. marinus is mainly a N-[3-D-(13-methyltetradecanoyloxy)- 15-methylhexadecanoyl]glycine (see figure below). In this structure, an iso-3-hydroxyfatty acyl group is amide-linked to glycine and its 3-hydroxy group is esterified to another iso-fatty acid.