Lung microsomal hydroxylase-characterization and reconstitution of its activity

Arınç, Emel
Aydoǧmuş, Aydan
1. Formation of catechols from benzene and nitrobenzene have been implicated in the carcinogenic activity of these chemicals. In liver, , an intermediate of is enzymatically converted to 4-nitrocatechol. 2. 2. For the first time in this study, the presence of a highly active enzyme catalyzing the formation of 4-nitrocatechol from was detected in lung microsomes. The average specific activity of lung hydroxylase was found to be 0.494 nmol 4-nitrocatechol formed mg prot−1 min−1. 3. 3. The optimum conditions for sheep lung microsomal hydroxylase were established. The maximal activity was noted at pH 6.8. The rate of hydroxylation was linear up to 2 mg prot/ml of incubation mixture. The maximal rate of 4-nitrocatechol formation was observed with 0.25 mM . 4. 4. The Lineweaver-Burk and Eadie-Hofstee plots were found to be curve-linear. Two different values were calculated as 11.6 and 71.4 μM from the Lineweaver-Burk plot and as 10.7 and 74.5 μM from the Eadie-Hofstee plot. This suggested that there were either two forms of enzyme or two different enzymes participating in ortho hydroxylation of in lung microsomes. 5. 5. Lung microsomal hydroxylase activity of sheep was reconstituted in the presence of purified lung microsomal cytochrome P-450, NADPH dependent cytochrome P-450 reductase and synthetic lipid, phosphatidylcholine dilauroyl.
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry


ARINC, E; Güray, Nülüfer Tülün; SAPLAKOGLU, U; Adalı, Orhan (Elsevier BV, 1992-01-01)
1. Two forms of soluble NADH cytochrome b5 reductase were purified from human erythrocytes. Two distinct fractions both having the NADH cytochrome b5 reductase activity eluted from the second DEAE-cellulose column were further purified by ultrafiltration and 5'-ADP-agarose affinity chromatography.
Characterization and modulation by drugs of sheep liver microsomal flavin monooxygenase activity
Demirdöǧen, Birsen Can; Adalı, Orhan (Wiley, 2005-07-01)
The flavin monooxygenases (FMO) catalyse the NADPH and oxygen-dependent oxidation of a wide range of nucleophilic nitrogen-, sulfur-, phosphorus-, and selenium heteroatom-containing chemicals, drugs, and agricultural agents. In the present study, sheep liver microsomal FMO activity was determined by measuring the S-oxidation rate of methimazole and the average specific activity obtained from different microsomal preparations was found to be 3.8 +/- 1.5 nmol methimazole oxidized min(-1) mg(-1) microsomal pro...
The effect of cysteine-43 mutation on thermostability and kinetic properties of citrate synthase from Thermoplasma acidophilum
Kocabıyık, Semra; Russel, RJM; Danson, MJ; Hough, DW (Elsevier BV, 1996-07-05)
In this study, we have substituted serine-43 by cysteine in the recombinant citrate synthase from a moderately thermophilic Archaeon Thermoplasma acidophilum, for site-specific attachment of labels and have investigated the effects of this mutation on the biochemical properties and thermal stability of the enzyme. Both wild-type and the mutant enzymes were purified to homogenity using affinity chromatography on Matrex Gel Red A. The mutant Thermoplasma citrate synthase is very similar to wild-type citrate s...
Alteration of enzyme activities and kinetic properties of GST and NQO1 with naturally occurring phenolic compounds
KARAKURT, SERDAR; Sever, Melike; Celebioglu, Hasan Ufuk; Adalı, Orhan (Walter de Gruyter GmbH, 2015-01-01)
Objective: Glutathione S-transferase (GST) and NAD(P)H:quinine oxidoreductase 1 (NQO1) are the enzymes important in cytoprotection and bioactivation of chemicals. This study has addressed effects of polyphenolic compounds; ellagic acid, quercetin, naringenin, resveratrol, rutin and hesperidin on rabbit liver GST and NQO1 enzyme activities.
Regulation of crystal protein biosynthesis by Bacillus thuringiensis: II. Effects of carbon and nitrogen sources.
Içgen, Y; İçgen, Bülent; Özcengiz, Gülay (Elsevier BV, 2002-11-01)
The regulation of crystal protein production in Bacillus thuringiensis 81 by sources of carbon and nitrogen was investigated. The highest titers of toxin were obtained on sucrose, lactose and inulin which also supported sporulation. Whey and molasses were also potential carbon substrates for toxin production. Other carbohydrates including glucose, glycerol, maltose, starch and dextrin yielded lower amounts of toxin. Nitrogen sources were found to exert the most profound controls. Peptone was the best organi...
Citation Formats
E. Arınç and A. Aydoǧmuş, “Lung microsomal hydroxylase-characterization and reconstitution of its activity,” Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, pp. 455–460, 1990, Accessed: 00, 2020. [Online]. Available: