Department of Biotechnology and Enzyme Science, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstr. 25, 70599, Stuttgart, Germany.
Appl Microbiol Biotechnol. 2020 Jan;104(1):187-199. doi: 10.1007/s00253-019-10225-2. Epub 2019 Nov 26.
Deamidation is a promising tool to improve solubility and other functional properties of food proteins. One possibility of protein deamidation is the use of a protein glutaminase (PG; EC 3.5.1.44), an enzyme that catalyzes the deamidation of internal glutamine residues in proteins to glutamic acid residues. The PG from Chryseobacterium proteolyticum is the only one described in literature to date and is commercially available (Amano Enzyme Inc., Japan; PGA). Based on a similarity search, we discovered a predicted, uncharacterized protein from Bacteroides helcogenes and this protein was verified as a PG. After recombinant production and purification, the novel PG (BH-PG) was biochemically characterized and compared with PGA. Some advantageous characteristics for potential application of BH-PG compared with PGA were the higher temperature stability (residual activity after 24 h of incubation at 50 °C was 87% for BH-PG and 2% for PGA), an optimum pH value at acidic conditions (pH 5.5) and less product inhibition by ammonia that is released during the deamidation of proteins (residual activity after adding 40 mM ammonia was 77% for BH-PG and 27% for PGA). Finally, the applicability of BH-PG and PGA was compared by gluten deamidation experiments. Consequently, the final solubility of the nearly insoluble food protein gluten was 94% after BH-PG treatment, whereas the solubility was around 66% when using PGA.
脱酰胺作用是一种提高食品蛋白质溶解性和其他功能特性的有前途的方法。蛋白质脱酰胺的一种可能性是使用蛋白谷氨酰胺酶（PG；EC 3.5.1.44），该酶催化蛋白质内部谷氨酰胺残基向谷氨酸残基的脱酰胺作用。到目前为止，文献中仅描述了来自黄色杆菌（Chryseobacterium proteolyticum）的 PG，并且可商购（Amano Enzyme Inc.，日本；PGA）。基于相似性搜索，我们从拟杆菌属（Bacteroides helcogenes）中发现了一种预测的、未表征的蛋白，并且证实该蛋白为 PG。经过重组生产和纯化后，对新型 PG（BH-PG）进行了生化特性分析，并与 PGA 进行了比较。与 PGA 相比，BH-PG 具有一些潜在应用的优势特性，包括更高的热稳定性（在 50°C 孵育 24 小时后，残余活性分别为 BH-PG 的 87%和 PGA 的 2%）、在酸性条件下的最佳 pH 值（pH 5.5）和较少的由蛋白质脱酰胺作用释放的氨产物抑制（添加 40 mM 氨后，残余活性分别为 BH-PG 的 77%和 PGA 的 27%）。最后，通过谷朊粉脱酰胺实验比较了 BH-PG 和 PGA 的适用性。结果，在 BH-PG 处理后，几乎不溶性食品蛋白质谷朊粉的最终溶解度达到 94%，而使用 PGA 时的溶解度约为 66%。
