Song Peng, Cheng Lei, Tian Kangming, Zhang Meng, Mchunu Nokuthula Peace, Niu Dandan, Singh Suren, Prior Bernard, Wang Zheng-Xiang
College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457 China.
Department of Biological Chemical Engineering, College of Chemical Engineering and Materials Science, Tianjin University of Science and Technology, Tianjin, 300457 China.
3 Biotech. 2020 Jul;10(7):303. doi: 10.1007/s13205-020-02292-4. Epub 2020 Jun 13.
Two new aspartic proteases, PepAb and PepAc (encoded by and ), were heterologously expressed and biochemically characterized from F0215. They possessed a typical structure of pepsin-type aspartic protease with the conserved active residues D (84, 115), Y (131, 168) and D (281, 326), while their identity in amino acid sequences was only 19.0%. PepAb had maximum activity at pH 2.5 and 50 °C and PepAc at 3.0 and 50 °C. The specific activities of PepAb and PepAc toward casein were 1368.1 and 2081.4 U/mg, respectively. Their activities were significantly promoted by Cu and Mn and completely inhibited by pepstatin. PepAb exhibited higher catalytic efficiency ( / ) toward soy protein isolates than casein, while PepAc showed higher catalytic efficiency toward casein. The hydrolysis capacities of PepAb and PepAc on soy protein isolates were slightly lower than that of previously identified aspartic protease, PepA (aspergillopepsin I), while the resultant peptide profiles were remarkably different for all three proteases.
从F0215中异源表达并对两种新的天冬氨酸蛋白酶PepAb和PepAc（分别由 和 编码）进行了生化特性分析。它们具有胃蛋白酶型天冬氨酸蛋白酶的典型结构，带有保守的活性残基D（84, 115）、Y（131, 168）和D（281, 326），而它们氨基酸序列的同一性仅为19.0%。PepAb在pH 2.5和50°C时具有最大活性，PepAc在pH 3.0和50°C时具有最大活性。PepAb和PepAc对酪蛋白的比活性分别为1368.1和2081.4 U/mg。它们的活性受到铜和锰的显著促进，并被胃蛋白酶抑制剂完全抑制。PepAb对大豆分离蛋白的催化效率（/）高于酪蛋白，而PepAc对酪蛋白的催化效率更高。PepAb和PepAc对大豆分离蛋白的水解能力略低于先前鉴定的天冬氨酸蛋白酶PepA（曲霉胃蛋白酶I），而这三种蛋白酶产生的肽谱明显不同。
