Bu Yifan, Zhang Tao, Jiang Bo, Chen Jingjing
State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
International Joint Laboratory on Food Safety, Jiangnan University, Wuxi 214122, China.
Foods. 2021 Apr 11;10(4):831. doi: 10.3390/foods10040831.
D-allulose is an epimer of D-fructose at the C-3 position. With similar sweetness to sucrose and a low-calorie profile, D-allulose has been considered a promising functional sweetener. D-psicose 3-epimerase (DPEase; EC 5.1.3.30) catalyses the synthesis of D-allulose from D-fructose. Immobilised enzymes are becoming increasingly popular because of their better stability and reusability. However, immobilised DPEase generally exhibits less activity or poses difficulty in separation. This study aimed to obtain immobilised DPEase with high catalytic activity, stability, and ease of separation from the reaction solution. In this study, DPEase was immobilised on an amino-epoxide support, ReliZyme HFA403/M (HFA), in four steps (ion exchange, covalent binding, glutaraldehyde crosslinking, and blocking). Glycine-blocked (four-step immobilisation) and unblocked (three-step immobilisation) immobilised DPEase exhibited activities of 103.5 and 138.8 U/g support, respectively, but contained equal amounts of protein. After incubation at 60 °C for 2 h, the residual activity of free enzyme decreased to 12.5%, but the activities of unblocked and blocked DPEase remained at 40.9% and 52.3%, respectively. Immobilisation also altered the substrate specificity of the enzyme, catalysing L-sorbose to L-tagatose and D-tagatose to D-sorbose. Overall, the immobilised DPEase with intense multipoint attachment, especially glycine-blocked DPEase, showed better properties than the free form, providing a superior potential for D-allulose biosynthesis.
D-阿洛酮糖是D-果糖在C-3位的差向异构体。由于D-阿洛酮糖与蔗糖甜度相似且热量低,它被认为是一种有前景的功能性甜味剂。D-阿洛酮糖3-差向异构酶(DPEase;EC 5.1.3.30)催化由D-果糖合成D-阿洛酮糖。固定化酶因其更好的稳定性和可重复使用性而越来越受欢迎。然而,固定化DPEase通常活性较低或在分离方面存在困难。本研究旨在获得具有高催化活性、稳定性且易于从反应溶液中分离的固定化DPEase。在本研究中,DPEase通过四个步骤(离子交换、共价结合、戊二醛交联和封闭)固定在氨基环氧载体ReliZyme HFA403/M(HFA)上。甘氨酸封闭的(四步固定化)和未封闭(三步固定化)固定化DPEase的活性分别为103.5和138.8 U/g载体,但蛋白质含量相等。在60℃孵育2小时后,游离酶的残余活性降至12.5%,但未封闭和封闭的DPEase活性分别保持在40.9%和52.3%。固定化还改变了酶的底物特异性,催化L-山梨糖生成L-塔格糖以及D-塔格糖生成D-山梨糖。总体而言,具有强多点附着的固定化DPEase,尤其是甘氨酸封闭的DPEase,表现出比游离形式更好的性能,为D-阿洛酮糖生物合成提供了更好的潜力。