Glycolysis Is Governed by Growth Regime and Simple Enzyme Regulation in Adherent MDCK Cells

Due to its vital importance in the supply of cellular pathways with energy and precursors, glycolysis has been studied for several decades regarding its capacity and regulation. For a systems-level understanding of the Madin-Darby canine kidney (MDCK) cell metabolism, we couple a segregated cell growth model published earlier with a structured model of glycolysis, which is based on relatively simple kinetics for enzymatic reactions of glycolysis, to explain the pathway dynamics under various cultivation conditions. The structured model takes into account in vitro enzyme activities, and links glycolysis with pentose phosphate pathway and glycogenesis. Using a single parameterization, metabolite pool dynamics during cell cultivation, glucose limitation and glucose pulse experiments can be consistently reproduced by considering the cultivation history of the cells. Growth phase-dependent glucose uptake together with cell-specific volume changes generate high intracellular metabolite pools and flux rates to satisfy the cellular demand during growth. Under glucose limitation, the coordinated control of glycolytic enzymes re-adjusts the glycolytic flux to prevent the depletion of glycolytic intermediates. Finally, the model's predictive power supports the design of more efficient bioprocesses.鉴于糖酵解（glycolysis）为细胞通路提供能量与前体物质的核心作用，数十年来学界围绕其代谢能力与调控机制开展了大量研究。为实现对Madin-Darby犬肾（MDCK）细胞代谢的系统级解析，本研究将此前发表的分区细胞生长模型，与基于糖酵解酶促反应相对简化动力学的结构化糖酵解模型相结合，以阐释不同培养条件下的通路动态变化。该结构化模型纳入了体外酶活数据，并将糖酵解与磷酸戊糖途径（pentose phosphate pathway）、糖原生成（glycogenesis）相连接。通过单一参数化方案，结合细胞的培养历史，本模型可一致性复现细胞培养、葡萄糖限制及葡萄糖脉冲实验中的代谢物池动态变化。依赖于生长阶段的葡萄糖摄取，结合细胞特异性体积变化，可产生高水平的细胞内代谢物池与通量速率，以满足细胞生长过程中的代谢需求。在葡萄糖限制条件下，糖酵解酶的协同调控可重新调整糖酵解通量，避免糖酵解中间产物被耗竭。最终，该模型的预测能力可为更高效生物工艺的设计提供支撑。