Awofiranye Adeola E, Baytas Sultan N, Xia Ke, Badri Abinaya, He Wenqin, Varki Ajit, Koffas Mattheos, Linhardt Robert J
Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.
Department of Chemical and Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, USA.
AMB Express. 2020 Aug 17;10(1):144. doi: 10.1186/s13568-020-01084-6.
N-glycolyl chondroitin (Gc-CN) is a metabolite of N-glycolylneuraminic acid (Neu5Gc), a sialic acid that is commonly found in mammals, but not humans. Humans can incorporate exogenous Neu5Gc into their tissues from eating red meat. Neu5Gc cannot be biosynthesized by humans due to an evolutionary mutation and has been implicated in causing inflammation causing human diseases, such as cancer. The study Neu5Gc is important in evolutionary biology and the development of potential cancer biomarkers. Unfortunately, there are several limitations to detecting Neu5Gc. The elimination of Neu5Gc involves a degradative pathway leading to the incorporation of N-glycolyl groups into glycosaminoglycans (GAGs), such as Gc-CN. Gc-CN has been found in humans and in animals including mice, lamb and chimpanzees. Here, we present the biosynthesis of Gc-CN in bacteria by feeding chemically synthesized N-glycolylglucosamine to Escherichia coli. A metabolically engineered strain of E. coli K4, fed with glucose supplemented with GlcNGc, converted it to N-glycolylgalactosamine (GalNGc) that could then be utilized as a substrate in the chondroitin biosynthetic pathway. The final product, Gc-CN was converted to disaccharides using chondroitin lyase ABC and analyzed by liquid chromatography-tandem mass spectrometry with multiple reaction monitoring detection. This analysis showed the incorporation of GalNGc into the backbone of the chondroitin oligosaccharide.
N-羟乙酰神经氨酸（Neu5Gc）的代谢产物N-羟乙酰软骨素（Gc-CN）是一种唾液酸，常见于哺乳动物而非人类体内。人类可通过食用红肉将外源性Neu5Gc纳入其组织中。由于进化突变，人类无法生物合成Neu5Gc，且它与引发炎症进而导致癌症等人类疾病有关。对Neu5Gc的研究在进化生物学和潜在癌症生物标志物的开发中具有重要意义。不幸的是，检测Neu5Gc存在若干局限性。Neu5Gc的消除涉及一条降解途径，该途径会导致N-羟乙酰基被纳入糖胺聚糖（GAGs），如Gc-CN。在人类以及包括小鼠、羔羊和黑猩猩在内的动物体内均已发现Gc-CN。在此，我们通过向大肠杆菌喂食化学合成的N-羟乙酰葡糖胺，展示了细菌中Gc-CN的生物合成过程。用补充了GlcNGc的葡萄糖喂养的大肠杆菌K4代谢工程菌株，将其转化为N-羟乙酰半乳糖胺（GalNGc），然后GalNGc可作为软骨素生物合成途径中的一种底物被利用。最终产物Gc-CN使用软骨素裂解酶ABC转化为二糖，并通过液相色谱-串联质谱联用多反应监测检测进行分析。该分析表明GalNGc已被纳入软骨素寡糖的主链中。
