Identification of two distinct antibacterial domains within the sequence of bovine alpha(s2)-casein.
Two distinct domains with antibacterial activity were isolated from a peptic hydrolysate of bovine alpha(s2)-casein. The digested alpha(s2)-casein was fractionated by cation-exchange chromatography, after which the peptides in the two active fractions obtained were separated by high-performance liquid chromatography and sequenced by electrospray-ionization tandem mass spectrometry. The major component in each active fraction, f(183-207) and f(164-179), was further purified and the antibacterial activity of these components was tested against several microorganisms. Depending on the target bacterial strain, these peptides exhibited minimum inhibitory concentrations between 8 and 99 microM. Peptide f(183-207) exhibited a consistently higher antibacterial activity than f(164-179), although both peptides showed a comparable hemolytic effect. A method of in situ enzymatic hydrolysis on a cation-exchange membrane to obtain a fraction enriched in the most active antibacterial domain is presented. The antibacterial and hemolytic activities are discussed in relation to the structure and hydrophobicity of the peptides.
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Department of Product Technology, Section of Structure and Functionality, NIZO food research, P.O. Box 20, 6710 BA, Ede, The Netherlands.
Visser
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D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000737:chemistry*; D002364:Caseins / Q000737:chemistry*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D004912:Erythrocytes / Q000187:drug effects; D006801:Humans; D013058:Mass Spectrometry; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010434:Pepsin A; D010446:Peptide Fragments / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology
D000890:Anti-Infective Agents; D002364:Caseins; D010446:Peptide Fragments; C121342:alpha(S2)-casein (164-179); C121341:alpha(S2)-casein (183-207); D010434:Pepsin A