Prathumpai W, McIntyre M, Nielsen J
Centre for Process Biotechnology, BioCentrum-DTU, Building 223, Technical University of Denmark, 2800, Lyngby, Denmark.
Appl Microbiol Biotechnol. 2004 Feb;63(6):748-53. doi: 10.1007/s00253-003-1409-1. Epub 2003 Aug 15.
The catabolism of glucose and xylose was studied in a wild type and creA deleted (carbon catabolite de-repressed) strain of Aspergillus nidulans. Both strains were cultivated in bioreactors with either glucose or xylose as the sole carbon source, or in the presence of both sugars. In the cultivations on single carbon sources, it was demonstrated that xylose acted as a carbon catabolite repressor (xylose cultivations), while the enzymes in the xylose utilisation pathway were also subject to repression in the presence of glucose (glucose cultivations). In the wild type strain growing on the sugar mixture, glucose repression of xylose utilisation was observed; with xylose utilisation occurring only after glucose was depleted. This phenomenon was not seen in the creA deleted strain, where glucose and xylose were catabolised simultaneously. Measurement of key metabolites and the activities of key enzymes in the xylose utilisation pathway revealed that xylose metabolism was occurring in the creA deleted strain, even at high glucose concentrations. Conversely, in the wild type strain, activities of the key enzymes for xylose metabolism increased only when the effects of glucose repression had been relieved. Xylose was both a repressor and an inducer of xylanases at the same time. The creA mutation seemed to have pleiotropic effects on carbohydratases and carbon catabolism.
在米曲霉的野生型菌株和creA缺失（碳分解代谢去阻遏）菌株中研究了葡萄糖和木糖的分解代谢。两种菌株都在生物反应器中培养，以葡萄糖或木糖作为唯一碳源，或者在两种糖都存在的情况下培养。在单一碳源培养中，结果表明木糖起到碳分解代谢阻遏物的作用（木糖培养），而在葡萄糖存在时木糖利用途径中的酶也受到阻遏（葡萄糖培养）。在以糖混合物生长的野生型菌株中，观察到葡萄糖对木糖利用的阻遏作用；只有在葡萄糖耗尽后才会发生木糖利用。在creA缺失菌株中未观察到这种现象，该菌株中葡萄糖和木糖同时被分解代谢。对木糖利用途径中关键代谢物和关键酶活性的测量表明，即使在高葡萄糖浓度下，creA缺失菌株中也发生了木糖代谢。相反，在野生型菌株中，只有当葡萄糖阻遏作用解除时，木糖代谢关键酶的活性才会增加。木糖同时既是木聚糖酶的阻遏物又是诱导物。creA突变似乎对碳水化合物酶和碳分解代谢具有多效性作用。
