Although β-d-galactofuranosidases (Galf-ases) that hydrolyze β-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 α-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 β-(1,5) and β-(1,6) linkages, GfgA hydrolyzes β-(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.

虽然β- d -galactofuranosidases（加˚F -ases）水解β- d -galactofuranose（加˚F）含寡糖已经表征在多种生物没有加日期˚F特异性半乳糖˚F -ase编码基因已经报道在曲霉菌中。根据先前鉴定的细菌Gal f -ase的氨基酸序列，我们在构巢曲霉的基因组中发现了两个候选的Gal f-特异性Gal f -ase基因AN2395（gfgA）和AN3200（gfgB）。实际上，重组GfgA和GfgB蛋白表现出Gal f-特异性Gal f-酶活性，但是没有可检测的α- 1- α-呋喃糖苷酶（Ara f -ase）活性。对GfgA和GfgB直系同源物的系统进化分析表明，曲霉属菌种有两种类型：GfgA和GfgB分别含有一个直系同源物的曲霉。以及仅包含一个直向同源物的那些，其中烟曲霉中有一个代表，带有一个直向同源物Gal f -ase Afu2g14520。与GfgA和GfgB不同，重组Afu2g14520蛋白显示的Ara f-酶活性高于Gal f酶活性。底物特异性的测定表明，尽管GfgA和GfgB都是外切型Gal f-酶并水解β-（1,5）和β-（1,6）键，但GfgA水解了β-（1,6）-键与GfgB相比，Gal f-寡糖更有效。总的来说，我们的发现表明，取决于环境条件，曲霉属物种中的Gal f-酶可能在协同降解含Gal f的寡糖中起作用。