The BmChi-h gene, a bacterial-type chitinase gene of Bombyx mori, encodes a functional exochitinase that plays a role in the chitin degradation during the molting process
The BmChi-h gene, a bacterial-type chitinase gene of Bombyx mori, encodes a functional exochitinase that plays a role in the chitin degradation during the molting process
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DOI：
10.1016/j.ibmb.2005.05.005
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发表时间：
2005-10-01
影响因子：
3.8
通讯作者：
Shimada, T
中科院分区：
文献类型：
--
作者：
Daimon, T;Katsuma, S;Shimada, T
家蚕除了含有一个几丁质内切酶基因（BmChitinase）外，还含有一个细菌型几丁质酶基因（BmChi-h）。BmChi-h的氨基酸序列与粘质沙雷氏菌（Serratia marcescens chiA）和杆状病毒（baculoviruses，v-CHIA）的几丁质酶具有广泛的结构相似性。细菌型几丁质酶基因除鳞翅目昆虫和鳞翅目杆状病毒外，尚未在任何真核生物和病毒中发现。因此，这表明BmChi-h可以通过水平基因转移从细菌或杆状病毒几丁质酶基因衍生。本研究对BmChi-h的生物学功能进行了初步研究。酶学性质研究表明，BmChi-h编码的几丁质酶与S. marcescens chiA和v-CHIA，与BmChitinase具有内切型底物选择性不同。免疫组织化学研究表明，BmChi-h定位于蜕皮阶段的几丁质组织中，表明它在蜕皮过程中几丁质降解中起作用。这些结果表明，BmChi-h（外切几丁质酶）和BmChitinase（内切几丁质酶）可能通过协同机制催化天然几丁质。BmChi-h同源基因的克隆和比较表明，细菌型几丁质酶基因在鳞翅目昆虫中高度保守，这表明细菌型几丁质酶在蜕皮过程中的利用可能是鳞翅目昆虫的一个普遍特征。(c)2005爱思唯尔有限公司保留所有权利。
The silkworm, Bombyx mori, has been recently demonstrated to contain a bacterial-type chitinase gene (BmChi-h) in addition to a well-characterized endochitinase gene (BmChitinase). The deduced amino acid sequence of BmChi-h showed extensive structural similarities with chitinases from bacteria such as Serratia marcescens chiA and baculoviruses (v-CHIA). Bacterial-type chitinase genes have not been found from any eukaryotes and viruses except for lepidopteran insects and lepidopteran baculoviruses. Thus, it was suggested that BmChi-h may be derived from a bacterial or baculovirus chitinase gene via horizontal gene transfer. In this report, we investigated the biological function of BmChi-h. Our enzymological study indicated that a chitinase encoded by BmChi-h has exo-type substrate preference, which is the same as S. marcescens chiA and v-CHIA, and different from BmChitinase, which has endo-type substrate preference. An immunohistochemical study revealed that BmChi-h localizes in the chitin-containing tissues during the molting stages, indicating that it plays a role in chitin degradation during molting. These results suggest that BmChi-h (exochitinase) and BmChitinase (endochitinase) may catalyze a native chitin by a concerted mechanism. Cloning and comparison of BmChi-h orthologues revealed that bacterial-type chitinase genes are highly conserved among lepidopteran insects, suggesting that the utilization of a bacterial-type chitinase during the molting process may be a general feature of lepidopteran insects. (c) 2005 Elsevier Ltd. All rights reserved.