Lichenysin: a more efficient cation chelator than surfactin
Abstract
The lipopeptide lichenysin (cyclo-[L-Gln1-->D-Leu2-->L-Leu3-->L-Val4--> L-Asp5-->D-Leu6-->L-Ile7-beta-OH fatty acid]) produced by Bacillus licheniformis structurally resembles surfactin from Bacillus subtilis. The main difference is the presence of a glutaminyl residue in position 1 of the peptide sequence in place of glutamic acid in surfactin. This local variation causes significant changes in the properties of the molecule compared to surfactin. Lichenysin has a higher surfactant power, the critical micellar concentration (c.m.c.) being strongly reduced from 220 to 22 microM and a much higher hemolytic activity because 100% hemolysis was observed with only 15 microM instead of 200 microM. Lichenysin is also a better chelating agent because its association constants with Ca2+ and Mg2+ are increased by a factor of 4 and 16, respectively. This effect is assigned to an increase in the accessibility of the carboxyl group to cations owing to a change in the side chain topology induced by the Glu/Gln exchange. Additionally, the propensity of the lipopeptide for extensive hydrophobic interactions, as illustrated by its low c.m.c., contributes to further stabilization of the cation and an increase in the partitioning of lichenysin in...Continue Reading
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Recent Advances in Biomedical, Therapeutic and Pharmaceutical Applications of Microbial Surfactants.
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