Identification and characterization of β-D-galactofuranosidases from Aspergillus nidulans and Aspergillus fumigatus
Identification and characterization of β-D-galactofuranosidases from Aspergillus nidulans and Aspergillus fumigatus
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DOI：
10.1016/j.jbiosc.2020.09.006
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发表时间：
2021-01-01
影响因子：
2.8
通讯作者：
Takegawa, Kaoru
中科院分区：
文献类型：
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作者：
Matsunaga, Emiko;Tanaka, Yutaka;Takegawa, Kaoru
虽然β-D-呋喃半乳糖苷酶（Galf酶）水解β-D-呋喃半乳糖（Galf）的寡糖已在各种生物体的特点，迄今为止没有Galf特异性Galf酶编码基因已在曲霉真菌报道。根据已鉴定的细菌半乳糖醛酸酶的氨基酸序列，我们在构巢曲霉基因组中发现了两个半乳糖醛酸特异性半乳糖醛酸酶候选基因AN 2395（gfgA）和AN 3200（gfgB）。事实上，重组GfgA和GfgB蛋白表现出Galf特异性Galf-酶活性，但没有可检测的α-L-阿拉伯呋喃糖苷酶（Araf-酶）活性。系统发育分析表明，曲霉属有两种类型：一种是含有一个GfgA和GfgB的直向同源物，另一种是只含有一个直向同源物，其中烟曲霉（Aspergillus fumigatus）有一个直向同源物Galf-ase Afu 2g 14520。与GfgA和GfgB不同，重组Afu 2g 14520蛋白显示出比Galf-ase更高的Araf-ase活性。底物特异性的测定显示，虽然GfgA和GfgB都是外切型Galf-酶并水解β-（1，5）和β-（1，6）键，但与GfgB相比，GfgA更有效地水解β-（1，6）-连接的Galf-寡糖。总的来说，我们的研究结果表明，半乳糖醛酸酶在曲霉属物种可能有一个合作降解半乳糖醛酸含寡糖取决于环境条件的作用。(C)2020年，生物技术学会，日本。All rights reserved.
Although beta-D-galactofuranosidases (Galf-ases) that hydrolyze beta-D-galactofuranose (Galf)-containing oligosaccharides have been characterized in various organisms, to date no Galf-specific Galf-ase-encoding genes have been reported in Aspergillus fungi. Based on the amino acid sequences of previously identified bacterial Galf-ases, here we found two candidate Galf-specific Galf-ase genes AN2395 (gfgA) and AN3200 (gfgB) in the genome of Aspergillus nidulans. Indeed, recombinant GfgA and GfgB proteins exhibited Galf-specific Galf-ase activity, but no detectable alpha-L-arabinofuranosidase (Araf-ase) activity. Phylogenetic analysis of GfgA and GfgB orthologs indicated that there are two types of Aspergillus species: those containing one ortholog each for GfgA and GfgB; and those containing only one ortholog in total, among which Aspergillus fumigatus there is a representative with a single ortholog Galf-ase Afu2g14520. Unlike GfgA and GfgB, the recombinant Afu2g14520 protein showed higher Araf-ase activity than Galf-ase activity. An assay of substrate specificity revealed that although GfgA and GfgB are both exo-type Galf-ases and hydrolyze beta-(1,5) and beta-(1,6) linkages, GfgA hydrolyzes beta-(1,6)-linked Galf-oligosaccharide more effectively as compared with GfgB. Collectively, our findings indicate that Galf-ases in Aspergillus species may have a role in cooperatively degrading Galf-containing oligosaccharides depending on environmental conditions. (C) 2020, The Society for Biotechnology, Japan. All rights reserved.