Structural Basis for the Enzyme-Polymer Binding Mechanism of Poly(vinyl alcohol) Esterase

Structural characterization of microbial enzymes involved in plastic transformation and modification is of significant importance, yet has been hindered by the challenges in obtaining enzyme-plastic complex structures. Poly(vinyl alcohol) (PVA), a typical C–C backbone hydrophilic polymer, offers a potential for obtaining enzyme-polymer complexes. DacApva, a unique PVA deacetylase, was recently identified from PVA utilizer Comamonas sp. strain NyZ500. However, the molecular basis of PVA binding and deacetylation by DacApva remains unknown. Here, we determined high-resolution crystal structures of DacApva and its complex with acetylated PVA. A distinctive hydrophobic platform and enhanced serine interactions were found to be crucial for stable substrate binding in the active site, which differed from the previously reported arginine interactions in this class of enzymes. A plausible model of DacApva was proposed for serine prebinding and the sequential removal of acetyl groups by sliding PVA C–C backbone based on biochemical and computational approaches. Our study presents a valuable framework for investigating the enzymatic deacetylation of C–C backbone polymers and has promising implications for the development of efficient plastic-modifying enzymes.