Martens-Uzunova Elena S, Zandleven Joris S, Benen Jaques A E, Awad Hanem, Kools Harrie J, Beldman Gerrit, Voragen Alphons G J, Van den Berg Johan A, Schaap Peter J
Section Fungal Genomics, Laboratory of Microbiology, Wageningen University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands.
Biochem J. 2006 Nov 15;400(1):43-52. doi: 10.1042/BJ20060703.
The fungus Aspergillus niger is an industrial producer of pectin-degrading enzymes. The recent solving of the genomic sequence of A. niger allowed an inventory of the entire genome of the fungus for potential carbohydrate-degrading enzymes. By applying bioinformatics tools, 12 new genes, putatively encoding family 28 glycoside hydrolases, were identified. Seven of the newly discovered genes form a new gene group, which we show to encode exoacting pectinolytic glycoside hydrolases. This group includes four exo-polygalacturonan hydrolases (PGAX, PGXA, PGXB and PGXC) and three putative exo-rhamnogalacturonan hydrolases (RGXA, RGXB and RGXC). Biochemical identification using polygalacturonic acid and xylogalacturonan as substrates demonstrated that indeed PGXB and PGXC act as exo-polygalacturonases, whereas PGXA acts as an exo-xylogalacturonan hydrolase. The expression levels of all 21 genes were assessed by microarray analysis. The results from the present study demonstrate that exo-acting glycoside hydrolases play a prominent role in pectin degradation.
黑曲霉是一种工业生产果胶降解酶的真菌。最近黑曲霉基因组序列的解析使得对该真菌整个基因组中潜在的碳水化合物降解酶进行了清查。通过应用生物信息学工具，鉴定出了12个假定编码28家族糖苷水解酶的新基因。新发现的7个基因形成了一个新的基因簇，我们证明其编码外切作用的果胶olytic糖苷水解酶。该基因簇包括4种外切聚半乳糖醛酸酶（PGAX、PGXA、PGXB和PGXC）和3种假定的外切鼠李糖半乳糖醛酸酶（RGXA、RGXB和RGXC）。以聚半乳糖醛酸和木糖半乳糖醛酸为底物的生化鉴定表明，PGXB和PGXC确实作为外切聚半乳糖醛酸酶起作用，而PGXA作为外切木糖半乳糖醛酸酶起作用。通过微阵列分析评估了所有21个基因的表达水平。本研究结果表明，外切作用的糖苷水解酶在果胶降解中起重要作用。
