Zhang Nannan, Yin Shiyan, Zhang Wei, Gong Xiaojian, Zhang Na, Fang Kai, Ge Honghua
Institute of Health Sciences, School of Life Sciences, Anhui University , Hefei, Anhui 230601, China.
J Agric Food Chem. 2017 Aug 30;65(34):7569-7578. doi: 10.1021/acs.jafc.7b02849. Epub 2017 Aug 17.
Aminopeptidases are a group of exopeptidases that catalyze the removal of a wide range of N-terminal amino acid residues from peptides and proteins. They have many important commercial applications in the food industry. We determined the crystal structure of an aminopeptidase LapB from Legionella pneumophila. The overall structure reveals that the N-terminal protease-associated (PA) domain presents a new fold and shields the active site cavity of the conserved C-terminal peptidase domain. The steady-state kinetic analysis of LapB and the PA domain deletion mutant indicate that the PA domain inhibited enzyme activity of the peptidase domain. Interestingly, the activity of LapB was largely increased by various organic solvents such as ethanol, propanol, and methanol at the concentration of 60% (v/v). CD analysis provided evidence that organic solvents induce the PA domain conformational changes that eliminate the inhibition role. The unique properties indicate the application potential of LapB in the food processing industry.
氨肽酶是一类外肽酶，可催化从肽和蛋白质中去除多种N端氨基酸残基。它们在食品工业中有许多重要的商业应用。我们测定了嗜肺军团菌氨肽酶LapB的晶体结构。整体结构表明，N端蛋白酶相关（PA）结构域呈现出一种新的折叠方式，并屏蔽了保守的C端肽酶结构域的活性位点腔。LapB和PA结构域缺失突变体的稳态动力学分析表明，PA结构域抑制了肽酶结构域的酶活性。有趣的是，在60%（v/v）浓度的乙醇、丙醇和甲醇等各种有机溶剂作用下，LapB的活性大幅增加。圆二色性分析提供了证据，表明有机溶剂诱导PA结构域构象变化，从而消除了抑制作用。这些独特的性质表明LapB在食品加工业中的应用潜力。
