Department of Biology, Faculty of Sciences, University of Guilan, Rasht, Iran.
Department of Biology, Faculty of Sciences, University of Guilan, Rasht, Iran.
Int J Biol Macromol. 2019 Jan;121:173-182. doi: 10.1016/j.ijbiomac.2018.10.006. Epub 2018 Oct 2.
Due to the need for calf rennet alternatives, many attempts have been made to find new proteases. A novel cysteine protease with milk-clotting activity was purified from Ficus johannis by cation exchange chromatography. The protease was stable in various pH (3.0-10.5) with the optimum at 6.5 and showed its maximum activity at 60 °C. The K and V values of the enzyme were obtained to be 0.604 mg/ml and 0.0273 μmol Tyr/min, respectively. The purified protease exhibited considerable activity towards κ-casein in comparison to α-casein and β-casein. The enzyme was almost completely active in the presence of high salt concentrations. Besides, it had high stability against autodigestion. The content of free amino acids was determined by HPLC, where leucine, lysine, valine, γ-aminobutyric acid and tyrosine were the most abundant amino acids. The cheese manufactured by using the purified protease showed similar textural properties and physico-chemical compositions to cheese produced using commercial rennet. Considering the special characteristics, including high milk-clotting activity, considerable stability over wide ranges of pH and temperature, resistance towards solvents, salts, and surfactants, the new protease might be the promising candidate for the dairy industry as well as other food and biotechnological industries.
由于需要替代小牛皱胃酶，人们进行了许多尝试以寻找新的蛋白酶。本研究通过阳离子交换层析从榕树叶中纯化得到了一种具有凝乳活性的新型半胱氨酸蛋白酶。该蛋白酶在 pH 3.0-10.5 的范围内稳定，最适 pH 为 6.5，并在 60°C 时表现出最大活性。酶的 K 和 V 值分别为 0.604 mg/ml 和 0.0273 μmol Tyr/min。与 α-酪蛋白和 β-酪蛋白相比，该纯化蛋白酶对 κ-酪蛋白表现出相当大的活性。该酶在高盐浓度下几乎完全具有活性。此外，它对自消化具有很高的稳定性。通过 HPLC 测定游离氨基酸含量，亮氨酸、赖氨酸、缬氨酸、γ-氨基丁酸和酪氨酸是最丰富的氨基酸。使用纯化蛋白酶生产的奶酪在质地特性和物理化学组成方面与使用商业凝乳酶生产的奶酪相似。考虑到其特殊特性，包括高凝乳活性、在较宽的 pH 和温度范围内的相当稳定性、对溶剂、盐和表面活性剂的抗性，该新型蛋白酶可能是乳品行业以及其他食品和生物技术行业的有前途的候选者。
