Evidence for compartmentalized adenylate kinase catalysis serving a high energy phosphoryl transfer function in rat skeletal muscle.
Evidence for compartmentalized adenylate kinase catalysis serving a high energy phosphoryl transfer function in rat skeletal muscle.
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DOI：
10.1016/s0021-9258(19)40230-5
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发表时间：
1990-01
期刊：
影响因子：
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通讯作者：
R. Zeleznikar;R. Heyman;R. Graeff;T. Walseth;S. Dawis;E. A. Butz;N. D. Goldberg
中科院分区：
文献类型：
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作者：
R. Zeleznikar;R. Heyman;R. Graeff;T. Walseth;S. Dawis;E. A. Butz;N. D. Goldberg
在完整的肌肉中腺苷酸激酶活性的动力学和亚细胞区室化的第一个表征已经完成了使用大鼠隔膜平衡与[18 O]水。腺苷酸激酶催化的磷酰基转移速率通过ADP和ATP中18 O标记的β-磷酰基的出现来测量，所述18 O标记的β-磷酰基是由新合成的18 O标记的γ-ATP转移到AMP产生的。腺苷酸激酶催化的独特特征在完整细胞中未被发现，这是从无细胞分析中不可预测的。这种酶的活性，在非收缩肌肉中被限制到1/1000的估计Vmax（无细胞），显然是因为有限的ADP的可用性，是本地化的亚细胞区室，增加的大小和/或数量与收缩频率。收缩也导致腺苷酸激酶速度的频率依赖性增加（4 Hz时为22倍），缺氧也是如此（35倍）。当ATP、ADP和AMP的水平维持在非常接近其基础稳态时，腺苷酸激酶活性的这些增强速率（相当于在大约1分钟内处理所有细胞ATP和ADP）发生。完整细胞中腺苷酸激酶催化动力学的这些特征表明，从ADP快速产生AMP的速率被同样快速的AMP磷酸化速率平衡，没有任何腺嘌呤核苷酸的净合成或积累。核苷酸磷酸化的这种快速加工符合所提出的方案，其中腺苷酸激酶系统提供了将糖酵解代谢产生的高能磷酸化作为β-ADP转移到肌肉中利用ATP的组分的独特功能。
The first characterization of the kinetics and subcellular compartmentation of adenylate kinase activity in intact muscle has been accomplished using rat diaphragm equilibrated with [18O]water. Rates of adenylate kinase-catalyzed phosphoryl transfer were measured by appearance of 18O-labeled beta-phosphoryls in ADP and ATP resulting from the transfer to AMP of newly synthesized 18O-labeled gamma-ATP. Unique features of adenylate kinase catalysis were uncovered in the intact cell not predictable from cell free analysis. This enzyme activity, which in non-contracting muscle is limited to 1/1000 of the estimated Vmax (cell free) apparently because of restricted ADP availability, is localized in subcellular compartments that increase in size and/or number with contractile frequency. Contraction also causes frequency-dependent increments in adenylate kinase velocity (22-fold at 4 Hz) as does oxygen deprivation (35-fold). These enhanced rates of adenylate kinase activity, equivalent to processing all the cellular ATP and ADP in approximately 1 min, occur when levels of ATP, ADP, and AMP are maintained very near their basal steady state. These characteristics of the dynamics of adenylate kinase catalysis in the intact cell demonstrate that rapid rates of AMP production from ADP are balanced by equally rapid rates of AMP phosphorylation with no net synthesis or accumulation of any adenine nucleotide. This rapid processing of nucleotide phosphoryls conforms to a proposed scheme whereby the adenylate kinase system provides the unique function of transferring, as beta-ADP, high energy phosphoryls generated by glycolytic metabolism to ATP-utilizing components in muscle.