Defensins antimicrobial activity

In addition to the cathelicidins and defensins, humans also utilize a variety of other host defense peptides. Examples of these include the anionic dermcidins, found in human sweat and possessing potent antimicrobial activity in a broad range of pH and salt concentrations, and the histatins, a histidine-rich host defense peptide family found in humans and higher primate species. The histatins are normally found in saliva and utilize an alternative mechanism to bacterial membrane lysis for their antimicrobial activity. ... 

Earlier investigations have indicated that the network of disulfide linkages found within /3-defensins is not required for antimicrobial activity. An investigation by Kliiver et al. has demonstrated that disulfide connectivity in a particular context is not required for antimicrobial activity. Indeed, HBD-3 derivatives lacking disulfide bonds were found to be as active as their cyclic analogues. This is in agreement with a previous study by Hoover et in which a linear variant of full-length HBD-3 retained antimicrobial activity... 

Vizioli, J., Richman, A.M., Uttenweiler-Joseph, S., Blass, C., and Bulet, P. (2001) The defensin of the malaria vector mosquito Anopheles gambiae antimicrobial activities and expression in adult mosquitoes. Insect Biochem. Mol. Biol. 31, 241-248. 

The plant was traditionally boiled in water to produce a medicinal tea that was used to accelerate childbirth. Reports of this use stimulated interest in characterising the bioactive component, which was subsequently found to be a 29 amino acid peptide referred to as kalata Bl.105 Cyclotides have also been reported to possess antimicrobial activity,106 and, for example, synthetic versions of the cyclotides circulin B and cyclopsychotride A are active against both Grampositive and Gram-negative bacteria.106 Impaired antimicrobial activity of cyclotides is observed at high salt concentration in the assay buffer and the phenomenon of activity linked to ionic strength has also been described for thionins and plant defensins and is an indicator of activity at membranes. 

Although historically most useful antibiotics have come from spore forming microorganisms, marine organisms have yielded the candidate antitumor peptide didemnin B [77327-50-0] (2) and cytostatic peptides such as the patellamides (3). Many of the marine peptides have little or no antimicrobial activity. Antibacterial peptides called magainins are found in frog skin (4) and antibacterial proteins called defensins are found in mammalian white blood cells (5). The commercially important insecticidal proteins from Bacillus thuringensis (6) are not discussed herein nor are the numerous peptide siderophores (7,8), which, except for the albomycins (9), are usually not antimicrobial. 

The skin, together with the gastrointestinal and respiratory tracts, are the areas which are constantly exposed to microbes and, consequently, they are the main locations of synthesis of antimicrobial peptides. Besides their direct antimicrobial activity, antimicrobial peptides released from circulating cells or induced in the epithelia can also promote a response of the adaptive immune system. Different possible modes of action have been suggested for a- and / -defensins. It was suggested that antimicrobial peptides enhance the recruit-... 

In addition to their direct antimicrobial activity [15] defensins, whose functional overlap with chemokines has recently been confirmed, enhance phagocytosis, promote neutrophil recruitment, boost the production of proinflammatory cytokines and regulate complement activation, thus upregulating innate host inflammatory defenses [15]. They also contribute to adaptive immune responses by selectively attracting immature DCs, CD8+ T cells,... 

Cole AM, Ganz T, Liese AM, Burdick MD, Liu L, Strieter RM. Cutting edge IFN-inducible ELR(—) CXC chemokines display defensin-hke antimicrobial activity. J Immunol 2001 167 623-627. 

CUESTA A, MESEGUER J, ESTEBAN MA (2011), Molecular and functional characterization of the gilthead seabream P-defensin demonstrate its chemotactic and antimicrobial activity . Mol Immunol, 48,1432-8. 

ZHAO JG, ZHOU L, JIN JY, ZHAO z, LAN J, ZHANG YB, ZHANG QY, GUI JF (2009), Antimicrobial activity-specific to Gram-negative bacteria and immune modulation-mediated NF-kappaB and Spl of a medaka beta-defensin , Dev Comp Immunol, 33,624-37. 

TRAN D, TRAN PA, TANG YQ, YUAN J, COLE T, SELSTED ME. Homodimeric theta-defensins from rhesns macaqne lenkocytes isolation, synthesis, antimicrobial activities, and bacterial binding properties of the cyclic jjeptides. J Biol Chem 2002 Feb l 277(5) 3079-84. 

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