Isozymes of lysozyme in leukocytes and egg white: evidence for the species-specific control of egg-white lysozyme synthesis.

Two structurally distinct forms of eggwhite lysozyme (EC 3.2.1.17) are known. The egg white of some species contains both of these forms, while the egg white of other species appears to contain only one or the other of them. We have immunological and electrophoretic evidence that the chicken, which has only one lysozyme type in its egg white, contains both types in its polymorphonuclear leukocytes. Experiments on Embden goose bone marrow showed that this tissue also contains both lysozymes, even though the egg white of this species contains only one of them. Our studies suggest that many avian species have the genetic loci that code for both forms of lysozyme, but that a species-specific regulatory mechanism controls whether one or the other or both of them are expressed during egg white production. The fact that two distinct lysozymes are present in chicken leukocytes may be of significance to the antibacterial mechanism of these cells, especially in light of the fact that they lack myeloperoxidase, an important leukocyte enzyme in mammals.