Abstract
Although the bioactivities of bovine lactoferrin have been extensively investigated, little is known about deer milk lactoferrin bioactivity and its amino acid sequence. This research investigated the amino acid sequence of deer lactoferrin and the antimicrobial activities of two lactoferrin-encrypted peptides; lactoferricin (Lfcin) and lactoferrampin (Lfampin). Deer lactoferrin was found to have a molecular weight of 77.1 kDa and an isoelectric point of 7.99, which are similar to that of bovine lactoferrin, 78 kDa and pI 7.9. Deer lactoferrin contains 707 amino acids, one amino acid less than bovine lactoferrin, and has 92% homology with bovine lactoferrin. Deer lactoferricin exhibited strong antimicrobial activity against E. coli American Type Culture Collection (ATCC) 25922 and L. acidophilus ATCC 4356. The antimicrobial activities of deer and bovine Lfcin and Lfampin were compared. Based on MIC, deer Lfcin was found to be a more effective inhibitor of L. acidophilus ATCC 4356 than bovine Lfcin, but bovine Lfcin and Lfampin were more effective against E. coli ATCC 25922 than deer Lfcin and Lfampin. The deer Lfcin sequence differed at seven amino acids from bovine Lfcin and this decreased the net positive charge and increased the hydrophobicity. Deer Lfampin contained two differences in amino acid sequence compared to bovine Lfampin which decreased the net positive charge. These amino acid sequence differences likely account for differences in antibacterial activity. Positive charge and hydrophobic residues provide the amphipathic character of these helical peptides, and are considered important for binding of antimicrobial peptides. In silico modelling of deer Lfcin indicated an identical α-helical structure compared to bovine Lfcin.
Highlights
Introduction published maps and institutional affilThe extended use of antibiotics has led to antibiotic resistance which threatens global health and food security
Bacterial strains used in antibacterial activity assays (Escherichia coli American Type Culture Collection (ATCC) 25922, Staphylococcus aureus ATCC 25923, and L. acidophilus ATCC 4356) were from ESR (Christchurch, Canterbury, New Zealand)
Of bovine Lfampin against E. coli ATCC 25922 was found to be 480 μg/mL. These results indicate that at an equivalent concentration, bovine Lfcin and Lfampin were more active as antimicrobial inhibitors of E. coli ATCC 25922 growth than deer Lfcin and Lfampin
Summary
The extended use of antibiotics has led to antibiotic resistance which threatens global health and food security. Antimicrobial peptides have potential as alternatives to antibiotics. A typical antimicrobial peptide can have a higher isoelectric point, better thermal stability, broader-spectrum antimicrobial properties, and can be more amenable to preparation in a sterile form [1]. It has been suggested that antimicrobial peptides should not cause widespread resistance, due to their preferential attack on bacterial cell membranes [2]. Dairy products are an important source of antimicrobial peptides [3]. There has been a dramatic increase in the farming of red deer recently and emergence of deer milk dairying, deer milk could provide a potential alternative source of antimicrobial peptides [4,5]
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