Effect of trypsin on bovine lactoferrin and interaction between the fragments under different conditions

Characterization of proteolytic degradation products of vaginally administered bovine lactoferrin

When bovine lactoferrin (bLF) contacts human vaginal fluid (VF) it is subjected to proteolytic degradation. This report describes fragmentation patterns of bLF dosed vaginally in clinical trials or incubated ex vivo with VF. A consensus pattern of fragments was observed in samples from different women. The 80 kDa bLF molecule is initially cleaved between its homologous 40 kDa domains, the N-lobe and C-lobe, and then degraded into sub-fragments and mixtures of small peptides. We characterized this fragmentation process by polyacrylamide gel electrophoresis, western blotting, chromatographic separation, and mass spectral sequence analysis. Common to most VF fragmentation patterns were large amounts of an N-lobe 37 kDa fragment and a C-lobe 43 kDa fragment resulting from a single cleavage following tyrosine 324. Both fragments possessed full sets of iron-ligand amino acids and retained iron-binding ability. In some VF samples, alternative forms of large fragments were found, which like the 37+43 kDa pair, totaled 80 kDa. These included 58+22 kDa, 18+62 kDa, and 16+64 kDa forms. In general, the smaller component was from the N-lobe and the larger from the C-lobe. The 18+62 kDa pair was absent in some VF samples but highly abundant in others. This variability suggests multiple endopeptidases are involved, with the 18 kDa fragment’s presence dependent upon the balance of enzymes. Further action of VF endopeptidases produced smaller peptide fragments, and we found evidence that exopeptidases trimmed their N- and C-termini. The 3.1 kDa antimicrobial peptide lactoferricin B was not detected. These studies were facilitated by a novel technique we developed: tricolor western blots, which enabled simultaneous visualization of N- and C-terminal epitopes.

Effect of bovine lactoferrin addition to milk in yogurt manufacturing

The aim of this work was to study the effect of milk supplementation with lactoferrin of different iron saturation on the manufacturing and characteristics of yogurt. Bovine lactoferrin was added at concentrations of 0.5, 1, and 2 mg/mL in the holo (iron saturated) and apo (without iron) forms. Some physicochemical properties, such as pH, concentration of lactic acid, and texture of supplemented yogurts, were determined throughout the shelf-life period storage (28 d) at 4°C. We also evaluated the stability of lactoferrin in supplemented yogurt throughout the storage time. The supplementation of milk with bovine lactoferrin did not greatly affect the physical properties of the yogurt, though apo-lactoferrin slightly delayed the decrease of pH. This could be attributed to the partial inhibition observed on the growth of Streptococcus thermophilus. The integrity and immunoreactive concentration of lactoferrin, determined by Western blotting and noncompetitive ELISA, respectively, remained constant throughout the shelf life of yogurt.

Peptides generated from milk proteins in the bovine mammary gland during involution

Proteolytic activity in mammary gland secretions is associated with hydrolysis of secretory proteins during involution. Peptides generated from hydrolysis of milk proteins were characterized in secretions from the bovine mammary gland during involution to understand the fate of the milk proteins better. Mass spectral analysis of mammary secretions showed numerous peptides ranging between 0.7 and 14 kDa during mammary involution, but these peptides were not observed in normal milk. Mass spectral profiles representing discrete peptide fragments were similar on d 7, 14, and 21 of involution, suggesting that milk proteins were only partially hydrolyzed during involution. N-Terminal amino acid sequences of four peptides indicated that they were produced by hydrolysis of beta-casein during involution and probably resulted from plasmin hydrolysis. A 20-kDa peptide was identified as a fragment of a 39-kDa protein that was previously identified in bovine mammary secretions during involution. Mass spectral analysis of lactoferrin isolated from mammary secretions during involution showed major hydrolytic products. Immunoblot analysis confirmed that lactoferrin that was isolated from mammary secretions during involution contained a number of hydrolytic products. Intramammary hydrolysis of milk proteins by plasmin probably leads to the generation of the discrete peptides observed in the mammary secretions and contributes to the fate of these proteins during involution of the bovine mammary gland.

Proteolysis of milk proteins during involution of the bovine mammary gland

The role of proteolytic hydrolysis of milk proteins in the mammary gland during involution is unknown. The objectives of this study were to determine the activities of plasmin, plasminogen, and plasminogen activator in mammary gland secretions collected during involution and to identify peptides generated by proteolysis of casein and lactoferrin in those secretions. Mammary secretions were collected from Holstein cows on d 7, 14, and 21 of involution and on d 7 postcalving. Activities of plasmin, plasminogen, and plasminogen activator were determined on the defatted, filtered aqueous phase of mammary secretions. Activities of plasmin, plasminogen, and plasminogen activator were significantly higher on d 7, 14, and 21 of involution than were those on d 7 postcalving. Protein fragments resulting from hydrolysis were detected by SDS-PAGE in samples collected on d 7, 14, and 21 of involution, but few protein fragments were observed in samples collected on d 7 postcalving when plasmin activity was low. Immunoblot analysis showed that a number of peptides observed during involution were generated from alpha s-casein (CN), beta-CN, kappa-CN, or lactoferrin. The appearance of peptides from proteins of mammary secretions during early involution was generally correlated with increased plasmin activity. Elevated plasmin activity during mammary involution may be primarily responsible for the observed concurrent hydrolysis of milk proteins in mammary secretions.