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Rates of Electron Flux Through Calmodulin – Free Neuronal Nitric Oxide Synthase & NADPH‐Cytochrome P450 Reductase are Equivalent in the Presence of Dinitrobenzenes
Author(s) -
Joshi Chintamani N,
Miller Richard Timothy
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.2_supplement.326
Subject(s) - chemistry , reductase , calmodulin , nitric oxide , electron transport chain , nitric oxide synthase , oxidoreductase , stimulation , cytochrome c , oxidative stress , biochemistry , biophysics , enzyme , mitochondrion , biology , endocrinology , organic chemistry
Dinitrobenzenes (DNBs) are well known environmental pollutants known to redox‐cycle in the presence of NADPH‐cytochrome P450 oxidoreductase (CYPOR). The reductase domain of neuronal nitric oxide synthase (nNOS) mechanistically resembles CYPOR. We compared the electron transfer efficiencies of calmodulin (CaM) – free nNOS (nNOS − )and CYPOR exposed to DNBs. Turnover rates (min −1 ) for NADPH oxidation (NADPH ox ) and acetylated cytochrome‐ c reduction (AcCyt‐ c red ) were used to estimate electron flux and O 2 •− production, respectively. DNBs stimulated NADPH ox by nNOS − ( + imidazole) and CYPOR in an isomer – and concentration – dependent manner. V MAX for NADPH ox by CYPOR (302±9 min −1 ) and nNOS − (230±1 min −1 ) occurred at 80 and 160 μM 1,4‐DNB, respectively. NADPH ox rates by nNOS− were greater than with CYPOR (p < 0.05) from 80 to 160 μM 1,3‐DNB. However, no differences in rates were observed between nNOS − and CYPOR with 1,2‐DNB. A SOD (50 U/ml) inhibitable, DNB – specific and dependent, stimulation of AcCyt‐ c red rates was observed with nNOS− and CYPOR. These results indicate that resting – state nNOS − behaves as an efficient oxidoreductase and efficiently generates O 2 •− in the presence of DNBs. Thus, continuous exposure of humans to low level DNBs may lead to stimulation of O 2 •− production resulting in chronic oxidative stress. Supported by ES011982 and RR008124 to RTM and UTEP, respectively.