Boot R G, Blommaart E F, Swart E, Ghauharali-van der Vlugt K, Bijl N, Moe C, Place A, Aerts J M
Department of Biochemistry, University of Amsterdam, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands.
J Biol Chem. 2001 Mar 2;276(9):6770-8. doi: 10.1074/jbc.M009886200. Epub 2000 Nov 20.
Chitinases are ubiquitous chitin-fragmenting hydrolases. Recently we discovered the first human chitinase, named chitotriosidase, that is specifically expressed by phagocytes. We here report the identification, purification, and subsequent cloning of a second mammalian chitinase. This enzyme is characterized by an acidic isoelectric point and therefore named acidic mammalian chitinase (AMCase). In rodents and man the enzyme is relatively abundant in the gastrointestinal tract and is found to a lesser extent in the lung. Like chitotriosidase, AMCase is synthesized as a 50-kDa protein containing a 39-kDa N-terminal catalytic domain, a hinge region, and a C-terminal chitin-binding domain. In contrast to chitotriosidase, the enzyme is extremely acid stable and shows a distinct second pH optimum around pH 2. AMCase is capable of cleaving artificial chitin-like substrates as well as crab shell chitin and chitin as present in the fungal cell wall. Our study has revealed the existence of a chitinolytic enzyme in the gastrointestinal tract and lung that may play a role in digestion and/or defense.
几丁质酶是普遍存在的可分解几丁质的水解酶。最近我们发现了首个人类几丁质酶，命名为壳三糖酶，它由吞噬细胞特异性表达。我们在此报告第二种哺乳动物几丁质酶的鉴定、纯化及后续克隆。这种酶的特征是酸性等电点，因此命名为酸性哺乳动物几丁质酶（AMCase）。在啮齿动物和人类中，该酶在胃肠道中相对丰富，在肺中含量较少。与壳三糖酶一样，AMCase最初合成时是一种50 kDa的蛋白质，包含一个39 kDa的N端催化结构域、一个铰链区和一个C端几丁质结合结构域。与壳三糖酶不同的是，该酶在酸性条件下极其稳定，在pH 2左右有明显的第二个最适pH值。AMCase能够切割人工合成的几丁质样底物以及蟹壳几丁质和真菌细胞壁中的几丁质。我们的研究揭示了胃肠道和肺中存在一种可能在消化和/或防御中起作用的几丁质分解酶。
