Binding of xanthine oxidase to glycosaminoglycans limits inhibition by oxypurinol
Binding of xanthine oxidase to glycosaminoglycans limits inhibition by oxypurinol
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DOI：
10.1074/jbc.m402077200
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发表时间：
2004-09-03
影响因子：
4.8
通讯作者：
Tarpey, MM
中科院分区：
文献类型：
--
作者：
Kelley, EE;Trostschansky, A;Tarpey, MM
虽然黄嘌呤氧化酶（XO）与糖胺聚糖（GAG）的结合导致其催化特性发生显著变化，但XO/GAG固定化对与临床相关抑制剂相互作用的影响尚不清楚。因此，使用饱和浓度的黄嘌呤确定了XO的抑制动力学。当XO与原型GAG肝素-琼脂糖6 B（HS 6 B-XO）结合时，黄嘌呤形成尿酸的灭活速率低于溶液中XO的灭活速率（k（inact）= 0.24 vs 0.39 min（-1））。此外，羟嘌呤醇对HS 6 B-XO的总体抑制常数（Ki）是游离XO的2-5倍（451对85 nM）。单价电子通量（O-2（自由基阴离子）的形成）减少了结合的XO肝素从28.5%的游离XO的18.7%的GAG固定的XO。与HS 6 B- XO获得的结果相似，XO与牛主动脉内皮细胞的结合使该酶对羟嘌呤醇的抑制具有抵抗力，达到了类似于50%的抑制。这些结果表明，在HS 6 B和细胞模型中XO的GAG固定基本上限制了XO的羟嘌呤醇抑制，这一事件与XO及其产物可能发挥致病作用的临床情况下使用XO的吡唑抑制剂具有重要相关性。
Although the binding of xanthine oxidase (XO) to glycosaminoglycans (GAGs) results in significant alterations in its catalytic properties, the consequence of XO/GAG immobilization on interactions with clinically relevant inhibitors is unknown. Thus, the inhibition kinetics of oxypurinol for XO was determined using saturating concentrations of xanthine. When XO was bound to a prototypical GAG, heparin-Sepharose 6B (HS6B-XO), the rate of inactivation for uric acid formation from xanthine was less than that for XO in solution (k(inact) = 0.24 versus 0.39 min(-1)). Additionally, the overall inhibition constant (K-i) of oxypurinol for HS6B-XO was 2-5-fold greater than for free XO ( 451 versus 85 nM). Univalent electron flux (O-2(radical anion) formation) was diminished by the binding of XO to heparin from 28.5% for free XO to 18.7% for GAG-immobilized XO. Similar to the results obtained with HS6B- XO, the binding of XO to bovine aortic endothelial cells rendered the enzyme resistant to inhibition by oxypurinol, achieving similar to 50% inhibition. These results reveal that GAG immobilization of XO in both HS6B and cell models substantially limits oxypurinol inhibition of XO, an event that has important relevance for the use of pyrazolo inhibitors of XO in clinical situations where XO and its products may play a pathogenic role.