Glucose metabolism comprises numerous amphibolic metabolites that provide precursors for not only the synthesis of cellular building blocks but also for ATP production. In this study, we tested how phosphofructokinase-1 (PFK1) activity controls the fate of glucose-derived carbon in murine hearts in vivo. PFK1 activity was regulated by cardiac-specific overexpression of kinase- or phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase transgenes in mice (termed Glyco^Lo or Glyco^Hi mice, respectively). Dietary delivery of ¹³C₆-glucose to these mice, followed by deep network metabolic tracing, revealed that low rates of PFK1 activity promote selective routing of glucose-derived carbon to the purine synthesis pathway to form 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR). Consistent with a mechanism of physical channeling, we found multimeric protein complexes that contained phosphoribosylaminoimidazole carboxylase (PAICS)—an enzyme important for AICAR biosynthesis, as well as chaperone proteins such as Hsp90 and other metabolic enzymes. We also observed that PFK1 influenced glucose-derived carbon deposition in glycogen, but did not affect hexosamine biosynthetic pathway activity. These studies demonstrate the utility of deep network tracing to identify metabolic channeling and changes in biosynthetic pathway activity in the heart in vivo and present new potential mechanisms by which metabolic branchpoint reactions modulate biosynthetic pathways.

葡萄糖代谢包括许多两栖代谢物，它们不仅为细胞结构单元的合成提供前体，还为 ATP 的产生提供前体。在这项研究中，我们测试了磷酸果糖激酶 1 (PFK1) 活性如何在体内控制小鼠心脏中葡萄糖衍生碳的命运。^{PFK1 活性受小鼠（分别称为 Glyco Lo}或 Glyco ^Hi小鼠）中激酶或磷酸酶缺陷型 6-磷酸果糖-2-激酶/果糖-2,6-双磷酸酶转基因的心脏特异性过表达调节。膳食输送¹³ C ₆对这些小鼠进行葡萄糖，然后进行深度网络代谢追踪，结果表明，低速率的 PFK1 活性促进葡萄糖衍生的碳选择性路由至嘌呤合成途径，形成 5-氨基咪唑-4-甲酰胺核糖核苷酸 (AICAR)。与物理通道机制一致，我们发现多聚体蛋白复合物含有磷酸核糖氨基咪唑羧化酶 (PAICS)——一种对 AICAR 生物合成很重要的酶，以及伴侣蛋白，如 Hsp90 和其他代谢酶。我们还观察到 PFK1 影响糖原中葡萄糖衍生的碳沉积，但不影响己糖胺生物合成途径的活性。这些研究证明了深度网络追踪在识别体内心脏代谢通道和生物合成途径活性变化方面的实用性并提出代谢分支点反应调节生物合成途径的新潜在机制。