Flipphi M J, Visser J, van der Veen P, de Graaff L H
Section Molecular Genetics of Industrial Microorganisms, Wageningen Agricultural University, The Netherlands.
Microbiology (Reading). 1994 Oct;140 ( Pt 10):2673-82. doi: 10.1099/00221287-140-10-2673.
Aspergillus niger secretes three glycosylated glycosyl hydrolases which are involved in degradation of the plant cell wall polysaccharide L-arabinan: alpha-L-arabinofuranosidases (ABF) A and B, and endo-1,5-alpha-L-arabinase (ABN) A. The nucleotide sequence of the previously cloned gene encoding ABF A (abfA) from A. niger was determined. The coding region contains seven introns. Mature ABF A comprises 603 amino acids with a molecular mass of 65.4 kDa as deduced from the nucleotide sequence. The secreted enzyme is N-glycosylated. The primary structures of the three A. niger arabinases characterized lack similarity. Regulation of arabinase expression upon induction by sugar beet pulp and by L-arabitol was studied as a function of time. This was done in wild-type A. niger as well as in transformants carrying multiple copies of either one of the ABF-encoding genes. Each arabinase gene responded differently upon a mycelial transfer to L-arabitol-containing medium. Extra copies of abfA or abfB led to a decreased expression level of ABN A, though the repression elicited by abfB is stronger and more persistent than that effected by abfA. Multiple copies of both abf genes influence expression of the other ABF similarly, but to a far less pronounced degree than they affect ABN A synthesis. Four putative promoter elements, shared by all three arabinase genes, could be involved in coordination of L-arabinan degradation by A. niger.
黑曲霉分泌三种糖基化的糖基水解酶，它们参与植物细胞壁多糖L-阿拉伯聚糖的降解：α-L-阿拉伯呋喃糖苷酶（ABF）A和B，以及内切-1,5-α-L-阿拉伯聚糖酶（ABN）A。测定了先前从黑曲霉克隆的编码ABF A（abfA）的基因的核苷酸序列。编码区包含7个内含子。根据核苷酸序列推导，成熟的ABF A由603个氨基酸组成，分子量为65.4 kDa。分泌的酶进行了N-糖基化修饰。已鉴定的三种黑曲霉阿拉伯聚糖酶的一级结构缺乏相似性。研究了在甜菜浆和L-阿拉伯糖醇诱导下，阿拉伯聚糖酶表达随时间的调控情况。在野生型黑曲霉以及携带任一ABF编码基因多拷贝的转化体中进行了此项研究。当菌丝体转移到含L-阿拉伯糖醇的培养基中时，每个阿拉伯聚糖酶基因的反应都不同。abfA或abfB的额外拷贝导致ABN A的表达水平降低，不过abfB引发的抑制作用比abfA更强且更持久。两个abf基因的多拷贝对另一种ABF的表达有类似影响，但程度远不如它们对ABN A合成的影响。所有三种阿拉伯聚糖酶基因共有的四个推定启动子元件可能参与黑曲霉对L-阿拉伯聚糖降解的协调过程。
