Mechanism and kinetics of inducible nitric oxide synthase auto-S-nitrosation and inactivation. Biochemistry 2012 Feb 07;51(5):1028-40
Date
01/17/2012Pubmed ID
22242685Pubmed Central ID
PMC3277664DOI
10.1021/bi201818cScopus ID
2-s2.0-84863406254 (requires institutional sign-in at Scopus site) 33 CitationsAbstract
Nitric oxide (NO), the product of the nitric oxide synthase (NOS) reaction, was previously shown to result in S-nitrosation of the NOS Zn(2+)-tetrathiolate and inactivation of the enzyme. To probe the potential physiological significance of NOS S-nitrosation, we determined the inactivation time scale of the inducible NOS isoform (iNOS) and found it directly correlates with an increase in the level of iNOS S-nitrosation. A kinetic model of NOS inactivation in which arginine is treated as a suicide substrate was developed. In this model, NO synthesized at the heme cofactor is partitioned between release into solution (NO release pathway) and NOS S-nitrosation followed by NOS inactivation (inactivation pathway). Experimentally determined progress curves of NO formation were fit to the model. The NO release pathway was perturbed through addition of the NO traps oxymyoglobin (MbO(2)) and β2 H-NOX, which yielded partition ratios between NO release and inactivation of ~100 at 4 μM MbO(2) and ~22000 at saturating trap concentrations. The results suggest that a portion of the NO synthesized at the heme cofactor reacts with the Zn(2+)-tetrathiolate without being released into solution. Perturbation of the inactivation pathway through addition of the reducing agent GSH or TCEP resulted in a concentration-dependent decrease in the level of iNOS S-nitrosation that directly correlated with protection from iNOS inactivation. iNOS inactivation was most responsive to physiological concentrations of GSH with an apparent K(m) value of 13 mM. NOS turnover that leads to NOS S-nitrosation might be a mechanism for controlling NOS activity, and NOS S-nitrosation could play a role in the physiological generation of nitrosothiols.
Author List
Smith BC, Fernhoff NB, Marletta MAAuthor
Brian C. Smith PhD Associate Professor in the Biochemistry department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsArginine
Biotin
Catalysis
Down-Regulation
Mice
Models, Molecular
Nitric Oxide
Nitric Oxide Synthase Type II
Nitrosation
S-Nitrosoglutathione
Substrate Specificity
