1. Kappacin, a novel antibacterial peptide from bovine milk.
- Author
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Malkoski M, Dashper SG, O'Brien-Simpson NM, Talbo GH, Macris M, Cross KJ, and Reynolds EC
- Subjects
- Animals, Anti-Bacterial Agents isolation & purification, Caseins isolation & purification, Cattle, Chromatography, High Pressure Liquid, Colony Count, Microbial, Escherichia coli growth & development, Mass Spectrometry, Peptide Fragments isolation & purification, Phosphorylation, Porphyromonas gingivalis growth & development, Streptococcus mutans genetics, Anti-Bacterial Agents pharmacology, Caseins pharmacology, Escherichia coli drug effects, Milk chemistry, Peptide Fragments pharmacology, Porphyromonas gingivalis drug effects, Streptococcus mutans drug effects
- Abstract
Caseinomacropeptide (CMP) is a heterogeneous C-terminal fragment (residues 106 to 169) of bovine milk kappa-casein composed of glycosylated and phosphorylated forms of different genetic variants. We have demonstrated that CMP has growth-inhibitory activity against the oral opportunistic pathogens Streptococcus mutans and Porphyromonas gingivalis and against Escherichia coli. CMP was fractionated using reversed-phase high-performance liquid chromatography (RP-HPLC), and each fraction was tested for activity against S. mutans in a 96-well-plate broth assay. Fractions were characterized by N-terminal sequence analysis and mass spectrometry. The active form of CMP was shown to be the nonglycosylated, phosphorylated kappa-casein (residues 106 to 169) [kappa-casein(106--169)], which we have designated kappacin. Endoproteinase Glu-C was used to hydrolyze CMP, and the generated peptides were separated using RP-HPLC and gel filtration-HPLC and then tested for activity against S. mutans. The peptide Ser(P)(149)kappa-casein-A(138--158) was the only peptide generated by endoproteinase Glu-C digestion that exhibited growth-inhibitory activity. Peptides corresponding to the sequences of the inhibitory peptide Ser(P)(149)kappa-casein-A(138--158) and its nonphosphorylated counterpart kappa-casein-A(138--158) were chemically synthesized and tested for antibacterial activity. The synthetic Ser(P)(149) kappa-casein-A(138--158) displayed growth-inhibitory activity against S. mutans (MIC, 59 microg/ml [26 microM]). The nonphosphorylated peptide, however, did not inhibit growth at the concentrations tested, indicating that phosphorylation is essential for activity.
- Published
- 2001
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