Enzymatic characteristics of two adenylate kinases, AdkA and AdkB, from Myxococcus xanthus
Enzymatic characteristics of two adenylate kinases, AdkA and AdkB, from Myxococcus xanthus
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来自黄色粘球菌的两种腺苷酸激酶 AdkA 和 AdkB 的酶学特征
DOI：
10.1093/jb/mvy112
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Kamatani Shiori
中科院分区：
文献类型：
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作者：
Kimura Yoshio;Yamamoto Hiroyuki;Kamatani Shiori
腺苷酸激酶 (Adk) 在能量代谢和细菌适应环境压力方面发挥着关键作用。我们之前已经证明，黄色粘球菌表达多磷酸激酶 1 (Ppk1)，在没有多磷酸盐的情况下也具有 Adk 活性。在这项研究中，我们研究了另外两个M的Adk活性。黄酶、AdkA 和 AdkB。二硫苏糖醇 (DTT) 提高了 AdkA 的活性，同时也增强了酶的稳定性。对 AdkA LID 结构域中存在的三个半胱氨酸残基（C130、C150 和 C153）进行定点诱变表明，C150S 和 C153S 突变体的 Adk 活性和稳定性不受 DTT 添加的影响，表明 AdkA 中 C150 和 C153 之间形成了二硫键。 AMP 的 AdkA 的 Km 分别比 ADP 和 ATP 的低 8 倍和 17 倍。 AdkB 是一种多磷酸激酶 2 (Ppk2) 同源物，缺乏 Ppk2 中间区域，因此缺乏 Ppk 活性。根据我们的分析，AdkB也具有Adk活性，并且其对底物的亲和力高于AdkA。因此，M. xanthus表达三种具有Adk活性的酶AdkA、AdkB和Ppk1，这可能在不同环境条件下支持细菌的能量代谢。
Adenylate kinase (Adk) plays a critical role in energy metabolism and adaptation of bacteria to environmental stresses. We have previously shown thatMyxococcus xanthusexpresses polyphosphate kinase 1 (Ppk1) that also has Adk activity in the absence of polyphosphates. In this study, we investigated the Adk activity of the other twoM. xanthusenzymes, AdkA and AdkB. The activity of AdkA was increased by dithiothreitol (DTT), which also enhanced enzyme stability. Site-directed mutagenesis of three cysteine residues (C130, C150, and C153) present in the LID domain of AdkA revealed that the Adk activity and stability of C150S and C153S mutants were not affected by DTT addition, suggesting formation of a disulfide bond between C150 and C153 in AdkA. TheKmof AdkA for AMP was 8 and 17 times lower than that for ADP and ATP, respectively. AdkB is a polyphosphate kinase 2 (Ppk2) homolog lacking the Ppk2 middle region and, consequently, Ppk activity. According to our analysis, AdkB also had Adk activity and its affinity for substrates was higher than that of AdkA. Thus,M. xanthusexpresses three enzymes, AdkA, AdkB, and Ppk1, with Adk activity, which may function to support energy metabolism of the bacteria in different environmental conditions.