Structural Insights into Enzymatic Degradation of Oxidized Polyvinyl Alcohol

Abstract The ever‐increasing production and use of polyvinyl alcohol (PVA) threaten our environment. Yet PVA can be assimilated by microbes in two steps: oxidation and cleavage. Here we report novel α/β‐hydrolase structures of oxidized PVA hydrolase (OPH) from two known PVA‐degrading organisms, Sphingopyxis sp. 113P3 and Pseudomonas sp. VM15C, including complexes with substrate analogues, acetylacetone and caprylate. The active site is covered by a lid‐like β‐ribbon. Unlike other esterase and amidase, OPH is unique in cleaving the CC bond of β‐diketone, although it has a catalytic triad similar to that of most α/β‐hydrolases. Analysis of the crystal structures suggests a double‐oxyanion‐hole mechanism, previously only found in thiolase cleaving β‐ketoacyl‐CoA. Three mutations in the lid region showed enhanced activity, with potential in industrial applications.