Open Access Open Badges Research article

Evolution of the mammalian lysozyme gene family

David M Irwin12*, Jason M Biegel3 and Caro-Beth Stewart3

Author affiliations

1 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada

2 Banting and Best Diabetes Centre, University of Toronto, Toronto, Canada

3 Department of Biological Sciences, University at Albany, State University of New York, Albany, New York 12222, USA

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Citation and License

BMC Evolutionary Biology 2011, 11:166  doi:10.1186/1471-2148-11-166

Published: 15 June 2011



Lysozyme c (chicken-type lysozyme) has an important role in host defense, and has been extensively studied as a model in molecular biology, enzymology, protein chemistry, and crystallography. Traditionally, lysozyme c has been considered to be part of a small family that includes genes for two other proteins, lactalbumin, which is found only in mammals, and calcium-binding lysozyme, which is found in only a few species of birds and mammals. More recently, additional testes-expressed members of this family have been identified in human and mouse, suggesting that the mammalian lysozyme gene family is larger than previously known.


Here we characterize the extent and diversity of the lysozyme gene family in the genomes of phylogenetically diverse mammals, and show that this family contains at least eight different genes that likely duplicated prior to the diversification of extant mammals. These duplicated genes have largely been maintained, both in intron-exon structure and in genomic context, throughout mammalian evolution.


The mammalian lysozyme gene family is much larger than previously appreciated and consists of at least eight distinct genes scattered around the genome. Since the lysozyme c and lactalbumin proteins have acquired very different functions during evolution, it is likely that many of the other members of the lysozyme-like family will also have diverse and unexpected biological properties.