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Reaction Mechanism of Low-Spin Iron(III)- and Cobalt(III)-Containing Nitrile Hydratases: A Quantum Mechanics Investigation
journal contribution
posted on 2017-10-23, 18:03 authored by Mario Prejanò, Tiziana Marino, Carmen Rizzuto, Josè Carlos Madrid Madrid, Nino Russo, Marirosa ToscanoTo
elucidate the catalytic mechanism of cobalt(III)–benzonitrile
and iron(III)–-pivalonitrile hydratases, we have performed
at density functional level a study using the cluster model approach.
Computations were made in a protein framework. Following the suggestions
given in a recent work on the analogous enzyme Fe(III)–NHase,
we have explored the feasibility of a new working mechanism of examined
enzymes. According to our results, after the formation of enzyme substrate
complex, the reaction evolves toward product in only three steps.
The first one is the nucleophilic attack, led by the −OH group
of the αCys113–S–OH on the nitrile carbon atom,
followed by the amide formation and by the enzyme restoring phase
that our computations indicate as the most expensive step from the
energetic point of view in both catalytic processes.