Sensitivity of Pseudomonas syringae to Bovine Lactoferrin Hydrolysates and Identification of a Novel Inhibitory Peptide

The antimicrobial activity of bovine lactoferrin hydrolysates (bLFH) was measured against Pseudomonas strains (P. syringae and P. fluorescens) in vitro. To compare susceptibility to bLFH, minimal inhibitory concentration (MIC) values were determined using chemiluminescence assays and paper disc plate assays. Antimicrobial effect against P. fluorescens was not observed by either assay, suggesting that bLFH did not exhibit antimicrobial activity against P. fluorescens. However, a significant inhibition of P. syringae growth was observed in the presence of bLFH. The addition of bLFH in liquid or solid medium inhibited growth of P. syringae in a dose-dependent manner. Furthermore, a bLFH peptide with antimicrobial activity toward P. syringae was isolated and identified. The N-terminal amino acid sequences of thus obtained antimicrobial bLFH peptides were analyzed by a protein sequencer and were found to be Leu-Arg-Ile-Pro-Ser-Lys-Val-Asp-Ser-Ala and Phe-Lys-Cys-Arg-Arg-Trp-Gln-Trp-Arg-Met. The latter peptide sequence is known to be characteristic of lactoferricin. Therefore, in the present study, we identified a new antimicrobial peptide against P. syringae, present within the N-terminus and possessing the amino acid sequence of Leu-Arg-Ile-Pro-Ser-Lys-Val-Asp-Ser-Ala.

Inhibitory Effects of Synthetic Peptides Containing Bovine Lactoferrin C-lobe Sequence on Bacterial Growth

Lactoferrin is a glycoprotein with various biological effects, with antibacterial activity being one of the first effects reported. This glycoprotein suppresses bacterial growth through bacteriostatic or bactericidal action. It also stimulates the growth of certain kinds of bacteria such as lactic acid bacteria and bifidobacteria. In this study, Asn-Leu-Asn-Arg was selected and chemically synthesized based on the partial sequences of bovine lactoferrin tryptic fragments. Synthetic Asn-Leu-Asn-Arg suppressed the growth of Pseudomonas fluorescens, P. syringae and Escherichia coli. P. fluorescens is a major psychrotrophic bacteria found in raw and pasteurized milk, which decreases milk quality. P. syringae is a harmful infectious bacterium that damages plants. However, synthetic Asn-Leu-Asn-Arg did not inhibit the growth of Lactobacillus acidophilus. It is expected that this synthetic peptide would be the first peptide sequence from the bovine lactoferrin C-lobe that shows antibacterial activity.

Parasiticidal activity of bovine lactoperoxidase against Toxoplasma gondii

Toxoplasma gondii is an obligatory intracellular parasitic protozoan transmitted via the ingestion of raw, infected meat that causes congenital infections. In a cell-free environment, virulent Toxoplasma was strikingly resistant to H2O2. The activity of H2O2 or H2O2 generated by glucose – glucose oxidase against the resistant tachyzoite stage of pathogenic T. gondii was enhanced by adding KI and bovine lactoperoxidase (bLPO), referred to here as the bLPO system. Replacing bLPO (heme content, 90%) with recombinant bLPO (heme content, 6%) did not enhance the parasiticidal activity with KI and H2O2. These results indicated that heme contributed to the enzyme activity and resulted in the killing of tachyzoites of T. gondii. Tachyzoites treated with the bLPO system also lost the ability to penetrate the mouse fibroblast cell line (NIH/3T3), and could be killed intracellularly after exposure by bLPO to a mouse macrophage cell line (J774A.1). These findings suggested that toxicity was mediated through small amounts of H2O2 generated by phagocytic events in naive macrophages, and by the peroxidative activity of bLPO. Our observations suggest that the bLPO system could help prevent the development of Toxoplasmosis in humans after ingesting raw, infected meat.

Inhibitory activity of bovine milk osteopontin and its fragments on the formation of calcium phosphate precipitates

Osteopontin (OPN) is an acidic phosphorylated glycoprotein found in many tissues and physiological fluids. OPN is known to possess multiple biological functions including bone remodeling, cell adhesion, cellular transformation and immunological mediation; these functions have been extensively reviewed (Butler et al. 1996; Sodek et al. 2000).

Susceptibilities against bovine lactoferrin with microorganisms isolated from mastitic milk

Antibacterial effects of bovine lactoferrin were studied in vitro against microorganisms isolated from mastitic milk in Tokachi area, Hokkaido, Japan. Microorganisms isolated were Escherichia coli (11 isolates), Klebsiella pneumoniae (5 isolates), enterococci (8 isolates), Staphylococcus aureus (10 isolates), coagulase negative staphylococci (CNS, 13 isolates), streptococci (11 isolates), Prototheca zopfii (7 isolates) and yeast-like fungi (9 isolates). Lactoferrin has been known as a multifunctional protein and its antimicrobial effect is one of the most essential function of it. In order to compare their susceptibilities against lactoferrin, the minimal inhibitory concentration values were estimated by a microplate assay method using 96-well microplate, which involved measuring the optical density of the cultures. Prototheca zopfii was highly sensitive to bovine lactoferrin and complete inhibition of this microorganism was observed even at the low concentration of 7 mug/ml. On the other hand, E. coli and enterococci showed resistance against lactoferrin action and staphylococci showed strain-dependent resistance.

The Detection of Bovine Lactoferrin Binding Protein on Trypanosoma brucei

Trypanosoma brucei, the causative agent of sleeping sickness in humans, requires transferrin (TF) for growth. Therefore, T. brucei has a TF receptor that allows it to obtain iron from TF. Lactoferrin (LF), a member of the TF family protein, is an iron-binding protein that is found in most biological fluids of mammals. LF has been shown to interact with some bacteria species by specific receptor-ligand binding. We examined the ability of T. brucei to bind bovine LF (bLF) by using a fluorescence test, streptavidin-biotin (SAB) microplate analysis, and far Western blotting using a biotin-streptavidin system. We found that bLF bound to components of T. brucei, and that bLF hydrolysate disrupted the sites responsible for binding to parasite proteins. Furthermore, bLF, human LF, bovine TF, and ovotransferrin bound same proteins of T. brucei, which exhibited molecular masses of 40 and 43 kDa. The N-terminal amino acid sequence of the 40 kDa bLF binding protein was identified as glyceraldehyde-3-phosphate dehydrogenase (GAPDH).

Production of recombinant bovine lactoferrin N-lobe in insect cells and its antimicrobial activity

Lactoferrin is a multifunctional, iron-binding glycoprotein found in physiological fluids of mammals. In the present study, a gene encoding the N-terminal half (N-lobe) of bovine lactoferrin was cloned and expressed in cultured insect cells using a baculovirus expression system. One mutation was found in the lactoferrin N-lobe gene, but it resulted in no amino acid substitution. The recombinant lactoferrin N-lobe was secreted into the culture medium and partially purified by means of an immobilized heparin column. The recombinant lactoferrin N-lobe secreted was not glycosylated, but it possessed antimicrobial activity toward Escherichia coli O111. The recombinant product synthesized and accumulated in the host cells exhibited greater electrophoretic mobility on SDS-PAGE than the secreted product and showed no potency to inhibit the growth of bacteria. It is thought that the product accumulated intracellularly lacks antimicrobial ability due to its degradation in the host cells or due to disruption of the active conformation.