Multiple Lysozymes of Duck Egg White

Lysozyme was purified from a pooled sample of Peking duck egg whites by ion exchange chromatography and gel filtration. Three different lysozymes were found, and each was shown to be pure by several criteria. The three enzymes were like chicken lysozyme in molecular size and specific activity, although they could be distinguished from it, as well as from one another, by electrophoretic and immunological criteria. The three duck enzymes were shown to be very similar to one another on the basis of amino acid composition (in particular, all lacked histidine) and immunological tests. Lysozyme was then partially purified from 44 individual duck egg whites and subjected to starch gel electrophoresis at pH 5.3, at which the three different lysozymes are readily distinguishable from each other. Each individual egg white contained either any one of the three lysozymes alone or a combination of any two of them. No single egg white contained all three duck lysozymes. The frequency of the six different phenotypes, as well as the marked similarity of the three enzymes to one another, leads us to suggest the existence of three alleles at one locus in the duck population which we examined.