Zeleznikar R J, Dzeja P P, Goldberg N D
Department of Biochemistry, University of Minnesota, Medical School, Minneapolis 55455, USA.
J Biol Chem. 1995 Mar 31;270(13):7311-9. doi: 10.1074/jbc.270.13.7311.
We previously suggested that an importance of adenylate kinase (AdK) in skeletal muscle is to function as a high energy phosphoryl transfer system regulating ATP generation in correspondence with its consumption by specific cellular processes. The present experiments are intended to define the ATP-generating system coupled to and regulated by AdK-catalyzed phosphotransfer in skeletal muscle and also to examine the relationship between AdK- and creatine kinase (CK)-catalyzed phosphotransfer. Rates of phosphoryl transfer catalyzed by AdK were assessed in intact, isolated rat diaphragm by determining rates of AMP phosphorylation with endogenously generated [gamma-18O]ATP under conditions of altered anaerobic and aerobic ATP production. AdK-catalyzed phosphoryl transfer rates accelerated incrementally up to 12-fold in direct proportion to stimulated contractile frequency in parallel with equivalent increases in rates of ATP generation by lactate producing glycolysis. Stoichiometric equivalent increases of AdK-catalyzed phosphotransfer and anaerobic ATP production also occurred up to more than 20-fold when oxidative phosphorylation was impaired by either O2 deprivation or treatment with KCN or p-(trifluoromethoxy)-phenylhydrazone. These enhanced rates of AMP phosphorylation were balanced by virtually identically increased rates of AdK-catalyzed generation of AMP. This AMP was traced to arise from AdK-catalyzed phosphotransfer involving ADP generated by a muscle ATPase. Increased AdK-catalyzed phosphotransfer paired with the apparent compensatory increase in ATP generation by anaerobic glycolysis in oxygen-deprived muscle occurred coincident with diminished rates of CK-catalyzed phosphoryl transfer indicative of a pairing between oxidatively produced ATP and CK-catalyzed phosphotransfer. A metabolic model consistent with these results and conforming to the Mitchell general principle of vectorial ligand conduction is suggested.
我们之前曾提出，腺苷酸激酶（AdK）在骨骼肌中的一个重要作用是作为一种高能磷酸转移系统，根据特定细胞过程对ATP的消耗来调节ATP的生成。本实验旨在确定与骨骼肌中AdK催化的磷酸转移相偶联并受其调节的ATP生成系统，并研究AdK与肌酸激酶（CK）催化的磷酸转移之间的关系。在完整的、分离的大鼠膈肌中，通过在厌氧和需氧ATP生成改变的条件下，用内源性生成的[γ-18O]ATP测定AMP磷酸化速率，评估AdK催化的磷酸转移速率。AdK催化的磷酸转移速率与乳酸生成糖酵解产生ATP的速率同等增加，与刺激的收缩频率成正比，最高可加速12倍。当氧化磷酸化因缺氧或用KCN或对-（三氟甲氧基）-苯腙处理而受损时，AdK催化的磷酸转移和厌氧ATP生成的化学计量当量增加也会发生，最高可达20倍以上。这些增强的AMP磷酸化速率实际上与AdK催化的AMP生成速率同等增加相平衡。这种AMP被追踪到源于AdK催化的磷酸转移，涉及由肌肉ATP酶产生的ADP。在缺氧肌肉中，AdK催化的磷酸转移增加与厌氧糖酵解产生ATP的明显代偿性增加同时出现，这与CK催化的磷酸转移速率降低相一致，表明氧化产生的ATP与CK催化的磷酸转移之间存在配对关系。本文提出了一个与这些结果一致并符合米切尔矢量配体传导一般原则的代谢模型。
