Xiao Tingting, Zhang Dengwei, Tun Hein Min, Shah Nagendra P
Food and Nutritional Science, School of Biological Sciences, The University of Hong Kong, Kadoorie Biological Sciences Building, Pokfulam Road, Hong Kong, China.
HKU-Pasteur Research Pole, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
World J Microbiol Biotechnol. 2022 Aug 16;38(11):185. doi: 10.1007/s11274-022-03379-1.
Levilactobacillus brevis NPS-QW-145 isolated from kimchi is deficient in glutamate dehydrogenase-encoding gene (gdhA) to form glutamate, hence it required exogenous supplementation of glutamate/monosodium glutamate (MSG) for decarboxylation reaction to produce γ-aminobutyric acid (GABA). However, GABA conversion rate from MSG was relatively low. The individual effect of 20 amino acids on regulating GABA biosynthesis was investigated. Cysteine was selected to significantly improve GABA production from MSG. It was found that Lb. brevis was capable of producing HO, cysteine protected Lb. brevis against HO-induced oxidative damage to increase cell viability for the enhancement of GABA production. Moreover, cysteine promoted glucose consumption to produce acetyl-CoA for synthesizing long-chain fatty acids to significantly up-regulate GABA biosynthesis. These findings deciphered antioxidative capability of cysteine in Lb. brevis 145 and provided a theoretical basis for fatty acids synthesis-mediated GABA synthesis in Lb. brevis 145, and possibly in other lactic acid bacteria.
从泡菜中分离出的短乳杆菌Levilactobacillus brevis NPS-QW-145缺乏编码谷氨酸脱氢酶的基因（gdhA），无法合成谷氨酸，因此需要外源添加谷氨酸/味精（MSG）以进行脱羧反应来产生γ-氨基丁酸（GABA）。然而，MSG转化为GABA的比率相对较低。研究了20种氨基酸对调节GABA生物合成的单独作用。结果发现半胱氨酸能显著提高由MSG生成的GABA产量。研究发现短乳杆菌能够产生HO，半胱氨酸可保护短乳杆菌免受HO诱导的氧化损伤，从而提高细胞活力以增强GABA的产量。此外，半胱氨酸促进葡萄糖消耗以产生乙酰辅酶A用于合成长链脂肪酸，从而显著上调GABA的生物合成。这些发现揭示了半胱氨酸在短乳杆菌145中的抗氧化能力，并为短乳杆菌145以及可能在其他乳酸菌中由脂肪酸合成介导的GABA合成提供了理论依据。
