Evolution of Mammalian Chitinase(-Like) Members of Family 18 Glycosyl Hydrolases

Family 18 of glycosyl hydrolases encompasses chitinases and so-called chi-lectins lacking enzymatic activity due to amino acid substitutions in their active site. Both types of proteins widely occur in mammals although these organisms lack endogenous chitin. Their physiological function(s) as well a...

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Bibliographic Details
Published in:Genetics (Austin) 2007-10, Vol.177 (2), p.959-970
Main Authors: Bussink, Anton P, Speijer, Dave, Aerts, Johannes M. F. G, Boot, Rolf G
Format: Article
Language:English
Subjects:
Animals
Chitinases - genetics
Crystal structure
Enzymes
Evolution, Molecular
Gene Duplication
Genes
Genetics
Glycoside Hydrolases - genetics
Hexosaminidases - genetics
Investigations
Lectins - genetics
Mammals
Mutation
Phylogeny
Proteins
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Summary:Family 18 of glycosyl hydrolases encompasses chitinases and so-called chi-lectins lacking enzymatic activity due to amino acid substitutions in their active site. Both types of proteins widely occur in mammals although these organisms lack endogenous chitin. Their physiological function(s) as well as evolutionary relationships are still largely enigmatic. An overview of all family members is presented and their relationships are described. Molecular phylogenetic analyses suggest that both active chitinases (chitotriosidase and AMCase) result from an early gene duplication event. Further duplication events, followed by mutations leading to loss of chitinase activity, allowed evolution of the chi-lectins. The homologous genes encoding chitinase(-like) proteins are clustered in two distinct loci that display a high degree of synteny among mammals. Despite the shared chromosomal location and high homology, individual genes have evolved independently. Orthologs are more closely related than paralogues, and calculated substitution rate ratios indicate that protein-coding sequences underwent purifying selection. Substantial gene specialization has occurred in time, allowing for tissue-specific expression of pH optimized chitinases and chi-lectins. Finally, several family 18 chitinase-like proteins are present only in certain lineages of mammals, exemplifying recent evolutionary events in the chitinase protein family.
ISSN:0016-6731
1943-2631
1943-2631
DOI:10.1534/genetics.107.075846