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

The vitamin K-dependent carboxylase extracted from rat liver microsomes by 3-([3-cholamidopropyl] dimethylammoniol)-1-propane sulfonate detergent solution has been partially purified by chromatography on Ultrogel AcA-34 followed by carboxymethyl-Sepharose chromatography and pentapeptide affinity chromatography. The carboxylase appears to be composed of two proteins, the enzyme and endogenous substrate as judged by the incorporation of 14CO2 into trichloroacetic acid insoluble protein. The apparent Km for Phe-Leu-Glu-Glu-Leu as carboxylation substrate is approximately 3 mM. 2,3,5,6-Tetrachloro-4-pyridinol at 10 microM inhibits 90% of the enzyme activity, whereas maximal stimulation (1.7-fold) by pyridoxal 5'-phosphate is obtained at 1 mM and by Mn2+ at 5 mM. The stimulation by pyridoxal 5'-phosphate and by Mn2+ are not additive. The carboxylation of Phe-Leu-Glu-Glu-Leu at 20 degrees C is linear for 90 min. Vitamin K1 plus NADH do not replace vitamin K1 hydroquinone, indicating that vitamin K reductase is not part of this purified carboxylase-substrate complex. Vitamin K epoxidase activity co-elutes with the carboxylase complex. Some 400-fold purification from microsomes has been obtained to yield enzyme preparations with a specific activity of approximately 17,000 pmol of CO2 fixed into peptide/mg of enzyme protein, which is some 15-fold greater than any previously reported enzyme preparation from rat liver microsomes.
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PMID:Vitamin K-dependent carboxylase. Partial purification and properties of the enzyme-substrate complex. 717 81