Novel basic proteins, duck basic protein small 1 (dBPS 1 ) and 2 (dBPS 2 ), were isolated from duck egg white by cation-exchange and gel filtration chromatography. Protein sequence analyses indicated that they possessed 39 amino acid residues with three disulfide bonds. The amino acid sequence of dBPS 1 showed 45% identity with dBPS 2 . The amino acid sequence of dBPS 2 was the same as cygnin, a small protein from black swan, and strongly homologous with meleagrin from turkey and chicken. Phylogenic relationships implied that dBPS 1 and dBPS 2 share a common ancestry with cygnin and meleagrin. Based on MALDI-TOF mass spectra, the molecular masses of dBPS 1 and dBPS 2 were 4,373, and the 4,486 Da. pI of dBPS 1 and dBPS 2 elucidated by isoelectric focusing were 9.35 and 9.44. FT-IR spectra classified these proteins as ( ) proteins. Both dBPS 1 and dBPS 2 , possessed high heat stability, Td 101.2 and 98.3 C. Indirect ELISA results showed that the dBPS 1 /dBPS 2 -related proteins were distributed in the oviduct and gallbladder.

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The objective of the study was to investigate antimicrobial activity of native and reduced forms of duck lysozyme (dLz) against Salmonella enteritidis. Moreover, antimicrobial activity of dLz was compared with chicken lysozyme (cLz). The purified dLz was reduced with dithiothreitol. Free SH groups of reduced dLz were trapped with Combination of lactoferrin (0.1 mg/ml) and reduced dLz (0.1 mg/ml) showed a synergistic effect. In all conditions, dLz showed higher activity than cLz in both native and reduced forms. The result of the study indicated that reduced dLz trends to be a more efficient antimicrobial agent against S. enteritidis. To achieve the highest sufficiency, the essential roles of food components and incubation temperature should be concerned in reduced dLz application.

Biological functions of duck basic protein small 1 (dBPS(1)) and 2 (dBPS(2)) were investigated by in vitro experiments. Results of agarose gel retardation assay indicated that dBPS(1) and dBPS(2) associate with RNA. Addition of NaCl or urea induced partial dissociation of dBPS(1)/dBPS(2)-RNA complex, implying that electrostatic interaction, hydrophobic interaction, and hydrogen bonds are involved in the association of dBPS(1)/dBPS(2) to RNA. dBPS(1) and dBPS(2) inhibited pancreatic lipase activity with the fifty percent inhibitory concentration (IC(50)) of 250 and 100 μg/mL, respectively. Peptic hydrolysates of dBPS(1) and those of dBPS(2) showed a potent angiotensin I-converting enzyme (ACE) inhibition with an IC(50) of 22.5 and 49.6 mg/L. The most potent ACE-inhibitory peptide was a nanopeptide (EKKGFCAGY) from dBPS(1) and an octapeptide (KYCPKVGY) from dBPS(2). These multiple biological functions of dBPS(1) and dBPS(2) may contribute to reducing the risk of lifestyle diseases.

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