Evidence for the transport function of uricase, an oxidative enzyme.
Evidence for the transport function of uricase, an oxidative enzyme.
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尿酸酶（一种氧化酶）转运功能的证据。
DOI：
10.1152/ajprenal.1987.253.4.f702
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Abramson,RG
中科院分区：
文献类型：
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作者：
Pordy,WT;Lipkowitz,MS;Abramson,RG
在用磷脂酰胆碱和猪肝尿酸酶或白蛋白制备的蛋白脂质体和无蛋白脂质体中检查[2- 14 C]尿酸盐摄取。尿酸盐摄取仅在含有活性尿酸酶的脂蛋白体中明显。摄取是无法区分的存在和不存在的钠，钾，或氯化胆碱或向外定向羟基梯度的向内定向梯度。在尿酸盐摄取过程中，尿酸盐和尿囊素都在脂蛋白体内积累;然而，[2- 14 C]尿囊素不被脂蛋白体摄取。在反式、可饱和和竞争性抑制oxonate的未标记尿酸盐存在下，尿酸盐摄取加速，这一发现与载体介导的转运一致。最后，尿酸盐摄取和氧化的动力学几乎相同，这意味着转运蛋白是尿酸酶。因此，这些研究提供的证据表明，尿酸酶可以作为尿酸盐的转运蛋白插入脂质双层：通过尿酸酶转运既不依赖于阳离子（不是协同转运蛋白），也不依赖于可交换的阴离子（不是尿酸盐/阴离子交换剂）。此外，这些研究表明，尿酸盐和尿囊素都不会通过简单或非离子扩散穿过脂质双层。
[2-14C]urate uptake was examined in proteoliposomes prepared with phosphatidylcholine and either pig liver uricase or albumin, and in protein-free liposomes. Urate uptake was only evident in proteoliposomes that contained active uricase. Uptakes were indistinguishable in the presence and absence of inwardly directed gradients of sodium, potassium, or choline chloride or outwardly directed hydroxyl gradients. Both urate and allantoin accumulated within proteoliposomes during urate uptake; however, [2–14C]allantoin was not taken up by proteoliposomes. Urate uptake was accelerated in the presence of unlabeled urate in the trans position, saturable, and competitively inhibited by oxonate, findings consistent with carrier-mediated transport. Finally, the kinetics of urate uptake and oxidation were virtually identical, implying that the transporter is uricase. Thus, these studies provide evidence that uricase can function as a transport protein for urate when inserted in a lipid bilayer: transport via uricase is neither cation dependent (not a cotransporter) nor dependent on an exchangeable anion (not a urate/anion exchanger). Additionally, these studies demonstrate that neither urate nor allantoin cross lipid bilayers by simple or nonionic diffusion.