Gao Xianli, Yin Yiyun, Zhou Cunshan
School of Food and Biological Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, China.
Food Chem. 2018 Feb 1;240:377-385. doi: 10.1016/j.foodchem.2017.07.081. Epub 2017 Jul 18.
A salt-tolerant aspartyl aminopeptidase (approximately 57kDa) from Aspergillus oryzae 3.042 was purified and identified. Specific inhibitor experiments indicated that it was an aminopeptidase containing Zn. Its optimal and stable pH values and temperatures were 7 and 50°C, respectively. Its relative activity remained beyond 30% in 3M NaCl solution for 15d, and its K and V were slightly affected in 3M NaCl solution, indicating its excellent salt-tolerance. A comprehensive analysis including protein homology modelling, molecular dynamics simulation, secondary structure, acidic residues and hydrophobicity of interior residues demonstrated that aspartyl aminopeptidase had a greater stability than non-salt-tolerant protease in high salinity. Higher contents of ordered secondary structures, more salt bridges between hydrated surface acidic residues and specific basic residues and stronger hydrophobicity of interior residues were the salt-tolerance mechanisms of aspartyl aminopeptidase.
对米曲霉3.042中一种耐盐天冬氨酰氨基肽酶（约57kDa）进行了纯化和鉴定。特异性抑制剂实验表明它是一种含锌的氨基肽酶。其最适pH值和稳定pH值以及温度分别为7和50°C。在3M NaCl溶液中15天其相对活性仍超过30%，且其Km和Vmax在3M NaCl溶液中略有影响，表明其具有优异的耐盐性。包括蛋白质同源性建模、分子动力学模拟、二级结构、内部残基的酸性残基和疏水性在内的综合分析表明，在高盐度下，天冬氨酰氨基肽酶比不耐盐的蛋白酶具有更高的稳定性。有序二级结构含量更高、水合表面酸性残基与特定碱性残基之间更多的盐桥以及内部残基更强的疏水性是天冬氨酰氨基肽酶的耐盐机制。
