Fast ferrous heme–NO oxidation in nitric oxide synthases.

Tejero, Jesús; Santolini, Jérôme; Stuehr, Dennis J.

During catalysis, the heme in nitric oxide synthase (NOS) binds NO before releasing it to the environment. Oxidation of the NOS ferrous heme–NO complex by O2 is key for catalytic cycling, but the mechanism is unclear. We utilized stopped-flow methods to study the reaction of O2 with ferrous heme–NO complexes of inducible and neuronal NOS enzymes. We found that the reaction does not involve heme–NO dissociation, but instead proceeds by a rapid direct reaction of O2 with the ferrous heme–NO complex. This behavior is novel and may distinguish heme–thiolate enzymes, such as NOS, from related heme proteins.

NITRIC oxide; PROTEINS; ENZYMES; NUCLEAR reactions; TETRAPYRROLES; HEMOPROTEINS; FLOW injection analysis

FEBS Journal, 2009, Vol 276, Issue 16, p4505

1742-464X

Academic Journal

10.1111/j.1742-4658.2009.07157.x