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Database mining and transcriptional analysis of genes encoding inulin-modifying enzymes of Aspergillus niger
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| Zeitschriftentitel: | Microbiology |
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| Personen und Körperschaften: | , , , , , , |
| In: | Microbiology, 152, 2006, 10, S. 3061-3073 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
Microbiology Society
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| Schlagwörter: |
| Zusammenfassung: | <jats:p>As a soil fungus, <jats:italic>Aspergillus niger</jats:italic> can metabolize a wide variety of carbon sources, employing sets of enzymes able to degrade plant-derived polysaccharides. In this study the genome sequence of <jats:italic>A. niger</jats:italic> strain CBS 513.88 was surveyed, to analyse the gene/enzyme network involved in utilization of the plant storage polymer inulin, and of sucrose, the substrate for inulin synthesis in plants. In addition to three known activities, encoded by the genes <jats:italic>suc1</jats:italic> (invertase activity; designated <jats:italic>sucA</jats:italic>), <jats:italic>inuE</jats:italic> (exo-inulinase activity) and <jats:italic>inuA</jats:italic>/<jats:italic>inuB</jats:italic> (endo-inulinase activity), two new putative invertase-like proteins were identified. These two putative proteins lack N-terminal signal sequences and therefore are expected to be intracellular enzymes. One of these two genes, designated <jats:italic>sucB</jats:italic>, is expressed at a low level, and its expression is up-regulated when <jats:italic>A. niger</jats:italic> is grown on sucrose- or inulin-containing media. Transcriptional analysis of the genes encoding the sucrose- (<jats:italic>sucA</jats:italic>) and inulin-hydrolysing enzymes (<jats:italic>inuA</jats:italic> and <jats:italic>inuE</jats:italic>) indicated that they are similarly regulated and all strongly induced on sucrose and inulin. Analysis of a Δ<jats:italic>creA</jats:italic> mutant strain of <jats:italic>A. niger</jats:italic> revealed that expression of the extracellular inulinolytic enzymes is under control of the catabolite repressor CreA. Expression of the inulinolytic enzymes was not induced by fructose, not even in the Δ<jats:italic>creA</jats:italic> background, indicating that fructose did not act as an inducer. Evidence is provided that sucrose, or a sucrose-derived intermediate, but not fructose, acts as an inducer for the expression of inulinolytic genes in <jats:italic>A. niger</jats:italic>.</jats:p> |
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| Umfang: | 3061-3073 |
| ISSN: |
1350-0872
1465-2080 |
| DOI: | 10.1099/mic.0.29051-0 |