Research Title

Research Area：Biochemistry

Acidic mammalian chitinase is a proteasesresistant glycosidase in mouse digestive system
Misa Ohno and Fumitaka Oyama, Department of Chemistry and Life Science
Keywords： acidic mammalian chitinase, chitin, digestive enzyme, gastrointestinal environments,
protease resistant glycosidase
Chitinases are enzymes that hydrolyze chitin, a polymer of β-1, 4-linked N-acetyl-DOutline
glucosamine (GlcNAc). Chitin is the second most abundant naturally occurring polysaccharide.
Since it has been thought to be not degraded in the digestive system, it has been considereddietary fiber. In this study, we provide evidence that acidic mammalian chitinase (AMCase) canfunction as a major digestive enzyme that constitutively degrades chitin substrates andproduces (GlcNAc)2 fragments in the mouse gastrointestinal environment. AMCase wasresistant to endogenous pepsin C digestion and remained active in the mouse stomach extractat pH 2.0 (Fig. 1). The AMCase mRNA levels were much higher than those of four major
gastric proteins and comparable to the level of pepsinogen C in the mouse stomach tissues(Fig.2a). Furthermore, AMCase was expressed in the gastric pepsinogen-synthesizing chiefcells (Fig.2b). The enzyme was also stable and active in the presence of trypsin andchymotrypsin at pH 7.6, where pepsin C was completely degraded (Fig.3). Mouse AMCase
degraded polymeric chitin substrates in the gastrointestinal environments in presence of theproteolytic enzymes (Fig.4).

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関連論文

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Fig.1. Soluble proteins obtained from mouse stomach wereincubated at 37°C for 0, 5, 10, 20, 40 and 60 min at pH 7.6 or
2.0. (a) Western blot, (b) chitinolytic activity.

aabFig. 3. Soluble proteins fraction from mouse stomach wasincubated at pH 2.0, followed by at pH 7.6 containing trypsin
and chymotrypsin. (a) Western blot and (b) chitinolytic activity.

aFig. 2. (a) The mRNA levels of nine genes were quantified by
qPCR. (b) Expression and co-localization of pepsin C (green)and AMCase (red) proteins in mouse stomach sections
shown by immunohistochemistry.

bFig. 4. Degradation products were generated during incubationof colloidal (a) and crystalline chitin (b) with the extract of mousestomach at pH 2.0 for 1 hour and subsequently at pH 7.6 for 3
hours after addition of equal amount of trypsin and chymotrypsin.

Novelty

Our results clearly show that AMCase is able to digest chitin polymers even in the presenceof pepsin C, trypsin and chymotrypsin. The main degradation product, (GlcNAc)2, can bethen uptaken in mouse GIT, providing the primary source of carbon, nitrogen and energy.

Application

Chitin can be used in feeds for murine breeding.

●Original paper Ohno, M., Kimura, M., Miyazaki,H., Okawa, K., Onuki, R., Nemoto, C., Tabata, E., Wakita, S.,
RelatedKashimura, A., Sakaguchi, M., Sugahara, Y., Nukina, N., Bauer, PO. and Oyama, F. (2016)
information●URL

Acidic mammalian chitinase is a proteases-resistant glycosidase in mouse digestive system.
Sci. Rep. 6, 37756.
http://www.nature.com/articles/srep37756

The Research Promotion Section, The Research Institute of Science and Technology,
Kogakuin University, Hachioji, Tokyo, Japan
E-Mail: souken@sc.kogakuin.ac.jp URL:http://www.kogakuin.ac.jp/english/