Document Type
Article
Publication Date
9-1-2013
Publication Title
The FEBS Journal
Abstract
NO synthase (NOS) enzymes convert L-arginine to NO in two sequential reactions whose rates (kcat1 and kcat2) are both limited by the rate of ferric heme reduction (kr). An enzyme ferric heme –NO complex forms as an immediate product complex and then undergoes either dissociation (at a rate that we denote as kd) to release NO in a productive manner, or reduction (kr) to form a ferrous heme –NO complex that must react with O2 (at a rate that we denote as kox) in a NO dioxygenase reaction that regenerates the ferric enzyme. The interplay of these five kinetic parameters (kcat1, kcat2, kr, Kd and kox) determines NOS specific activity, O2 concentration response, and pulsatile versus steady-state NO generation. In the present study, we utilized stopped-flow spectroscopy and single catalytic turnover methods to characterize the individual temperature dependencies of the five kinetic parameters of rat neuronal NOS. We then incorporated the measured kinetic values into computer simulations of the neuronal NOS reaction using a global kinetic model to comprehensively model its temperature dependent catalytic behaviours. The results obtained provide new mechanistic insights and also reveal that the different temperature dependencies of the five kinetic parameters significantly alter neuronal NOS catalytic behaviours and NO release efficiency as a function of temperature.
Recommended Citation
Haque, Mohammad Mahfuzul; Tejero, Jesus; Bayachou, Mekki; Wang, Zhi-Qiang; Fadlalla, Mohammed; and Stuehr, Dennis J., "Thermodynamic Characterization of Five Key Kinetic Parameters That Define Neuronal Nitric Oxide Synthase Catalysis" (2013). Chemistry Faculty Publications. 334.
https://engagedscholarship.csuohio.edu/scichem_facpub/334
DOI
10.1111/febs.12404
Version
Postprint
Publisher's Statement
This is the accepted version of the following article: http://onlinelibrary.wiley.com/doi/10.1111/febs.12404/abstract, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/febs.12404/abstract
Volume
280
Issue
18
Comments
This work was supported by National Institutes of Health Grants GM51491 and HL58883 to D.J.S. We also acknowledge funding by The National Science Founudation to MB (Grant CHE-0848820).