ReviewOverview on the recent study of antimicrobial peptides: Origins, functions, relative mechanisms and application
Highlights
► Antimicrobial peptides (AMPs) produced by several species including insects, other animals, micro organisms and synthesis, are a critical component of the natural defense system. ► With the growing problem of pathogenic organisms resistant to conventional antibiotics, especially with the emergence of NDM-1, there is increased interest in the pharmacological application of AMPs. ► They can protect against a broad array of infectious agents, such as bacteria, fungi, parasite, virus and cancer cells. ► AMPs have a good future in the application in pharmaceuticals industry and food additive.
Introduction
Antimicrobial peptides (AMPs) are gene-encoded, ribosomally synthesized polypeptides. They usually have the common characteristics: small peptide (30–60 aa), strong cationic (pI 8.9–10.7), heat-stable (100 °C, 15 min), no drug fastness and no effect on eukaryotic cell. The natural AMPs have been isolated and characterized from practically all-living organisms, ranging from prokaryotes to humans. The AMPs produced by bacteria are also termed ‘bacteriocins’ [5], [6]. AMPs usually work against bacteria that are closely related to the producer strains in prokaryotes, while they play a key role in innate immunity in eukaryotes. These peptides are produced by several species including bacteria, insects, plants, vertebrates and they have been recognized as ancient evolutionary molecules that have been effectively preserved in mammals [1], [50].
In 2008, a Swedish patient of Indian origin traveled to New Delhi (India) and acquired a urinary tract infection caused by a carbapenem-resistant Klebsiella pneumoniae strain that typed to the sequence type 14 complex. The isolate, K. pneumoniae 05–506, was shown to possess a metallo-β-lactamase (MBL) but was negative for previously known MBL genes [103]. This enzyme hydrolysing all β-lactams except aztreonam is commonly identified in multidrug-resistant isolates and we name this kind of organisms as NDM-1 (It stands for New Delhi metallo-beta-lactamase 1). It is coded by blaNDM-1 or NDM-1 gene which encodes, 269 amino acids containing protein, with molecular mass of approx 27.5 kDa [15]. The spread of these organisms has prompted widespread concern because some of them are resistant to the vast majority of antimicrobial agents [51], [77]. Since antibiotic resistance to conventional antibiotics is occurring, there is increased interest in the pharmacological application of AMPs. An updated database of AMPs is available on line at: http://aps.unmc.edu/AP/main.php [95].
The significant advantage of AMPs resides in the global mechanism of their action, which is remarkably different from that of conventional antibiotics. Usage of AMPs will gain widespread increase since more and more bacteria may develop the ability to resist conventional antibiotics due to the abuse of these drugs worldwide. This article will summarize the recent AMPs and their relative mechanisms from various origins.
Section snippets
Origins of AMPs
AMPs can be commonly classified into four groups according to their origins. They are from insects, other animals, synthesis and genetically engineered microorganism. To date more than 1500 AMPs of different origins have been reported [34].
Different functions of AMPs
AMPs display multifunctional properties with implications as potential therapeutic agents. They exhibit rapid killing, often within minutes in vitro, and a broad spectrum of activity against Gram-positive and Gram-negative bacteria, fungi, parasites, enveloped viruses and tumor cells. In these several years, they have been termed “natural antibiotics”, because they are active against a large spectrum of microorganisms including bacteria, filamentous fungi, protozoan and metazoan parasites. It
Conclusions
Drug resistance is a major problem in antibacterial chemotherapy, and AMPs may solve this problem in the future. AMPs are currently in the spotlight as potential candidates to overcome bacterial resistance to conventional antibiotics. Many AMPs have multi-functions such as antibacterial, antifungal and anti-cancer activities. Because they are able to rapidly kill broad range of infectious agents and modulate both innate and adaptive immunity, considerable efforts have been made to exploit their
Acknowledgment
This work is supported by major project of Guangdong Province Department of Education (cgzhzd0710).
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