Role of zinc in catalytic activity of carbonic anhydrase IX.
Role of zinc in catalytic activity of carbonic anhydrase IX.
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锌在碳酸酐酶 IX 催化活性中的作用。
DOI：
10.1016/j.abb.2012.03.017
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发表时间：
2012
影响因子：
3.9
通讯作者：
Frost,SusanC
中科院分区：
文献类型：
--
作者：
Tu,Chingkuang;Foster,Lauren;Alvarado,Andrea;McKenna,Robert;Silverman,DavidN;Frost,SusanC
碳酸酐酶（carbonic anhydrases，CA）是一类锌依赖性金属酶。以前的研究已经报道，重组形式的碳酸酐酶IX（CAIX），一种在实体瘤中表达的CA的膜结合形式，似乎被低水平的锌激活，独立于其在催化位点的充分研究的作用。在这项研究中，我们试图确定CAIX是否在其天然环境中受到锌的刺激。MDA-MB-231乳腺癌细胞响应于缺氧表达CAIX。我们比较了CAIX活性与膜鬼分离缺氧细胞与完整的缺氧细胞。采用膜进样质谱法直接测定CA活性。在膜血影中，低浓度的锌对CAIX活性的影响很小，尽管高浓度的锌是抑制性的。在完整细胞中，锌对CAIX活性没有显著影响。这表明，与纯化形式相比，当CAIX处于其天然膜环境中时，对锌的敏感性明显降低。
The carbonic anhydrases (CAs) in the α class are zinc-dependent metalloenzymes. Previous studies have reported that recombinant forms of carbonic anhydrase IX (CAIX), a membrane-bound form of CA expressed in solid tumors, appear to be activated by low levels of zinc independent of its well-studied role at the catalytic site. In this study, we sought to determine if CAIX is stimulated by zinc in its native environment. MDA-MB-231 breast cancer cells express CAIX in response to hypoxia. We compared CAIX activity associated with membrane ghosts isolated from hypoxic cells with that in intact hypoxic cells. We measured CA activity directly using18O exchange from13CO2into water determined by membrane inlet mass spectrometry. In membrane ghosts, there was little effect of zinc at low concentrations on CAIX activity, although at high concentration zinc was inhibitory. In intact cells, zinc had no significant effect on CAIX activity. This suggests that there is an appreciable decrease in sensitivity to zinc when CAIX is in its natural membrane milieu compared to the purified forms.