Ivanov Dmitri, Emonet Celine, Foata Francis, Affolter Michael, Delley Michelle, Fisseha Makda, Blum-Sperisen Stephanie, Kochhar Sunil, Arigoni Fabrizio
Nestlé Research Center, Vers-chez-les-Blanc, P. O. Box 44, CH-1000 Lausanne 26, Switzerland.
Nestlé Research Center, Vers-chez-les-Blanc, P. O. Box 44, CH-1000 Lausanne 26, Switzerland.
J Biol Chem. 2006 Jun 23;281(25):17246-17252. doi: 10.1074/jbc.M601678200. Epub 2006 Apr 20.
Serpins form a large class of protease inhibitors involved in regulation of a wide spectrum of physiological processes. Recently identified prokaryotic members of this protein family may provide a key to the evolutionary origins of the unique serpin fold and the associated inhibitory mechanism. We performed a biochemical characterization of a serpin from Bifidobacterium longum, an anaerobic Gram-positive bacterium that naturally colonizes human gastrointestinal tract. The B. longum serpin was shown to efficiently inhibit eukaryotic elastase-like proteases with a stoichiometry of inhibition close to 1. Porcine pancreatic elastase and human neutrophil elastase were inhibited with the second order association constants of 4.7 x 10(4) m(-1) s(-1) and 2.1 x 10(4) m(-1) s(-1), respectively. The B. longum serpin is expected to be active in the gastrointestinal tract, because incubation of the purified recombinant serpin with mouse feces produces a stable covalent serpin-protease adduct readily detectable by SDS-PAGE. Bifidobacteria may encounter both pancreatic elastase and neutrophil elastase in their natural habitat and protection against exogenous proteolysis may play an important role in the interaction between these commensal bacteria and their host.
丝氨酸蛋白酶抑制剂（Serpins）构成了一大类蛋白酶抑制剂，参与多种生理过程的调节。该蛋白家族中最近发现的原核成员可能为独特的丝氨酸蛋白酶抑制剂折叠结构及相关抑制机制的进化起源提供关键线索。我们对来自长双歧杆菌的一种丝氨酸蛋白酶抑制剂进行了生化特性分析，长双歧杆菌是一种厌氧革兰氏阳性菌，自然定殖于人类胃肠道。结果表明，长双歧杆菌丝氨酸蛋白酶抑制剂能有效抑制真核弹性蛋白酶样蛋白酶，抑制化学计量比接近1。猪胰弹性蛋白酶和人中性粒细胞弹性蛋白酶的二级结合常数分别为4.7×10⁴ m⁻¹ s⁻¹和2.1×10⁴ m⁻¹ s⁻¹。长双歧杆菌丝氨酸蛋白酶抑制剂预计在胃肠道中具有活性，因为将纯化的重组丝氨酸蛋白酶抑制剂与小鼠粪便一起孵育会产生一种稳定的共价丝氨酸蛋白酶抑制剂 - 蛋白酶加合物，通过SDS - PAGE很容易检测到。双歧杆菌在其天然生境中可能会遇到胰弹性蛋白酶和中性粒细胞弹性蛋白酶，抵御外源蛋白水解作用可能在这些共生细菌与其宿主之间的相互作用中发挥重要作用。
