The serpin SQN-5 is a dual mechanistic-class inhibitor of serine and cysteine proteinases
The serpin SQN-5 is a dual mechanistic-class inhibitor of serine and cysteine proteinases
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DOI：
10.1021/bi015999x
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发表时间：
2002-03-05
期刊：
影响因子：
2.9
通讯作者：
Silverman, GA
中科院分区：
文献类型：
--
作者：
Al-Khunaizi, M;Luke, CJ;Silverman, GA
SQN-5是一种小鼠丝氨酸蛋白酶抑制剂，与人丝氨酸蛋白酶抑制剂SCCA 1（SERPINB 3）和SCCA 2（SERPINB 4）高度相似。以前的研究表明，SQN-5的生化活性表明，这种丝氨酸蛋白酶抑制剂，像SCCA 2，抑制糜蛋白酶样酶肥大细胞糜蛋白酶和组织蛋白酶G。使用木瓜蛋白酶样半胱氨酸蛋白酶的扩展面板，我们现在表明，SQN-5，像SCCA 1，抑制组织蛋白酶K，L，S和V，但不抑制组织蛋白酶B或H。这些相互作用的特征是抑制的化学计量比接近1：1，二级速率常数> 10（4）M-（1）s（-1）。反应位点环（RSL）切割分析表明，SQN-5采用不同的反应中心，以中和丝氨酸和半胱氨酸蛋白酶。据我们所知，这是第一个丝氨酸蛋白酶抑制剂，作为一个双重抑制剂胰凝乳蛋白酶样丝氨酸和木瓜蛋白酶样半胱氨酸蛋白酶通过采用RSL依赖性抑制机制。丝氨酸蛋白酶抑制剂抑制丝氨酸和/或木瓜蛋白酶样半胱氨酸蛋白酶的能力可能不是哺乳动物进化中最近发生的事件。系统发育研究表明，SCCA和SQN基因是从大约2.5亿至2.8亿年前的共同祖先进化而来的。当事实上，哺乳动物和鸟类分歧约3 - 10亿年前被认为是一个祖先的SCCA/SQN-样丝氨酸蛋白酶抑制剂具有双重抑制活性可能存在于许多哺乳动物的基因组。
SQN-5 is a mouse serpin that is highly similar to the human serpins SCCA1 (SERPINB3) and SCCA2 (SERPINB4). Previous studies characterizing the biochemical activity of SQN-5 showed that this serpin, like SCCA2, inhibited the chymotrypsin-like enzymes mast cell chymase and cathepsin G. Using an expanded panel of papain-like cysteine proteinases, we now show that SQN-5, like SCCA1, inhibited cathepsins K, L, S, and V but not cathepsin B or H. These interactions were characterized by stoichiometries of inhibition that were nearly 1:1 and second-order rate constants of > 10(4) M-(1) s(-1). Reactive site loop (RSL) cleavage analysis showed that SQN-5 employed different reactive centers to neutralize the serine and cysteine proteinases. To our knowledge, this is the first serpin that serves as a dual inhibitor of both chymotrypsin-like serine and the papain-like cysteine proteinases by employing an RSL-dependent inhibitory mechanism. The ability of serpins to inhibit both serine and/or papain-like cysteine proteinases may not be a recent event in mammalian evolution. Phylogenetic studies suggested that the SCCA and SQN genes evolved from a common ancestor approximately 250-280 million years ago. When the fact that mammals and birds diverged approximately 3 10 million years ago is considered, an ancestral SCCA/ SQN-like serpin with dual inhibitory activity may be present in many mammalian genomes.