Identification of three novel ostricacins: an update on the phylogenetic perspective of beta-defensins.

Three new beta-defensins, ostricacins-2, 3 and 4 (Osp-2, 3 and 4), have been successfully purified and characterised from ostrich heterophils in addition to ostricacin-1 (Osp-1). These peptides are composed of 36-42 amino acids with a molecular weight range of 4.70-4.98 kDa. In vitro, Osp-1, 3 and 4 were active against Escherichia coli O157:H7 and Staphylococcus aureus 1056 MRSA, whilst Osp-2 was active against bacterial strains plus the yeast Candida albicans 3153A. Minimal inhibitory concentrations of the three ostricacins ranged from 0.96 microg/mL to 12.03 microg/mL. Comparison with the known beta-defensins from mammalian and other avian species revealed that the four ostricacins shared eight conserved residues (six cysteines and two glycines), identified as the 'beta-defensin core motif'. Comparisons of the sequence also indicated that beta-defensins could have originated from a common beta-defensin-like ancestor that occurred before avian and mammalian lines diverged.

Avian antimicrobial peptides: the defense role of beta-defensins.

Avian antimicrobial peptides, classified as beta-defensins, have been identified from bloods of chicken, turkey, and ostrich; epithelial cells of chicken and turkey; and king penguin stomach contents. Beta-defensins are a family of antimicrobial peptides characterized by six cysteine residues forming beta-defensin motifs that are also found in bovine, ovine, pig, and human. These peptides are active against a wide range of microorganisms including Gram-positive and Gram-negative bacteria, fungi, and yeast. Analysis of evolutionary relationships of vertebrate beta-defensins showed that there might be a common ancestral gene between avian and other mammalian peptides. This ancient gene may have been passed down and evolved from species older than the oldest living birds, forming a beta-defensin-like precursor molecule. This review describes potential applications of these peptides in health care products.