College of Life Sciences, Hebei Basic Science Center for Biotic Interaction, Hebei University, Baoding 071002, China.
Int J Mol Sci. 2024 Aug 15;25(16):8871. doi: 10.3390/ijms25168871.
Polyacrylamide (PAM) is a high-molecular-weight polymer with extensive applications. However, the inefficient natural degradation of PAM results in environmental accumulation of the polymer. Biodegradation is an environmentally friendly approach in the field of PAM treatment. The first phase of PAM biodegradation is the deamination of PAM, forming the product poly(acrylic acid) (PAA). The second phase of PAM biodegradation involves the cleavage of PAA into small molecules, which is a crucial step in the degradation pathway of PAM. However, the enzyme that catalyzes the degradation of PAA and the molecular mechanism remain unclear. Here, a novel monooxygenase PCX02514 is identified as the key enzyme for PAA degradation. Through biochemical experiments, the monooxygenase PCX02514 oxidizes PAA with the participation of NADPH, causing the cleavage of carbon chains and a decrease in the molecular weight of PAA. In addition, the crystal structure of the monooxygenase PCX02514 is solved at a resolution of 1.97 Å. The active pocket is in a long cavity that extends from the C-terminus of the TIM barrel to the protein surface and exhibits positive electrostatic potential, thereby causing the migration of oxygen-negative ions into the active pocket and facilitating the reaction between the substrates and monooxygenase PCX02514. Moreover, Arg10-Arg125-Ser186-Arg187-His253 are proposed as potential active sites in monooxygenase PCX02514. Our research characterizes the molecular mechanism of this monooxygenase, providing a theoretical basis and valuable tools for PAM bioremediation.
聚丙烯酰胺（PAM）是一种高分子量聚合物，具有广泛的应用。然而，PAM 自然降解效率低下，导致聚合物在环境中积累。生物降解是 PAM 处理领域的一种环保方法。PAM 生物降解的第一阶段是 PAM 的脱氨作用，形成产物聚丙烯酸（PAA）。PAM 生物降解的第二阶段涉及 PAA 断裂成小分子，这是 PAM 降解途径中的关键步骤。然而，催化 PAA 降解的酶和分子机制仍不清楚。在这里，鉴定出一种新型单加氧酶 PCX02514 是 PAA 降解的关键酶。通过生化实验，单加氧酶 PCX02514 在 NADPH 的参与下氧化 PAA，导致碳链断裂和 PAA 分子量降低。此外，还解析了单加氧酶 PCX02514 的晶体结构，分辨率为 1.97 Å。活性口袋位于从 TIM 桶的 C 末端延伸到蛋白质表面的长腔中，呈现正静电势，从而导致氧负离子向活性口袋迁移，并促进底物与单加氧酶 PCX02514 之间的反应。此外，提出 Arg10-Arg125-Ser186-Arg187-His253 是单加氧酶 PCX02514 中的潜在活性位点。我们的研究阐明了这种单加氧酶的分子机制，为 PAM 生物修复提供了理论基础和有价值的工具。
