Kleczkowski Leszek A, Igamberdiev Abir U
Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, 901 87, Umeå, Sweden.
Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B3X9, Canada.
J Plant Physiol. 2023 Jan;280:153901. doi: 10.1016/j.jplph.2022.153901. Epub 2022 Dec 12.
Free magnesium (Mg) represents a powerful signal arising from interconversions of adenylates (ATP, ADP and AMP). This is a consequence of the involvement of adenylate kinase (AK) which equilibrates adenylates and uses defined species of Mg-complexed and Mg-free adenylates in both directions of its reaction. However, cells contain also other reversible Mg-dependent enzymes that equilibrate non-adenylate nucleotides (uridylates, cytidylates and guanylates), i.e. nucleoside monophosphate kinases (NMPKs) and nucleoside diphosphate kinase (NDPK). Here, we propose that AK activity is tightly coupled to activities of NMPK and NDPK, linking adenylate equilibrium to equilibria of other nucleotides, and with [Mg] controlling the ratios of Mg-chelated and Mg-free nucleotides. This coupling establishes main hubs for adenylate-driven equilibration of non-adenylate nucleotides, with [Mg] acting as signal arising from all nucleotides rather than adenylates only. Further consequences involve an overall adenylate control of UTP-, GTP- and CTP-dependent pathways and the availability of substrates for RNA and DNA synthesis.
游离镁（Mg）代表了由腺苷酸（ATP、ADP和AMP）相互转化产生的一种强大信号。这是腺苷酸激酶（AK）参与的结果，该酶使腺苷酸达到平衡，并在其反应的两个方向上使用特定种类的镁络合腺苷酸和无镁腺苷酸。然而，细胞中还含有其他可逆的镁依赖性酶，它们能使非腺苷酸核苷酸（尿苷酸、胞苷酸和鸟苷酸）达到平衡，即核苷单磷酸激酶（NMPK）和核苷二磷酸激酶（NDPK）。在此，我们提出AK活性与NMPK和NDPK的活性紧密偶联，将腺苷酸平衡与其他核苷酸的平衡联系起来，并且[Mg]控制着镁螯合核苷酸和无镁核苷酸的比例。这种偶联建立了由腺苷酸驱动的非腺苷酸核苷酸平衡的主要枢纽，其中[Mg]作为来自所有核苷酸而非仅腺苷酸的信号。进一步的结果包括对UTP、GTP和CTP依赖性途径的整体腺苷酸控制以及RNA和DNA合成底物的可用性。
