Alhasawi Azhar, Thomas Sean C, Appanna Vasu D
Faculty of Science and Engineering, Laurentian University, Sudbury, ON P3E2C6, Canada.
Faculty of Science and Engineering, Laurentian University, Sudbury, ON P3E2C6, Canada.
Enzyme Microb Technol. 2016 Apr;85:51-6. doi: 10.1016/j.enzmictec.2016.01.007. Epub 2016 Jan 21.
Glycerol is a major by-product of the biodiesel industry. In this study we report on the metabolic networks involved in its transformation into pyruvate, phosphoenolpyruvate (PEP) and ATP. When the nutritionally-versatile Pseudomonas fluorescens was exposed to hydrogen peroxide (H2O2) in a mineral medium with glycerol as the sole carbon source, the microbe reconfigured its metabolism to generate adenosine triphosphate (ATP) primarily via substrate-level phosphorylation (SLP). This alternative ATP-producing stratagem resulted in the synthesis of copious amounts of PEP and pyruvate. The production of these metabolites was mediated via the enhanced activities of such enzymes as pyruvate carboxylase (PC) and phosphoenolpyruvate carboxylase (PEPC). The high energy PEP was subsequently converted into ATP with the aid of pyruvate phosphate dikinase (PPDK), phosphoenolpyruvate synthase (PEPS) and pyruvate kinase (PK) with the concomitant formation of pyruvate. The participation of the phospho-transfer enzymes like adenylate kinase (AK) and acetate kinase (ACK) ensured the efficiency of this O2-independent energy-generating machinery. The increased activity of glycerol dehydrogenase (GDH) in the stressed bacteria provided the necessary precursors to fuel this process. This H2O2-induced anaerobic life-style fortuitously evokes metabolic networks to an effective pathway that can be harnessed into the synthesis of ATP, PEP and pyruvate. The bioconversion of glycerol to pyruvate will offer interesting economic benefit.
甘油是生物柴油行业的一种主要副产品。在本研究中，我们报告了参与将其转化为丙酮酸、磷酸烯醇式丙酮酸（PEP）和三磷酸腺苷（ATP）的代谢网络。当营养多样的荧光假单胞菌在以甘油为唯一碳源的矿物培养基中暴露于过氧化氢（H2O2）时，该微生物会重新配置其代谢，主要通过底物水平磷酸化（SLP）来生成三磷酸腺苷（ATP）。这种替代性的ATP生成策略导致了大量PEP和丙酮酸的合成。这些代谢物的产生是通过丙酮酸羧化酶（PC）和磷酸烯醇式丙酮酸羧化酶（PEPC）等酶活性的增强介导的。随后，高能PEP在丙酮酸磷酸双激酶（PPDK）、磷酸烯醇式丙酮酸合酶（PEPS）和丙酮酸激酶（PK）的帮助下转化为ATP，并伴随丙酮酸的形成。腺苷酸激酶（AK）和乙酸激酶（ACK）等磷酸转移酶的参与确保了这种不依赖氧气的能量生成机制的效率。应激细菌中甘油脱氢酶（GDH）活性的增加为这一过程提供了必要的前体。这种由H2O2诱导的厌氧生活方式偶然地将代谢网络引向一条有效的途径，该途径可用于合成ATP、PEP和丙酮酸。甘油向丙酮酸的生物转化将带来有趣的经济效益。
