Urea decomposition facilitated by a urease model complex: a theoretical investigation

Area of Science:

• Biochemistry
• Computational Chemistry
• Inorganic Chemistry

Background:

• Urease enzymes are crucial for the urea cycle, catalyzing urea hydrolysis.
• Understanding the mechanism of urea degradation is vital for biological and industrial applications.
• Nickel-containing complexes serve as models for active sites in metalloenzymes like urease.

Purpose of the Study:

• To elucidate the reaction mechanism of urea degradation by a specific nickel-biimidazole complex.
• To investigate the role of the dinuclear nickel center and bridging ligands in urea transformation.
• To identify the key intermediates and transition states in the catalytic pathway.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model the reaction.
• The potential energy surface for urea degradation was explored.
• Key mechanistic steps, including coordination, proton transfer, and product formation, were analyzed.

Main Results:

• The lowest energy pathway for urea degradation was identified.
• Urea coordination to a nickel center initiates the process.
• Protonation by a bridging water ligand and deprotonation by a bridging hydroxide ligand are critical steps.
• The formation of ammonium cyanate from a bound, disproportionated urea intermediate was observed.

Conclusions:

• The dinuclear nickel complex effectively models urease activity in urea degradation.
• A detailed elimination mechanism converting urea to ammonium cyanate was elucidated.
• The findings provide insights into the catalytic function of nickel-dependent enzymes.