Positive selection of three chitinase genes of the family 18 of glycoside hydrolases in mammals |
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Authors: | Beibei He Li Wang Jinhong Wang Gang Li and Shuyi Zhang |
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Institution: | (1) School of Life Science, East China Normal University, Shanghai, 200062, People’s Republic of China;(2) College of Animal Science, Yunnan Agricultural University, Kunming, 650201, People’s Republic of China |
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Abstract: | The digestive enzyme chitinase degrades chitin, and is found in a wide range of organisms, from prokaryotes to eukaryotes.
Although mammals cannot synthesize or assimilate chitin, several proteins of the glycoside hydrolase (GH) chitinase family
GH18, including some with enzymatic activity, have recently been identified from mammalian genomes. Consequently, there is
growing interest in molecular evolution of this family of proteins. Here we report on the use of maximum likelihood methods
to test for evidence of positive selection in three genes of the chitinase family GH18, all of which are found in mammals.
These focal genes are CHIA, CHIT1 and CHI3L1, which encode the chitinase proteins acidic mammalian chitinase, chitotriosidase
and cartilage protein 39, respectively. The results of our analyses indicate that each of these genes has undergone independent
selective pressure in their evolution. Additionally, we have found evidence of a signature of positive natural selection,
with most sites identified as being subject to adaptive evolution located in the catalytic domain. Our results suggest that
positive selection on these genes stems from their function in digestion and/or immunity. |
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Keywords: | protein evolution glycoside hydrolase family GH18 chitinase positive selection |
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