title: Loss and Gain of Human Acidic Mammalian Chitinase Activity by Nonsynonymous SNPs.
abstract: Acidic mammalian chitinase (AMCase) is implicated in asthma, allergic inflammation, and food processing. Little is known about genetic and evolutional regulation of chitinolytic activity of AMCase. Here, we relate human AMCase polymorphisms to the mouse AMCase, and show that the highly active variants encoded by nonsynonymous single-nucleotide polymorphisms (nsSNPs) are consistent with the mouse AMCase sequence. The chitinolytic activity of the recombinant human AMCase was significantly lower than that of the mouse counterpart. By creating mouse-human chimeric AMCase protein we found that the presence of the N-terminal region of human AMCase containing conserved active site residues reduced the enzymatic activity of the molecule. We were able to significantly increase the activity of human AMCase by amino acid substitutions encoded by nsSNPs (N45, D47, and R61) with those conserved in the mouse homologue (D45, N47, and M61). For abolition of the mouse AMCase activity, introduction of M61R mutation was sufficient. M61 is conserved in most of primates other than human and orangutan as well as in other mammals. Orangutan has I61 substitution, which also markedly reduced the activity of the mouse AMCase, indicating that the M61 is a crucial residue for the chitinolytic activity. Altogether, our data suggest that human AMCase has lost its chitinolytic activity by integration of nsSNPs during evolution and that the enzyme can be reactivated by introducing amino acids conserved in the mouse counterpart.
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Okawa
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Misa
authors.initials: M
authors.lastname: Ohno
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Kashimura
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kimura
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Sakaguchi
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Yasusato
authors.initials: Y
authors.lastname: Sugahara
authors.affiliation: Department of Applied Chemistry, Kogakuin University, Hachioji, Tokyo, Japan.
authors.forename: Minori
authors.initials: M
authors.lastname: Kamaya
authors.affiliation: Department of Bioinformatics and Molecular Neuropathology, Meiji Pharmaceutical University, Kiyose, Tokyo, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kino
authors.affiliation: Department of Neuroscience, Mayo Clinic, Jacksonville, FL.
authors.forename: Peter O
authors.initials: PO
authors.lastname: Bauer
authors.affiliation: Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo, Japan f-oyama@cc.kogakuin.ac.jp.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Oyama
mesh_terms: D000818:Animals; D001249:Asthma / Q000201:enzymology / Q000235:genetics; D002688:Chitinases / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D020641:Polymorphism, Single Nucleotide
chemical_list: C499255:AMCase, mouse; C499254:CHIA protein, human; D002688:Chitinases
keywords: acidic mammalian chitinase; amino acid substitutions; chitinolytic activity; pseudogene; reactivation; single-nucleotide polymorphisms