Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.6.5.2 (NQO1)
 6,196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Vitamin K-dependent carboxylase activity has been demonstrated in the crude microsomal fraction of the intima of bovine aortae. The procedure for the isolation of vessel wall carboxylase is a slight modification of the general preparation procedure for tissue microsomes. The highest activity of the non-hepatic enzyme was observed at 25 degrees C and hardly any NADH-dependent vitamin K reductase could be demonstrated. The optimal reaction conditions for both vessel wall as well as liver carboxylase were similar: 0.1 M-NaCl/0.05 M-Tris/HCl, pH 7.4, containing 8 mM-dithiothreitol, 0.4% 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulphonic acid (CHAPS), 0.4 mM-vitamin K hydroquinone and 2 M-(NH4)2SO4. Warfarin inhibits the hepatic and non-hepatic carboxylase/reductase enzyme complex more or less to a similar degree. We have measured the apparent Km values for the following substrates: Phe-Leu-Glu-Glu-Leu ('FLEEL'), decarboxylated osteocalcin, decarboxylated fragment 13-29 from descarboxyprothrombin and decarboxylated sperm 4-carboxyglutamic acid-containing (Gla-)protein. The results obtained demonstrated that liver and vessel wall carboxylase may be regarded as isoenzymes with different substrate specificities. The newly discovered enzyme is the first vitamin K-dependent carboxylase which shows an absolute substrate specificity: FLEEL and decarboxylated osteocalcin were good substrates for vessel wall carboxylase, but decarboxylated fragment 13-29 and decarboxylated sperm Gla-protein were not carboxylated at all.
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PMID:Isolation and partial characterization of a vitamin K-dependent carboxylase from bovine aortae. 349 40

Activity staining with NADPH-nitroblue tetrazolium after native-PAGE of membrane proteins of Synechocystis PCC6803, solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), revealed four NAD(P)H dehydrogenase (NDH) activities; an NDH complex of the respiratory chain, a ferredoxin NADP+ reductase (FNR), a drgA product which oxidized both NADH and NADPH, and an uncharacterized NADH-specific enzyme. The NDH complex was purified with anion exchange and gel filtration chromatographies. The purified complex had a molecular mass of 376 kDa and was composed of 9 subunits. Western analysis showed that the complex contained the NDH-H subunit, but not NDH-A or B. The enzyme reduced ferricyanide much faster than plastoquinone and used NADPH as its preferred electron donor rather than NADH. The enzymatic activity was inhibited by diphenyleneiodonium chloride and salicylhydroxamic acid, but not by rotenone, p-chloromercuribenzoate, N-ethylmaleimide, flavon, dicumarol, or antimycin A. These results suggest that the purified complex is a hydrophilic subcomplex which contains an NADPH binding site and flavin, and is dissociated from a hydrophobic subcomplex, which contains quinone binding site.
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PMID:Properties of the respiratory NAD(P)H dehydrogenase isolated from the cyanobacterium Synechocystis PCC6803. 958 24

The structural and kinetic analyses of the components of the lactate shuttle from heterotrophic Euglena gracilis were carried out. Mitochondrial membrane-bound, NAD(+)-independent d-lactate dehydrogenase (d-iLDH) was purified by solubilization with CHAPS and heat treatment. The active enzyme was a 62-kDa monomer containing non-covalently bound FAD as cofactor. d-iLDH was specific for d-lactate and it was able to reduce quinones of different redox potential values. Oxalate and l-lactate were mixed-type inhibitors of d-iLDH. Mitochondrial l-iLDH also catalyzed the reduction of quinones, but it was inactivated during the extraction with detergents. Both l-iLDH and d-iLDH were inhibited by the specific flavoprotein-inhibitor diphenyleneiodonium, suggesting that l-iLDH was also a flavoprotein. Affinity chromatography revealed that the E. gracilis cytosolic fraction contained two types of NAD(+)-dependent LDH specific for the generation of d- and l-lactate (d-nLDH and l-nLDH, respectively). These two enzymes were tetramers of 126-132 kDa and showed an ordered bi-bi kinetic mechanism. Kinetic properties were different in both enzymes. Pyruvate reduction by d-nLDH was inhibited by its two products; the d-lactate oxidation was 40-fold lower than forward reaction. l-lactate oxidation by l-nLDH was not detected, whereas pyruvate reduction was activated by fructose-1, 6-bisphosphate, K(+) or NH(4)(+). Interestingly, membrane-bound l- and d-lactate dehydrogenases with quinone reductase activity have been only detected in bacteria, whereas the activity of soluble d-nLDH has been identified in bacteria and some yeast. Also, FBP-activated l-nLDH has been found solely in lactic bacteria. Based on their similar kinetic and structural characteristics, a possible common origin among bacterial and E. gracilis lactic dehydrogenase enzymes is discussed.
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PMID:The bacterial-like lactate shuttle components from heterotrophic Euglena gracilis. 1611 76