Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: KEGG:D02011 (FAD)
 5,530 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Given that the oxidation of nitroethane by D-amino acid oxidase proceeds through a transient carbinolamine adduct at the N5 position of the active-site FAD cofactor (Porter, D. J. T., Voet, J. G., and Bright, H. J. (1973) J. Biol. Chem. 248, 4400-4416), it follows that 1-chloro-1-nitroethane should generate a stable amide at N5 and thereby function as a suicide inactivator of this enzyme. This hypothesis was validated as follows. 1-Chloro-1-nitroethane, as the nitronate ion (pKa = 7.0), inactivated D-amino acid oxidase completely with a Km value of 2 mM and a maximum rate of 0.02 s-1. The chloro and nitro groups were quantitatively recovered as free Cl- and NO2(-) after the enzyme was inactivated by 1.5 flavin equivalents of 1-chloro-1-nitroethane. Inactivation did not require O2 and was accompanied by bleaching of the flavin under both anaerobic and aerobic conditions. The modified coenzyme of the inactivated enzyme was identified as N5-acetyl-1,5-dihydro FAD. The enzyme catalyzes the oxidation of 1-chloro-1-nitroethane to acetate approximately 0.5 times as rapidly as the enzyme catalyzes suicide inactivation. The transient intermediate which is common to both the inactivation and oxidation pathways must be N5-(1-X-1-hydroxyethyl)-1,5-dihydro FAD, where X = nitro or chloro.
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PMID:Suicide inactivation of D-amino acid oxidase by 1-chloro-1-nitroethane. 613 86

Intact mitochondria isolated from Nicotiana tabacum cv. Bright Yellow 2 (TBY-2) cells can take up riboflavin via carrier-mediated systems that operate at different concentration ranges and have different uptake efficiencies. Once inside mitochondria, riboflavin is converted into catalytically active cofactors, FMN and FAD, due to the existence of a mitochondrial riboflavin kinase (EC 2.7.1.26) and an FAD synthetase (EC 2.7.7.2). Newly synthesized FAD can be exported from intact mitochondria via a putative FAD exporter. The dependence of FMN synthesis rate on riboflavin concentration shows saturation kinetics with a sigmoidal shape (S(0.5), V(max) and Hill coefficient values 0.32+/-0.12 microm, 1.4 nmol x min(-1) x mg(-1) protein and 3.1, respectively). The FAD-forming enzymes are both activated by MgCl(2), and reside in two distinct monofunctional enzymes, which can be physically separated in mitochondrial soluble and membrane-enriched fractions, respectively.
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PMID:The occurrence of riboflavin kinase and FAD synthetase ensures FAD synthesis in tobacco mitochondria and maintenance of cellular redox status. 1904 14