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，牛奶对我们有好处。它含有诸如蛋白质，碳水化合物，脂肪，矿物质和维生素等营养素，这些营养素已知可以促进健康的骨骼，牙齿，皮肤，皮肤并有助于锻炼肌肉，并可以帮助预防某些疾病，例如骨质疏松，心血管疾病，甚至是本世纪的癌症。这是因为母乳成分与牛奶不同。蛋白质的组成不同，碳水化合物的结构多样性明显不同。但是，并非所有妇女都能够因情绪和/或身体状况（例如产后手术，疲惫或营养不良）而进行母乳喂养。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尽可能靠近人类牛奶。牛奶中的一组碳水化合物称为半乳糖醇（GOS）是婴儿牛奶配方中的主要添加剂，可帮助弥合一些差异。 GO由糖分子的短链（称为半乳糖）组成，并由称为乳糖酶或β-半乳糖苷酶的酶从另一种牛奶糖（乳糖）中合成。这些可溶的，不可消化的碳水化合物是作为益生元添加的，以刺激肠道中“健康细菌”的生长并复制人类母乳的有益特性。在婴儿营养中，GOS已被证明会降低特应性皮炎的风险，并可能参与预防过敏和感染，并增加重要矿物质的吸收，例如钙，铁，镁和锌。然而，益生元的GOS组成与人乳寡糖（HMOS）中发现的糖相似，但并不相同。半乳糖糖在母乳中不自然​​发生。相反，在分泌妇女的牛奶中发现了岩藻糖基化的糖，即2'5脉酸糖（2'-烟酸糖）（她们将其血型抗原分泌到体液和组织中，从而有助于免疫力）。在婴儿配方中使用GOS和GOS和果糖含糖（基于果糖的糖分子的短链），它们都不模仿HMOS.Relevant，因此，某些β-半乳糖苷酶可以利用β-半乳糖酶来产生岩藻糖糖来产生葡萄糖基化的糖糖（富甲酸糖）的葡萄糖基糖基糖基糖的短核糖浆;母乳的重要组成部分。但是，β-半乳糖苷酶能够产生FUCO的机制以及该功能可能与其结构相关的机制尚不清楚。我们最近使用β-半乳糖苷酶（称为BBGIII）优化GOS产品的工作为直接影响酶功能和随后产物形成的特定修饰提供了重要的见解。我们开发了新型的BBGIII酶，这些酶产生了理想的GOS产品，以改善益生元补充剂Bimuno（一种GOS）的产生。在这项工作过程中，我们还发现，通过进行特定的修改，两种酶的变体能够合成20种不同的FUCOS产品，可以更紧密地模拟HMOS。该项目的总体目的是优化我们的BBGIIII酶变体以提供特定和可取的烟粉；可以说，更真实的HMO，对肠道微生物组具有有益的作用，可用于婴儿配方和医疗营养。我们的方法是独一无二的，因为当前生产HMO的方法是昂贵的，并且缺乏生产的碳水化合物的结构多样性，这为强大的行业和社会驱动因素提供了更具成本效益和结构上多样性的真实HMO。