Molecular insights into the catalytic mechanism of plasticizer degradation by a monoalkyl phthalate hydrolase

Abstract

Phthalate acid esters (PAEs), a group of xenobiotic compounds used extensively as plasticizers, have attracted increasing concern for adverse effects to human health and the environment. Microbial degradation relying on PAE hydrolases is a promising treatment. However, only a limited number of PAE hydrolases were characterized to date. Here we report the structures of MehpH, a monoalkyl phthalate (MBP) hydrolase that catalyzes the reaction of MBP to phthalic acid and the corresponding alcohol, in apo and ligand-bound form. The structures reveal a positively-charged catalytic center, complementary to the negatively-charged carboxyl group on MBP, and a penetrating tunnel that serves as exit of alcohol. The study provides a first glimpse into the enzyme-substrate binding model for PAE hydrolases, leading strong support to the development of better enzymes in the future.

Phthalate acid ester hydrolases are of promise for the microbial degradation of phthalate acid ester plasticizers, however, only a small number of PAE hydrolases have been characterized. Here, the authors report the structural and functional characterization of MehpH, a monoalkyl phthalate (MBP) hydrolase that degrades MBP to phthalic acid and butanol.