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Updated: Dec 10, 2025
Measurement of Chitinase Activity in Biological Samples
Published on: August 22, 2019
Comparative functional analysis between human and mouse chitotriosidase: Substitution at amino acid 218 modulates the
Masahiro Kimura1, Takashi Watanabe2, Kazutaka Sekine2
1Department of Chemistry and Life Science, Kogakuin University, Hachioji, Tokyo 192-0015, Japan; Research Fellow of Japan Society for the Promotion of Science (PD), Koujimachi, Chiyoda-ku, Tokyo 102-0083, Japan; Laboratory for Immunopharmacology of Microbial Products, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan.
Abstract:
Chitotriosidase (Chit1) and acidic mammalian chitinase (AMCase) have been attracting research interest due to their involvement in various pathological conditions such as Gaucher's disease and asthma, respectively. Both enzymes are highly expressed in mice, while the level of AMCase mRNA was low in human tissues. In addition, the chitinolytic activity of the recombinant human AMCase was significantly lower than that of the mouse counterpart. Here, we revealed a substantially higher chitinolytic and transglycosylation activity of human Chit1 against artificial and natural chitin substrates as compared to the mouse enzyme. We found that the substitution of leucine (L) by tryptophan (W) at position 218 markedly reduced both activities in human Chit1. Conversely, the L218W substitution in mouse Chit1 increased the activity of the enzyme. These results suggest that Chit1 may compensate for the low of AMCase activity in humans, while in mice, highly active AMCase may supplements low Chit1 activity.
Insights
Human chitotriosidase (Chit1) shows higher activity than mouse Chit1, compensating for lower human acidic mammalian chitinase (AMCase) levels. Enzyme activity is influenced by specific amino acid substitutions, highlighting species-specific functional roles.
Area of Science:
- Biochemistry
- Enzymology
- Comparative Genomics
Background:
- Chitotriosidase (Chit1) and acidic mammalian chitinase (AMCase) are implicated in diseases like Gaucher's disease and asthma.
- AMCase mRNA levels are low in human tissues, and its activity is lower than in mice.
- Both enzymes are highly expressed in mice, suggesting species-specific functional differences.
Purpose of the Study:
- To compare the chitinolytic and transglycosylation activities of human and mouse Chit1.
- To investigate the impact of specific amino acid substitutions on enzyme activity.
- To understand the compensatory roles of Chit1 and AMCase in humans and mice.
Main Methods:
- Enzyme activity assays using artificial and natural chitin substrates.
- Site-directed mutagenesis to introduce specific amino acid substitutions (L218W).
- Comparison of recombinant human and mouse enzyme activities.
Main Results:
- Human Chit1 exhibited significantly higher chitinolytic and transglycosylation activity than mouse Chit1.
- The L218W substitution reduced activity in human Chit1 but increased activity in mouse Chit1.
- Human AMCase showed lower chitinolytic activity compared to its mouse counterpart.
Conclusions:
- Human Chit1 may compensate for the lower activity of AMCase in humans.
- Highly active mouse AMCase may supplement the lower activity of mouse Chit1.
- Specific amino acid residues play a critical role in the differential activity of Chit1 between species.
