Department of Human Genetics, David Geffen School of Medicine at UCLA, 695 Charles E. Young Drive South, Los Angeles, CA 90095-7088, USA.
Department of Human Genetics, David Geffen School of Medicine at UCLA, 695 Charles E. Young Drive South, Los Angeles, CA 90095-7088, USA; Department of Chemical and Biomolecular Engineering, Henry Samueli School of Engineering and Applied Science at UCLA, 420 Westwood Plaza, Los Angeles, CA 90095, USA; Department of Chemical and Biomolecular Engineering, 1208D Building 90, Chemical and Nuclear Engineering Bldg, University of Maryland, College Park, MD 20742-2111, USA.
Mol Genet Metab. 2018 Aug;124(4):254-265. doi: 10.1016/j.ymgme.2018.06.001. Epub 2018 Jun 12.
Glycerol kinase (GK) is a multifunctional enzyme located at the interface of carbohydrate and fat metabolism. It contributes to both central carbon metabolism and adipogenesis; specifically, through its role as the ATP-stimulated translocation promoter (ASTP). GK overexpression leads to increased ASTP activity and increased fat storage in H4IIE cells. We performed metabolic flux analysis in human GK-overexpressing H4IIE cells and found that overexpressing cells had significantly altered fluxes through central carbon and lipid metabolism including increased flux through the pentose phosphate pathway and increased production of lipids. We also observed an equal contribution of glycerol to carbohydrate metabolism in all cell lines, suggesting that GK's alternate functions rather than its enzymatic function are important for these processes. To further elucidate the contributions of the enzymatic (phosphorylation) and alternative (ASTP) functions of GK in adipogenesis, we performed experiments on mammalian GK and E. coli GK. We determined that the ASTP function of GK (which is absent in E. coli GK) plays a greater role than the enzymatic activity in these processes. These studies further emphasize GK's diverse functionality and provides fundamental insights into the multiple protein functions of glycerol kinase.
甘油激酶 (GK) 是一种位于碳水化合物和脂肪代谢交界处的多功能酶。它既有助于中央碳代谢，也有助于脂肪生成；具体来说，通过其作为 ATP 刺激的易位启动子 (ASTP) 的作用。GK 过表达导致 ASTP 活性增加，H4IIE 细胞中的脂肪储存增加。我们在人 GK 过表达的 H4IIE 细胞中进行了代谢通量分析，发现过表达细胞的中央碳和脂质代谢通量发生了明显改变，包括戊糖磷酸途径通量增加和脂质产量增加。我们还观察到甘油在所有细胞系中对碳水化合物代谢的贡献相等，这表明 GK 的替代功能而不是其酶功能对这些过程很重要。为了进一步阐明 GK 在脂肪生成中的酶（磷酸化）和替代（ASTP）功能的贡献，我们在哺乳动物 GK 和大肠杆菌 GK 上进行了实验。我们确定 GK 的 ASTP 功能（大肠杆菌 GK 中不存在）在这些过程中比酶活性发挥更大的作用。这些研究进一步强调了 GK 的多功能性，并为甘油激酶的多种蛋白质功能提供了基本的见解。
