A Density Functional Theory Investigation of Cleavage Mechanism of Dimethylsulphoniopropionate by Lyase DddQ

Abstract

Dimethylsulfide (DMS) is released from the dimethylmercaptopropionate (DMSP) lyase decomposition reaction, which is of great significance for the global sulfur cycle. Among the various DMSP lyases, DddQ is one of the most prevalent and effective enzymes, catalyzing the conversion of DMSP into DMS. Using density functional calculations, we performed a detailed investigation of the DddQ reaction employing a concerted β-elimination mechanism via Tyr131 or Tyr120 as a general base. The reaction involves several key processes, including the deprotonation of nucleophile base, hydrogen proton transfer on Cα, and Cβ-S bond cleavage. Notably, the Hα proton transfer step is a critical step in determining the reaction rate in both mechanisms.