Dixit Radhika, Arakane Yasuyuki, Specht Charles A, Richard Chad, Kramer Karl J, Beeman Richard W, Muthukrishnan Subbaratnam
Department of Biochemistry, Kansas State University, Manhattan, KS 66506, USA.
Insect Biochem Mol Biol. 2008 Apr;38(4):440-51. doi: 10.1016/j.ibmb.2007.12.002. Epub 2007 Dec 14.
A bioinformatics investigation of four insect species with annotated genome sequences identified a family of genes encoding chitin deacetylase (CDA)-like proteins, with five to nine members depending on the species. CDAs (EC 3.5.1.41) are chitin-modifying enzymes that deacetylate the beta-1,4-linked N-acetylglucosamine homopolymer. Partial deacetylation forms a heteropolysaccharide that also contains some glucosamine residues, while complete deacetylation produces the homopolymer chitosan, consisting exclusively of glucosamine. The genomes of the red flour beetle, Tribolium castaneum, the fruit fly, Drosophila melanogaster, the malaria mosquito, Anopheles gambiae, and the honey bee, Apis mellifera contain 9, 6, 5 and 5 genes, respectively, that encode proteins with a chitin deacetylase motif. The presence of alternative exons in two of the genes, TcCDA2 and TcCDA5, increases the protein diversity further. Insect CDA-like proteins were classified into five orthologous groups based on phylogenetic analysis and the presence of additional motifs. Group I enzymes include CDA1 and isoforms of CDA2, each containing in addition to a polysaccharide deacetylase-like catalytic domain, a chitin-binding peritrophin-A domain (ChBD) and a low-density lipoprotein receptor class A domain (LDLa). Group II is composed of CDA3 orthologs from each insect species with the same domain organization as group I CDAs, but differing substantially in sequence. Group III includes CDA4s, which have the ChBD domain but do not have the LDLa domain. Group IV comprises CDA5s, which are the largest CDAs because of a very long intervening region separating the ChBD and catalytic domains. Among the four insect species, Tribolium is unique in having four CDA genes in group V, whereas the other insect genomes have either one or none. Most of the CDA-like proteins have a putative signal peptide consistent with their role in modifying extracellular chitin in both cuticle and peritrophic membrane during morphogenesis and molting.
一项对四种具有注释基因组序列的昆虫物种的生物信息学研究，鉴定出了一个编码几丁质脱乙酰酶（CDA）样蛋白的基因家族，根据物种不同，该家族有5至9个成员。CDA（EC 3.5.1.41）是一种几丁质修饰酶，可使β-1,4-连接的N-乙酰葡糖胺同聚物脱乙酰化。部分脱乙酰化形成一种杂多糖，其中也含有一些葡糖胺残基，而完全脱乙酰化则产生仅由葡糖胺组成的同聚物壳聚糖。赤拟谷盗（Tribolium castaneum）、果蝇（Drosophila melanogaster）、冈比亚按蚊（Anopheles gambiae）和蜜蜂（Apis mellifera）的基因组分别包含9个、6个、5个和5个编码具有几丁质脱乙酰酶基序蛋白的基因。TcCDA2和TcCDA5这两个基因中存在可变外显子，进一步增加了蛋白质的多样性。基于系统发育分析和其他基序的存在，昆虫CDA样蛋白被分为五个直系同源组。第一组酶包括CDA1和CDA2的同工型，除了一个多糖脱乙酰酶样催化结构域外，每个还含有一个几丁质结合的围食膜蛋白-A结构域（ChBD）和一个低密度脂蛋白受体A类结构域（LDLa）。第二组由来自每种昆虫物种的CDA3直系同源物组成，其结构域组织与第一组CDA相同，但序列差异很大。第三组包括CDA4，其具有ChBD结构域但没有LDLa结构域。第四组由CDA5组成，由于ChBD和催化结构域之间有很长的间隔区域，它们是最大的CDA。在这四种昆虫物种中，拟谷盗在第五组中有四个CDA基因，这一点很独特，而其他昆虫基因组要么有一个，要么没有。大多数CDA样蛋白都有一个推定的信号肽，这与它们在形态发生和蜕皮过程中修饰表皮和围食膜中的细胞外几丁质的作用一致。
