Department of Biological Mechanisms and Functions, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Nagoya-shi, Aichi 464-8601, Japan.
Appl Microbiol Biotechnol. 2012 Jun;94(6):1629-35. doi: 10.1007/s00253-012-3874-x. Epub 2012 Jan 18.
AmyR, a fungal transcriptional activator responsible for induction of amylolytic genes in Aspergillus nidulans, localizes to the nucleus in response to the physiological inducer isomaltose. Maltose, kojibiose, and D: -glucose were also found to trigger the nuclear localization of GFP-AmyR. Isomaltose- and kojibiose-triggered nuclear localization was not inhibited by the glucosidase inhibitor, castanospermine, while maltose-triggered localization was inhibited. Thus, maltose itself does not appear to be an direct inducer, but its degraded or transglycosylated product does. Non-metabolizable D: -glucose analogues were also able to trigger the nuclear localization, implying that these sugars, except maltose, directly function as the inducers of AmyR nuclear entry. The inducing activity of D: -glucose was 4 orders-of-magnitude weaker compared with isomaltose. Although D: -glucose has the ability to induce α-amylase production, this activity would generally be masked by CreA-dependent carbon catabolite repression. Significant induction of α-amylase by D: -glucose was observed in creA-defective A. nidulans.
AmyR 是一种真菌转录激活因子，负责诱导 Aspergillus nidulans 中的淀粉分解基因的表达。AmyR 在响应生理诱导剂异麦芽糖时定位于细胞核。发现麦芽糖、昆布二糖和 D: -葡萄糖也能触发 GFP-AmyR 的核定位。异麦芽糖和昆布二糖触发的核定位不受葡萄糖苷酶抑制剂金雀花碱的抑制，而麦芽糖触发的定位则受到抑制。因此，麦芽糖本身似乎不是直接诱导物，而是其降解或转糖苷产物。非代谢性 D: -葡萄糖类似物也能够触发核定位，这意味着这些糖（除麦芽糖外）直接作为 AmyR 核进入的诱导剂发挥作用。与异麦芽糖相比，D: -葡萄糖的诱导活性弱 4 个数量级。尽管 D: -葡萄糖具有诱导α-淀粉酶产生的能力，但这种活性通常会被 CreA 依赖性碳分解代谢物阻遏所掩盖。在 creA 缺陷型 A. nidulans 中观察到 D: -葡萄糖对α-淀粉酶的显著诱导。
