Molecular and physiological role of the trehalose-hydrolyzing α-glucosidase from Thermus thermophilus HB27
Molecular and physiological role of the trehalose-hydrolyzing α-glucosidase from Thermus thermophilus HB27
复制标题
DOI：
10.1128/jb.01794-07
复制
发表时间：
2008-04-01
影响因子：
3.2
通讯作者：
Empadinhas, Nuno
中科院分区：
文献类型：
--
作者：
Alarico, Susana;da Costa, Milton S.;Empadinhas, Nuno
海藻糖支持嗜热栖热菌菌株HB 27的生长，但基因组中缺乏明显的水解这种二糖的基因，导致我们寻找用于此目的的酶。我们表达了一个假定的α-葡萄糖苷酶基因（TTC 0107），其特征在于重组酶，并发现，优选的底物是α，α-1，1-海藻糖，α-葡萄糖苷酶之间的新功能。该酶还可以水解二糖曲二糖和蔗糖（α-1，2键）、黑曲霉糖和松二糖（α-1，3键）、明串珠菌二糖（α-1，5键）、异麦芽糖和帕拉金糖（α-1，6键）以及麦芽糖（α-1，4键）。然而，海藻糖不是T.嗜热菌株GK 24。来自菌株HB 27（LGEHNLPP）和GK 24（EPTAYHTL）的α-葡糖苷酶中含有8个氨基酸的肽的相互替换降低了前者水解海藻糖的能力，并为后者提供了海藻糖水解活性，表明LGEHNLPP是海藻糖识别所必需的。此外，α-葡萄糖苷酶基因的破坏显著影响了T.在补充有海藻糖、异麦芽糖、蔗糖或帕拉金糖的基本培养基中，在较低程度上用麦芽糖但不用纤维二糖（不是α-葡糖苷酶的底物），嗜热菌HB 27中的α-葡糖苷酶对这四种二糖的同化作用是重要的，但它也涉及麦芽糖催化。
Trehalose supports the growth of Thermus thermophilus strain HB27, but the absence of obvious genes for the hydrolysis of this disaccharide in the genome led us to search for enzymes for such a purpose. We expressed a putative alpha-glucosidase gene (TTC0107), characterized the recombinant enzyme, and found that the preferred substrate was alpha,alpha-1,1-trehalose, a new feature among alpha-glucosidases. The enzyme could also hydrolyze the disaccharides kojibiose and sucrose (alpha-1,2 linkage), nigerose and turanose (alpha-1,3), leucrose (alpha-1,5), isomaltose and palatinose (alpha-1,6), and maltose (alpha-1,4) to a lesser extent. Trehalose was not, however, a substrate for the highly homologous alpha-glucosidase from T. thermophilus strain GK24. The reciprocal replacement of a peptide containing eight amino acids in the alpha-glucosidases from strains HB27 (LGEHNLPP) and GK24 (EPTAYHTL) reduced the ability of the former to hydrolyze trehalose and provided trehalose-hydrolytic activity to the latter, showing that LGEHNLPP is necessary for trehalose recognition. Furthermore, disruption of the a-glucosidase gene significantly affected the growth of T. thermophilus HB27 in minimal medium supplemented with trehalose, isomaltose, sucrose, or palatinose, to a lesser extent with maltose, but not with cellobiose (not a substrate for the alpha-glucosidase), indicating that the alpha-glucosidase is important for the assimilation of those four disaccharides but that it is also implicated in maltose catabolism.