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Summer Research Fellowship Programme of India's Science Academies

Aerobic Acetylene Hydratase: A model study based on DFT level of calculation

Shivam Kumar

Integrated Science Education and Research Centre, Visva Bharati, Santiniketan, West Bengal, India

Sabyasachi Sarkar

Nano Science and Synthetic Leaf Laboratory at Downing Hall, Centre for Healthcare Science and Technology, Indian Institute of Engineering Science and Technology, Howrah, India

Abstract

Traditionally, Acetylene is a known inhibitor of microbial processes by its interaction with metal sites of metalloenzymes such as nitrogenase. However, the first incident to find a bacteria that grows only on acetylene as sole source of carbon and energy dated back to 19791. Later2 it was found that Acetylene Hydratase (AH) activity while growing a bacteria on acetylene in the presence of water by anaerobic fermentation. Further, the presence of CO2 was detected in enrichment cultures from estuarine sediments. An ecological cycle of the primordial world based on further dismutation of acetaldehyde into ethanol and acetate and was proposed3. The purification and characterization of AH enzyme obtained from Palobacter acetylinicus was shown to be a tungsten-Iron-Sulfur Protein4. However, in other strains MoAcy1, TueAcy1 anaerobic growth was seen in the presence of molybdenum based enzyme instead of tungsten5. The Acetylene Hydratase (AH-Mo) when the Tungsten (W) central metal center is exchanged with Molybdenum (Mo) showed lower activity than AH (W), but this new AH (Mo) presence enables the reaction propagation even in the presence of dioxygen6. Through the present work, we are looking into the model chemistry of this aerobic Acetylene Hydratase (Mo) enzyme. Our goal here is to reproduce spectroscopic results of [MoO(mnt)2]-2 7 and to do DFT studies on the mechanism of this reaction, It involves simulations and optimization of the intermediate structures of this multi-step reaction (the hydration of acetylene to acetaldehyde) as well as to explore the structures and geometry of transition states.

Keywords: Acetylene Hydratase, DFT, energetics, [MoO(mnt)2]

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