Lysozymes in the animal kingdom.
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2010-03
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Abstract
Lysozymes (EC 3.2.1.17) are hydrolytic enzymes, characterized by their ability to cleave the β-(1,4)-glycosidic bond
between N-acetylmuramic acid and N-acetylglucosamine in peptidoglycan, the major bacterial cell wall polymer. In
the animal kingdom, three major distinct lysozyme types have been identifi ed – the c-type (chicken or conventional
type), the g-type (goose-type) and the i-type (invertebrate type) lysozyme. Examination of the phylogenetic distribution
of these lysozymes reveals that c-type lysozymes are predominantly present in the phylum of the Chordata and in
different classes of the Arthropoda. Moreover, g-type lysozymes (or at least their corresponding genes) are found in
members of the Chordata, as well as in some bivalve mollusks belonging to the invertebrates. In general, the latter
animals are known to produce i-type lysozymes. Although the homology in primary structure for representatives of
these three lysozyme types is limited, their three-dimensional structures show striking similarities. Nevertheless, some
variation exists in their catalytic mechanisms and the genomic organization of their genes. Regarding their biological
role, the widely recognized function of lysozymes is their contribution to antibacterial defence but, additionally, some
lysozymes (belonging to different types) are known to function as digestive enzymes.
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Callewaert Lien, Michiels Chris W. Lysozymes in the animal kingdom. Journal of Biosciences. 2010 Mar; 35(1): 127-160.