title: Biochemistry of mitochondrial nitric-oxide synthase.
abstract: We reported that the generation of nitric oxide by mitochondria is catalyzed by a constitutive, mitochondrial nitric-oxide synthase (mtNOS). Given that this production may establish the basis for a novel regulatory pathway of energy metabolism, oxygen consumption, and oxygen free radical production, it becomes imperative to identify unequivocally and characterize this enzyme to provide a basis for its regulation. The mitochondrial localization of mtNOS was supported by following the hepatic distribution of mtNOS, immunoblotting submitochondrial fractions, and immunohistochemistry of liver tissues. mtNOS was identified as brain NOS alpha by various methods (mass spectrometry of proteolytic fragments, amino acid analysis, molecular weight, pI, and analysis of PCR fragments), excluding the occurrence of a novel isoform or other splice variants. Distribution of mtNOS transcript indicated its occurrence in liver, brain, heart, muscle, kidney, lung, testis, and spleen. In contrast to brain NOS, mtNOS has two post-translational modifications: acylation with myristic acid and phosphorylation at the C terminus. The former modification is a reversible and post-translational process, which may serve for subcellular targeting or membrane anchoring. The latter modification could be linked to enzymatic regulation. These results are discussed in terms of the role that nitric oxide may have in cellular bioenergetics.
authors.affiliation: Department of Chemistry, University of Minnesota, Duluth, Minnesota 55812, USA.
authors.forename: Sarah Liv
authors.initials: SL
authors.lastname: Elfering
authors.forename: Theresa Marie
authors.initials: TM
authors.lastname: Sarkela
authors.forename: Cecilia
authors.initials: C
authors.lastname: Giulivi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003576:Electron Transport Complex IV / Q000378:metabolism; D022781:Hepatocytes / Q000166:cytology; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D011499:Protein Processing, Post-Translational; D051381:Rats; D017208:Rats, Wistar; D016415:Sequence Alignment; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014018:Tissue Distribution
chemical_list: D007527:Isoenzymes; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D003576:Electron Transport Complex IV