Determination of xanthine oxidoreductase activity in broilers: Effect of pH and temperature of the assay and distribution in tissues
Determination of xanthine oxidoreductase activity in broilers: Effect of pH and temperature of the assay and distribution in tissues
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DOI：
10.3382/ps.2009-00278
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发表时间：
2009-11-01
期刊：
影响因子：
4.4
通讯作者：
Klandorf, H.
中科院分区：
文献类型：
--
作者：
Carro, M. D.;Falkenstein, E.;Klandorf, H.
黄嘌呤氧化还原酶（XOR）是负责合成尿酸的酶，尿酸主要以脱氢酶形式存在于鸟类中。尿酸是鸟类含氮化合物代谢的主要最终产物，它作为抗氧化剂可以减少氧化应激。尽管这种酶很重要，但 XOR 在生理正常鸡中的组织分布尚不清楚。在这项研究中，我们分析了 7 周和 10 周龄肉鸡的 8 种组织提取物的 XOR 活性。在任何组织中均未发现因年龄而导致的 XOR 活性差异。肝脏和肾脏表现出最大的活性，肾脏的活性约为肝脏活性的89%。肠和胰腺中的酶活性分别约为肝脏的60%和37%。所有胸肌、心脏和肺样本均显示出酶活性，但其值仅为肝脏中酶活性的 3.0%、1.2% 和 0.6%。在十分之三的大脑样本中也检测到了酶活性的痕迹，但在血浆中没有发现酶活性。我们的结果表明，鸡中的 XOR 分布与哺乳动物中的不同，其中在肝脏和肠道中发现最高水平。另一个目标是评估 pH（7.2、7.7、8.2 和 8.7）和温度（25 和 41 C）对肝脏和肾脏样品中酶活性的影响。温度对两种组织的影响相似，25 摄氏度时的酶活性约为 41 摄氏度时的 30%。在 41 摄氏度时，随着 pH 值从 8.7 降至 7.2，肝脏和肾脏中的酶活性呈二次方下降。尽管肝脏中的酶活性在 pH 8.7 或 8.2 时没有差异，但在 pH 8.2 时测得肾脏中的最高活性。我们的结果表明，酶在鸡肝和肾中的最适pH值在8.2左右。
Xanthine oxidoreductase (XOR) is the enzyme responsible for the synthesis of uric acid, which exists primarily in the dehydrogenase form in birds. Uric acid is the major end product of the metabolism of nitrogen-containing compounds in birds and it functions as an antioxidant to reduce oxidative stress. Despite the importance of this enzyme, the tissue distribution of XOR in physiologically normal chickens is not well known. In this study, we analyzed XOR activity in extracts of 8 tissues from broilers at 7 and 10 wk of age. No differences in XOR activity due to the age were found in any tissue. Liver and kidney showed the greatest activity, that in the kidney being about 89% of the activity in the liver. Enzyme activity in intestine and pancreas was about 60 and 37% of that in the liver. All breast muscle, heart, and lung samples showed enzyme activity, but values were only 3.0, 1.2, and 0.6% of those found in the liver. Traces of enzyme activity were also detected in 3 out of 10 brain samples, and no activity was found in the plasma. Our results show that XOR distribution in chickens differs from that in mammals, in which the highest levels have been found in liver and intestine. An additional objective was the evaluation of the effect of pH (7.2, 7.7, 8.2, and 8.7) and temperature (25 and 41 C) on the enzyme activity in liver and kidney samples. Temperature had a similar effect on both tissues, with the activity at 25 degrees C being about 30% of that measured at 41 degrees C. At 41 degrees C, the enzyme activity in liver and kidney decreased quadratically as pH decreased from 8.7 to 7.2. The highest activity in kidney was measured at pH 8.2, although there were no differences between enzyme activities at pH 8.7 or 8.2 in the liver. Our results indicate that the optimum pH of the enzyme in chicken liver and kidney is around 8.2.