Vrabl Pamela, Mutschlechner Wolfgang, Burgstaller Wolfgang
University of Innsbruck, Institute of Microbiology, Technikerstrasse 25, 6020 Innsbruck, Austria.
Mycol Res. 2009 Dec;113(Pt 12):1422-32. doi: 10.1016/j.mycres.2009.09.011. Epub 2009 Oct 7.
Filamentous fungi are able to spill energy when exposed to energy excess by uncoupling catabolism from anabolism, e.g. via overflow metabolism. In current study we tested the hypothesis that overflow metabolism is regulated via the energetic status of the hyphae (i.e. energy charge, ATP concentration). This hypothesis was studied in Penicillium ochrochloron during the steady state of glucose- or ammonium-limited chemostat cultures as well as during three transient states ((i) glucose pulse to a glucose-limited chemostat, (ii) shift from glucose-limited to ammonium-limited conditions in a chemostat, and (iii) ammonium exhaustion in batch culture). Organic acids were excreted under all conditions, even during exponential growth in batch culture as well as under glucose-limited conditions in a chemostat. Partial uncoupling of catabolism and anabolism via overflow metabolism was thus constitutively present. Under all tested conditions, overflow metabolism was independent of the energy charge or the ATP concentration of the hyphae. There was a reciprocal correlation between glucose uptake rate and intracellular adenine nucleotide content. During all transients states a rapid decrease in energy charge and the concentrations of nucleotides was observed shortly after a change in glycolytic flux ("ATP paradoxon"). A possible connection between the change in adenine nucleotide concentrations and the purine salvage pathway is discussed.
丝状真菌在能量过剩时能够通过使分解代谢与合成代谢解偶联（例如通过溢流代谢）来释放能量。在当前研究中，我们测试了以下假设：溢流代谢是通过菌丝的能量状态（即能荷、ATP浓度）来调节的。在葡萄糖或铵限制的恒化器培养的稳态期间以及在三种瞬态状态（(i) 向葡萄糖限制的恒化器中添加葡萄糖脉冲，(ii) 在恒化器中从葡萄糖限制条件转变为铵限制条件，以及(iii) 分批培养中铵耗尽）下，对产黄青霉进行了该假设的研究。在所有条件下都会分泌有机酸，即使在分批培养的指数生长期以及恒化器中葡萄糖限制条件下也是如此。因此，通过溢流代谢实现的分解代谢与合成代谢的部分解偶联是持续存在的。在所有测试条件下，溢流代谢均与菌丝的能荷或ATP浓度无关。葡萄糖摄取速率与细胞内腺嘌呤核苷酸含量之间存在相互关系。在所有瞬态状态期间，在糖酵解通量变化后不久（“ATP悖论”），观察到能荷和核苷酸浓度迅速下降。讨论了腺嘌呤核苷酸浓度变化与嘌呤补救途径之间的可能联系。
