Biological Properties of Peptidolipids

Most peptidolipids of the type discussed earlier exhibit antibiotic properties against various species of bacteria. For example, iturin A is 

Many of these peptidolipids have amphiphilic properties. This is illustrated by the protoplast-bursting activity of surfactin (93) or by the strong lysing activity of iturin A (but not iturin C) and bacillomycin L on erythrocytes (166), or the disruption of the outer membrane of Escherichia coli by EM 49 (152). Likewise antibiotics of the iturin group increased the size of small unilamellar vesicles of saturated lecithins (167). Differences in the balance between the hydrophobicity of the hydrocarbon chain and the polarity of the peptide moiety might explain the differences of action of iturin A, mycosubtilin and bacillomycin on Micrococcus luteus cells and protoplasts (168). 

Peptidolipid A21978 C displayed antibiotic activity against Gram positive bacteria. Enzymatic hydrolysis by incubation with Actinoplanes utahensis resulting in removal of the fatty acid was followed by chemical attachment of another fatty acid. Of the various analogues prepared in this manner, the n-decanoyl analogue (daptomycin) had the least acute toxicity in the mouse and exhibited antimicrobial properties at about 0,5 ig/ml (127). 

Acylpeptides with structures similar to that of surfactin were found to be inhibitors of cyclic adenosine-3, 5 -monophosphate phosphodiesterase. Opening of the lactone ring reduced the inhibitory activity to about one half that of the intact compound 101). 

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