Regulation of AMP deaminase by phosphoinositides
Regulation of AMP deaminase by phosphoinositides
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DOI：
10.1074/jbc.274.36.25701
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发表时间：
1999-09-03
影响因子：
4.8
通讯作者：
Theibert, AB
中科院分区：
文献类型：
--
作者：
Sims, B;Mahnke-Zizelman, KM;Theibert, AB
AMP脱氨酶(AMPD)将AMP转化为IMP，是腺苷分解代谢途径的关键组成部分，是一种种类繁多且高度调控的酶。在这份报告中，我们发现AMPD和磷脂酰肌醇之间的高亲和力相互作用是调节该酶的机制。我们证明，内源性大鼠脑AMPD和人AMPD3重组酶特异性地结合基于肌醇的亲和探针和含有磷脂酰肌醇4，5-二磷酸的混合脂质胶束。此外，我们发现磷脂酰肌醇特异性地抑制AMPD的催化活性，4，5-二磷酸磷脂酰肌醇是最有效的抑制剂，对野生型人AMPD3重组酶具有纯的非竞争性抑制作用，K-I为110 nM。新霉素是一种磷脂酰肌醇结合药物，可以通过体外处理从膜组分中释放AMPD活性。此外，在体内调节肌醇磷脂水平会导致可溶的和膜相关的AMPD活性池发生变化。预测的人AMPD3序列含有Plecktrin同源结构域和(R/K)X-n(R/K)XKK序列，这两个序列都是磷脂酰肌醇结合基序。AMPD和肌醇磷脂之间的相互作用可能介导酶的膜定位，并调节体内的催化活性。
AMP deaminase (AMPD) converts AMP to IMP and is a diverse and highly regulated enzyme that is a key component of the adenylate catabolic pathway. In this report, we identify the high affinity interaction between AMPD and phosphoinositides as a mechanism for regulation of this enzyme. We demonstrate that endogenous rat brain AMPD and the human AMPD3 recombinant enzymes specifically bind inositide-based affinity probes and to mixed lipid micelles that contain phosphatidylinositol 4,5-bisphosphate. Moreover, we show that phosphoinositides specifically inhibit AMPD catalytic activity, Phosphatidylinositol 4,5-bisphosphate is the most potent inhibitor, effecting pure noncompetitive inhibition of the wild type human AMPD3 recombinant enzyme with a K-i of 110 nM. AMPD activity can be released from membrane fractions by in vitro treatment with neomycin, a phosphoinositide-binding drug. In addition, in vivo modulation of phosphoinositide levels leads to a change in the soluble and membrane-associated pools of AMPD activity. The predicted human AMPD3 sequence contains plecktrin homology domains and (R/ K)X-n(R/K)XKK sequences, both of which are characterized phosphoinositide-binding motifs. The interaction between AMPD and phosphoinositides may mediate membrane localization of the enzyme and function to modulate catalytic activity in vivo.