Antimicrobia
747
Part F | 31.2
31. Antimicrobial Peptides from Marine Organisms
Venugopal Rajanbabu, Jyh-Yih Chen, Jen-Leih Wu
Antimicrobial peptides (AMP), also known as host
defense peptides or alarmins, are among the first
lines of defense against infection in many organisms. Marine organisms have proved to be a rich
source of AMPs, and several uniquely structured
marine AMPs have been isolated using biochemical, in silico and genetic approaches. Hemolymph
is the main source of AMPs in marine invertebrates, although other tissues may also contain
these peptides. Based on their three-dimensional
structure, AMPs may be classified into peptides
with ˛-helix structures, peptides with ˇ-sheets
and cysteine residues, peptides enriched for modified and rare amino acids, and peptides with ring
structure amino acids. This chapter describes AMPs
of each structure, in terms of their antibacterial,
antiviral, antifungal, insecticidal, nematicidal, and
immunomodulatory functions. It is hoped that the
diversity of marine AMPs may facilitate the iden31.1 Marine Antimicrobial Peptides.............. 747
31.2 Isolation of Antimicrobial Peptides ....... 748
31.3 Characterization and Functions
of AMP ................................................ 748
31.3.1 Alpha Helical AMPs .................... 748
31.3.2 Beta Sheet/Cysteine-Rich AMPs ... 749
31.3.3 AMPs with Coil Structure
and Modified Amino Acids ......... 752
31.3.4 Ring Structured AMPs ................. 753
31.4 Future Directions
in Marine AMP Applications .................. 753
References................................................... 755
tification of effective substitutes to existing
antibiotics, thereby helping to minimize the development of antibiotic-resistant pathogen strains
in response to the continuous application of a single antibiotic therapy.
31.1 Marine Antimicrobial Peptides
Antimicrobial peptides (AMP) are short amino acid
chain molecules involved in the first line of defense against invading pathogens. AMPs are synthesized by the ribosomal machinery as pro-peptides,
consisting of an N-terminal signal sequence, a prosequence, and a C-terminal sequence with antimicrobial activity once it is cleaved from the rest of the
pro-peptide.
To date, nearly 3000 AMPs have been isolated
from organisms as diverse as plants, mammals, fish
(marine, fresh water and aquaculture), and insects
and other invertebrates. Marine organisms produce numerous AMPs to combat specific and large invading
pathogens in an aquatic environment. Marine organisms are relatively understudied, and only a presumed
fraction of marine AMPs has been identified. As such,
it is likely that with further research we will isolate
a considerable number of AMPs from marine sources.
In a similar manner to the development of drug resistance, pathogens evolve to evade host AMPs. By
targeting pathogens with functionally similar, yet structurally unique marine AMPs, it may be possible to
prevent the evolution of resistant strains. The growing interest in the study of marine AMPs has led
to the discovery of peptides similar to mammalian
equivalents, but with unique differences. This chapter
briefly describes the methods employed in the isolation
of marine AMPs, before describing the antimicrobial
functions and other applications of structurally grouped
AMPs.
747
Part F | 31.2
31. Antimicrobial Peptides from Marine Organisms
Venugopal Rajanbabu, Jyh-Yih Chen, Jen-Leih Wu
Antimicrobial peptides (AMP), also known as host
defense peptides or alarmins, are among the first
lines of defense against infection in many organisms. Marine organisms have proved to be a rich
source of AMPs, and several uniquely structured
marine AMPs have been isolated using biochemical, in silico and genetic approaches. Hemolymph
is the main source of AMPs in marine invertebrates, although other tissues may also contain
these peptides. Based on their three-dimensional
structure, AMPs may be classified into peptides
with ˛-helix structures, peptides with ˇ-sheets
and cysteine residues, peptides enriched for modified and rare amino acids, and peptides with ring
structure amino acids. This chapter describes AMPs
of each structure, in terms of their antibacterial,
antiviral, antifungal, insecticidal, nematicidal, and
immunomodulatory functions. It is hoped that the
diversity of marine AMPs may facilitate the iden31.1 Marine Antimicrobial Peptides.............. 747
31.2 Isolation of Antimicrobial Peptides ....... 748
31.3 Characterization and Functions
of AMP ................................................ 748
31.3.1 Alpha Helical AMPs .................... 748
31.3.2 Beta Sheet/Cysteine-Rich AMPs ... 749
31.3.3 AMPs with Coil Structure
and Modified Amino Acids ......... 752
31.3.4 Ring Structured AMPs ................. 753
31.4 Future Directions
in Marine AMP Applications .................. 753
References................................................... 755
tification of effective substitutes to existing
antibiotics, thereby helping to minimize the development of antibiotic-resistant pathogen strains
in response to the continuous application of a single antibiotic therapy.
31.1 Marine Antimicrobial Peptides
Antimicrobial peptides (AMP) are short amino acid
chain molecules involved in the first line of defense against invading pathogens. AMPs are synthesized by the ribosomal machinery as pro-peptides,
consisting of an N-terminal signal sequence, a prosequence, and a C-terminal sequence with antimicrobial activity once it is cleaved from the rest of the
pro-peptide.
To date, nearly 3000 AMPs have been isolated
from organisms as diverse as plants, mammals, fish
(marine, fresh water and aquaculture), and insects
and other invertebrates. Marine organisms produce numerous AMPs to combat specific and large invading
pathogens in an aquatic environment. Marine organisms are relatively understudied, and only a presumed
fraction of marine AMPs has been identified. As such,
it is likely that with further research we will isolate
a considerable number of AMPs from marine sources.
In a similar manner to the development of drug resistance, pathogens evolve to evade host AMPs. By
targeting pathogens with functionally similar, yet structurally unique marine AMPs, it may be possible to
prevent the evolution of resistant strains. The growing interest in the study of marine AMPs has led
to the discovery of peptides similar to mammalian
equivalents, but with unique differences. This chapter
briefly describes the methods employed in the isolation
of marine AMPs, before describing the antimicrobial
functions and other applications of structurally grouped
AMPs.