Mechanistic Investigations on Bacterial Enzymes from Sulfur Metabolism and Terpene Biosynthesis

Abstract

This cumulative doctoral thesis encompasses six research articles focused on mechanistic investigations of sulfur metabolism and terpene biosynthesis. The primary focus of this research is on enzymes involved in the degradation of sulfur metabolites, which play a critical role in the marine sulfur cycle. A part of this research is about the study of DMSP lyases that facilitate the breakdown of DMSP analogs into compounds with natural flavors. An Interesting contribution of this thesis is the detailed investigation into the degradation of a newly discovered sulfur metabolite, dimethylsulfoxonium propionate (DMSOP) by DMSP lyases. This represents the first comprehensive analysis of how DMSP lyases interact with and break down the DMSOP. Additionally, the research partially investigated the stereoselectivity of DMSP lyases by synthesizing the chiral DMSOP analogs. This aspect of the study highlights the DMSP lyases ability to distinguish and act upon different stereoisomers. <br /> Another key enzyme explored in this thesis is DmdC, which plays an important role in the DMSP demethylation pathway. The lack of a crystal structure for DmdC together with its substrate poses a significant challenge to understanding its catalytic mechanism. To address this, deuterium-labeled isotopomers were synthesized, enabling detailed stereochemical investigations. In addition to sulfur metabolism, this thesis also explores terpene biosynthesis. It shows the isolation and characterization of the first bacterial enzymes capable of synthesizing sesquiterpenes, including (+)-α-cadinene, (+)-δ-cadinol, and (-)-amorpha-4,11-diene. <br /> All in all, this thesis provides a comprehensive and detailed investigations of sulfur metabolism and terpene biosynthesis. It advances the understanding of the enzymatic processes involved in these essential biochemical pathways, offering new insights into the natural mechanisms that drive these reactions.