Interactions between acetylenic compounds and a synthesized tungsten(IV) model complex : implications to the reaction mechanism of acetylene hydratase

Abstract

Tungsten is the only known 3rd row transition metal currently found in metalloenzymes; all tungsten metalloenzymes known to date are primarily found in anaerobic, thermophilic bacteria and hyperthermophilic archaea. Mononuclear tungsten and molybdenum metalloenzymes contain a sulfur-rich coordination sphere composed of at least one pyranopterindithiolate cofactor, chalcogen donors, and a protein-bound amino acid. Acetylene hydratase is a tungstoenzyme that catalyzes a net nonredox reaction, the hydration of acetylene to acetaldehyde. Acetylene hydratase (AH) is unique in that it is the only known enzyme to use acetylene as its native substrate and as the sole carbon source for these organisms. Chemical routes to the hydration of acetylene are known, but the mechanism of AH is not fully understood. The purpose of this research was to gain a better understanding of the reaction mechanism of AH by experimentally determining the interaction between acetylenic compounds and a synthesized W(IV) model complex.