Bioengineering a synthetic enzyme for the production of authentic human milk oligosaccharides.

生物工程合成酶用于生产真正的母乳低聚糖。

• 批准号: BB/R008744/1
• 负责人: Kimberly Watson
• 金额: $ 53.14万
• 依托单位: University of Reading
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FR008744%2F1
• 关键词: Bioengineering; synthetic; enzyme; production; authentic

It is generally accepted that milk is good for us. It contains nutrients, such as protein, carbohydrates, fat, minerals and vitamins that are known to promote healthy bones, teeth, skin and help build muscle and can help in the prevention of some diseases, such as osteoporosis, cardiovascular disease and even cancer.Until the turn of the century, a wet nurse was the only safe alternative to breastfeeding. This is because breast milk composition is different from cow's milk; the composition of proteins is different and the structural diversity of the carbohydrates is distinctly different. But not all women are able to breastfeed, due to emotional and/or physical conditions such as postpartum surgery, exhaustion or poor nutrition. And yet, breast milk remains the gold standard for infant nutrition and manufacturers aim to make infant formulas as close to human milk as possible. One group of carbohydrates in cow's milk called galactooligosaccharides (GOS) is the primary additive in infant milk formulae to help bridge some of the difference. GOS consist of short chains of sugar molecules (called galactose), and are synthesised from another milk sugar (lactose) by enzymes called lactase or beta-galactosidase. These soluble, non-digestible carbohydrates are added as a prebiotic in an attempt to stimulate growth of 'healthy bacteria' in the gut and replicate the beneficial properties of human breast milk. In infant nutrition, GOS have been shown to decrease the risks of atopic dermatitis and may be involved in allergy and infection prevention and to increase the absorption of important minerals such as calcium, iron, magnesium and zinc. However, prebiotic GOS composition is similar, but not identical, to the sugars found in human milk oligosaccharides (HMOs); galactose sugars do not naturally occur in breast milk. In contrast, fucosylated sugars, namely 2'-fucosyllactose, are richly found in the milk of Secretor women (who secrete their blood type antigens into body fluids and tissues, contributing to immunity). The use of GOS and fructooligosaccharides (short chains of fructose-based sugar molecules) in infant formulas, neither of which mimic HMOs.Relevant to this proposal, some beta-galactosidases can utilise fucose sugars to yield fucosylated-oligosaccharides (FucOS; short chains of fucose-based sugar molecules); an important component of breast milk. However, the mechanism by which beta-galactosidases are able to produce FucOS and how this function might be related to their structure are unknown. Our recent work, toward optimisation of GOS products, using a beta-galactosidase enzyme (known as BbgIII), has provided significant insight into specific modifications that directly affect enzyme function and subsequent product formation. We developed novel BbgIII enzymes that give rise to desirable GOS products for improved production of the prebiotic supplement Bimuno (a type of GOS). During the course of this work, we also discovered that by making specific modifications, two variants of the enzyme were able to synthesise 20 different FucOS products that could more closely mimic HMOs.The overall aim of this project is to optimise our BbgIII enzyme variants to provide specific and desirable FucOS; arguably more authentic HMOs, that exhibit a beneficial effect on the gut microbiome for use in infant formulae and medical nutrition. Our approach is unique, as current methods to produce HMOs are costly and lack structural diversity in the carbohydrates produced, which provides strong industry and societal drivers to develop more cost effective and structurally diverse authentic HMOs.

人们普遍认为牛奶对我们有益。它含有蛋白质、碳水化合物、脂肪、矿物质和维生素等营养物质，已知可促进骨骼、牙齿、皮肤健康，帮助增强肌肉，并有助于预防一些疾病，如骨质疏松症、心血管疾病甚至癌症。直到世纪之交，乳母是母乳喂养的唯一安全替代方案。这是因为母乳的成分与牛奶不同；蛋白质的组成不同，碳水化合物的结构多样性也明显不同。但由于产后手术、疲惫或营养不良等情绪和/或身体状况，并非所有女性都能母乳喂养。然而，母乳仍然是婴儿营养的黄金标准，制造商的目标是使婴儿配方奶粉尽可能接近母乳。牛奶中的一组碳水化合物称为低聚半乳糖 (GOS)，它是婴儿配方奶粉中的主要添加剂，有助于弥补一些差异。 GOS 由短链糖分子（称为半乳糖）组成，由另一种乳糖（乳糖）通过乳糖酶或 β-半乳糖苷酶合成。这些可溶性、不易消化的碳水化合物作为益生元添加，试图刺激肠道中“健康细菌”的生长，并复制母乳的有益特性。在婴儿营养方面，GOS 已被证明可以降低特应性皮炎的风险，并可能参与过敏和感染的预防，并增加钙、铁、镁和锌等重要矿物质的吸收。然而，益生元 GOS 的成分与母乳低聚糖 (HMO) 中的糖相似，但不完全相同；半乳糖不会天然存在于母乳中。相比之下，分泌者女性（将血型抗原分泌到体液和组织中，有助于增强免疫力）的乳汁中富含岩藻糖基化糖，即 2'-岩藻糖基乳糖。在婴儿配方奶粉中使用 GOS 和低聚果糖（基于果糖的短链糖分子），两者均不模仿 HMO。与该提案相关的是，一些 β-半乳糖苷酶可以利用岩藻糖产生岩藻糖基化低聚糖（FucOS；短链低聚果糖）。基于岩藻糖的糖分子）；母乳的重要组成部分。然而，β-半乳糖苷酶产生 FucOS 的机制以及该功能如何与其结构相关尚不清楚。我们最近的工作是使用 β-半乳糖苷酶（称为 BbgIII）优化 GOS 产品，为直接影响酶功能和后续产品形成的特定修饰提供了重要的见解。我们开发了新型 BbgIII 酶，可产生理想的 GOS 产品，以改善益生元补充剂 Bimuno（一种 GOS）的生产。在这项工作的过程中，我们还发现，通过进行特定的修饰，该酶的两种变体能够合成 20 种不同的 FucOS 产品，这些产品可以更接近地模仿 HMO。该项目的总体目标是优化我们的 BbgIII 酶变体提供具体且理想的FucOS；可以说是更真实的 HMO，对肠道微生物组表现出有益的影响，可用于婴儿配方奶粉和医疗营养品。我们的方法是独特的，因为目前生产 HMO 的方法成本高昂，并且所生产的碳水化合物缺乏结构多样性，这为开发更具成本效益和结构多样化的正宗 HMO 提供了强大的行业和社会驱动力。