Aboka Fredrick O, Heijnen Joseph J, van Winden Wouter A
Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
FEMS Yeast Res. 2009 Mar;9(2):191-201. doi: 10.1111/j.1567-1364.2008.00465.x.
In this research, two dynamic (13)C-labeling experiments confirmed turnover and rapid mobilization of stored glycogen and trehalose in an aerobic glucose-limited chemostat (D=0.05 h(-1)) culture of Saccharomyces cerevisiae. In one experiment, the continuous feed to an aerobic glucose-limited chemostat culture of S. cerevisiae was instantaneously switched from naturally labeled to fully (13)C labeled while maintaining the same feed rate before and after the switch. The dynamic replacements of naturally labeled intracellular glycolytic intermediates and CO(2) (in the off-gas) with their (13)C-labeled equivalents were measured. The data of this experiment suggest that the continuous turnover of glycogen and trehalose is substantial (c. 1/3 of the glycolytic flux). The second experiment combined the medium switch with a shiftup in the glucose feeding rate (dilution rate shiftup from 0.05 to 0.10 h(-1)). This experiment triggered a strong but transient mobilization of storage carbon, that was channelled into glycolysis, causing a significant disruption in the dynamic labeling profile of glycolytic intermediates. The off-gas measurements in the shiftup experiment confirmed a considerable transient influx of (12)C-carbon into glycolysis after the combined medium switch and dilution rate shiftup. This study shows that for accurate in vivo kinetic interpretation of rapid pulse experiments, glycogen and trehalose metabolism must be taken into account.
在本研究中，两项动态（13）C标记实验证实了酿酒酵母在有氧葡萄糖限制恒化器（D = 0.05 h(-1)）培养中储存的糖原和海藻糖的周转及快速动员。在一项实验中，将酿酒酵母有氧葡萄糖限制恒化器培养的连续进料瞬间从天然标记切换为完全（13）C标记，同时保持切换前后相同的进料速率。测量了天然标记的细胞内糖酵解中间体和CO(2)（废气中）被其（13）C标记等效物的动态替代情况。该实验数据表明糖原和海藻糖的持续周转量很大（约为糖酵解通量的1/3）。第二项实验将培养基切换与葡萄糖进料速率的阶跃增加（稀释率从0.05 h(-1)升至0.10 h(-1)）相结合。该实验引发了储存碳的强烈但短暂的动员，其被导入糖酵解，导致糖酵解中间体的动态标记谱发生显著破坏。阶跃增加实验中的废气测量证实，在培养基切换和稀释率阶跃增加相结合后，有相当数量的（12）C碳短暂流入糖酵解。本研究表明，为了对快速脉冲实验进行准确的体内动力学解释，必须考虑糖原和海藻糖的代谢。
