State Key Laboratory of Fine Chemical Engineering, School of Life Science and Biotechnology and School of Software, Dalian University of Technology, No. 2 Linggong Road, Dalian, Liaoning 116024, People's Republic of China.
Acta Crystallogr D Struct Biol. 2018 Jan 1;74(Pt 1):30-40. doi: 10.1107/S2059798317018289.
The glycoside hydrolase family 18 chitinases degrade or alter chitin. Multiple catalytic domains in a glycoside hydrolase family 18 chitinase function synergistically during chitin degradation. Here, an insect group III chitinase from the agricultural pest Ostrinia furnacalis (OfChtIII) is revealed to be an arthropod-conserved chitinase that contains two nonsynergistic GH18 domains according to its catalytic properties. Both GH18 domains are active towards single-chained chitin substrates, but are inactive towards insoluble chitin substrates. The crystal structures of each unbound GH18 domain, as well as of GH18 domains complexed with hexa-N-acetyl-chitohexaose or penta-N-acetyl-chitopentaose, suggest that the two GH18 domains possess endo-specific activities. Physiological data indicated that the developmental stage-dependent gene-expression pattern of OfChtIII was the same as that of the chitin synthase OfChsA but significantly different from that of the chitinase OfChtI, which is indispensable for cuticular chitin degradation. Additionally, immunological staining indicated that OfChtIII was co-localized with OfChsA. Thus, OfChtIII is most likely to be involved in the chitin-synthesis pathway.
糖苷水解酶家族 18 几丁质酶降解或改变几丁质。在几丁质降解过程中，糖苷水解酶家族 18 几丁质酶中的多个催化结构域协同作用。本文揭示了一种来自农业害虫烟夜蛾（Ostrinia furnacalis）的昆虫组 III 几丁质酶（OfChtIII）是一种节肢动物保守的几丁质酶，根据其催化特性，它包含两个非协同的 GH18 结构域。这两个 GH18 结构域都对单链几丁质底物具有活性，但对不溶性几丁质底物没有活性。每个未结合的 GH18 结构域的晶体结构，以及与六-N-乙酰壳六糖或五-N-乙酰壳五糖复合的 GH18 结构域的晶体结构，表明这两个 GH18 结构域具有内切特异性活性。生理数据表明，OfChtIII 的发育阶段依赖性基因表达模式与几丁质合酶 OfChsA 相同，但与几丁质酶 OfChtI 显著不同，后者对于表皮几丁质降解是不可或缺的。此外，免疫染色表明 OfChtIII 与 OfChsA 共定位。因此，OfChtIII 很可能参与几丁质合成途径。
