New variant of quail egg white lysozyme identified by peptide mapping

Two lysozymes were purified from quail egg white by cation exchange column chromatography and analyzed for amino acid sequence. The enzymes showed the same pH optimum profile for lytic activity with broad pH optima (pH 5.0-8.0) but had difference in mobility on native-PAGE. The native-PAGE immunoblot showed one or two lysozymes present in individual egg whites. The established amino acid sequence of quail egg white lysozyme A (QEWL A) was the same as quail lysozyme reported by Kaneda et al. [Kaneda, M., Kato, I., Tominaga, N., Titani, K., Narita, K., 1969. The amino acid sequence of quail lysozyme. J. Biochem. (Tokyo). 66, 747-749] and had six amino acid substitutions at position 3 (Phe to Tyr), 19 (Asn to Lys), 21 (Arg to Gln), 102 (Gly to Val) 103 (Asn to His) and 121 (Gln to Asn) compared to hen egg white lysozyme. QEWL A and QEWL B showed one substitution, at the position 21, Gln replaced by Lys, plus an insertion of Leu between position 20 and 21, being the first report that QEWL B had 130 amino acids. The amino acid differences between two lysozymes did not seem to affect antigenic determinants detected by polyclonal anti-hen egg white lysozyme, but caused them to separate well from each other by ion exchange chromatography.