Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Co- and Ru-substituted derivatives of adrenal iron-sulfur protein (adrenodoxin) were prepared from its apoprotein in the presence of urea, dithiothreitol, Na2S, and metal ions. Both metal-substituted proteins had 2 g-atoms each of metal and labile sulfur per mole of protein. The Co derivative had optical absorption maxima at 257, 264, 470, and 1430 nm with shoulders at 275, 280, 300, and 380 nm. The molar extinction coefficient per Co atom was 2.200 M-1 cm-1 at 470 nm. The Ru derivative had a broad maximum at 500 nm with a molar extinction coefficient of approximately 100 M-1 cm-1 per Ru atom. The visible chromophore of the Co- and Ru-substituted proteins with mercurials revealed that the saturation levels are 8.6 and 8.4 mol of mercurial/mol of protein. The values agree with that of the native protein within experimental errors. The tyrosyl residue at position 82 displayed a broad anomalous emission at 335 and 331 nm for the Co- and Ru-substituted proteins, respectively, as well as in the case of the native protein. There was no electron paramagnetic resonance signal of the Co derivative in a wide magnetic field at 77 degrees K. Additionally, the Co and Ru derivatives had no enzymatic activity toward NADPH-cytochrome c reduction in the presence of adrenal diaphorase (adrenodoxin reductase). There was no indication that Mn, Ni, Cu, and Os are incorporated into the apoprotein in the presence of urea. Incorporation of Fe into the protein was examined in the presence of Co or Ru. In a system containing both Fe and Ru, Fe was exclusively incorporated into the protein. In contrast to this, the reaction products from a system containing both Fe and Co were found to consist of both Fe and Co derivatives at approximately equimolar quantity.
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PMID:Cobalt and ruthenium replacement for iron in adrenal iron-sulfur protein (adrenodoxin). Preparation and some properties. 23 19

Covalent modification of cytochrome P-450scc (purified from bovine adrenocortical mitochondria) with pyridoxal 5'-phosphate (PLP) was found to cause inhibition of the electron-accepting ability of this enzyme from its physiological electron donor, adrenodoxin, without conversion to the "P-420" form. Reaction conditions leading to the modification level of 0.82 and 2.85 PLP-Lys residues per cytochrome P-450scc molecule resulted in 60% and 98% inhibition, respectively, of electron-transfer rate from adrenodoxin to cytochrome P-450scc (with beta-NADPH as an electron donor via NADPH-adrenodoxin reductase and with phenyl isocyanide as the exogenous heme ligand of the cytochrome). It was found that covalent PLP modification caused a drastic decrease of cholesterol side-chain cleavage activity when the cholesterol side-chain cleavage enzyme system was reconstituted with native (or PLP-modified) cytochrome P-450scc, adrenodoxin, and NADPH-adrenodoxin reductase. Approximately 60% of the original enzymatic activity of cytochrome P-450scc was protected against inactivation by covalent PLP modification when 20% mole excess adrenodoxin was included during incubation with PLP. Binding affinity of substrate (cholesterol) to cytochrome P-450scc was found to be increased slightly upon covalent modification with PLP by analyzing a substrate-induced spectral change. The interaction of adrenodoxin with cytochrome P-450scc in the absence of substrate (cholesterol) was analyzed by difference absorption spectroscopy with a four-cuvette assembly, and the apparent dissociation constant (Ks) for adrenodoxin binding was found to be increased from 0.38 microM (native) to 33 microM (covalently PLP modified).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of electron transfer from adrenodoxin to cytochrome P-450scc by chemical modification with pyridoxal 5'-phosphate: identification of adrenodoxin-binding site of cytochrome P-450scc. 281 41

Highly purified cytochrome P-450 11 beta-/18-hydroxylase and the electron carriers adrenodoxin and adrenodoxin reductase were prepared from porcine adrenal. When the enzyme was incubated with the electron carriers, 11-deoxycorticosterone (DOC) and NADPH, the following products were isolated and measured by HPLC: corticosterone, 18-hydroxy-11-deoxycorticosterone (18-hydroxyDOC), 18-hydroxycorticosterone and aldosterone. All of the DOC consumed by the enzyme can be accounted for by the formation of these four steroids. Aldosterone was identified by mass spectroscopy and by preparing [3H]aldosterone from [3H]corticosterone followed by recrystallization at constant specific activity after addition of authentic aldosterone. Corticosterone and 18-hydroxycorticosterone were also converted to aldosterone. Conversion of corticosterone and 18-hydroxycorticosterone to aldosterone required P-450, both electron carriers, NADPH and substrate. The reaction is inhibited by CO and metyrapone. Moreover, all three activities of the purified enzyme decline at the same rate when the enzyme is kept at room temperature for various periods of time and when the enzyme is treated with increasing concentrations of anti-11 beta-hydroxylase (IgG) before assay. It is concluded that cytochrome P-450 11 beta-/18-hydroxylase can convert DOC to aldosterone via corticosterone and 18-hydroxycorticosterone. The stoichiometry of this conversion was found to be 3 moles of NADPH, 3 moles of H+ and 3 moles of oxygen per mole of aldosterone produced.
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PMID:Conversion of 11-deoxycorticosterone and corticosterone to aldosterone by cytochrome P-450 11 beta-/18-hydroxylase from porcine adrenal. 338 33

We report here the isolation and partial characterization of a flavoprotein, NADPH-cytochrome P450 (cytochrome c) reductase. The enzyme is a part of steroid 11 alpha-hydroxylating system and is associated with the microsomal fraction of the fungus Rhizopus nigricans. Fungal reductase was solubilized from microsomal membranes with Triton X-100 and purified to apparent homogeneity by affinity and high-performance ion-exchange chromatography. A 350-fold purification of the enzyme with specific activity of 37 mumol cytochrome c reduced/min/mg protein was achieved. A single protein band was obtained on SDS-PAGE analysis with an apparent molecular weight of 79 kDa. Purified reductase contained approximately equimolar quantities of flavin adenine dinucleotide and flavin mononucleotide per mole of the enzyme. Upon induction of the steroid hydroxylating system with progesterone the activity of microsomal NADPH-cytochrome c (P450) reductase increased 10-fold. This is in good correlation with the increase in content of fungal cytochrome P450. Purified fungal flavoprotein was active in a reconstituted system with cytochrome P450 C21 from adrenal gland but could not replace adrenodoxin reductase in the mitochondrial steroid 11 beta-hydroxylating system. We were able to confirm the role of the enzyme by reconstituting steroid 11 alpha-hydroxylating activity from the separated components NADPH-cytochrome P450 reductase and cytochrome P450, partly purified from fungal microsomes.
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PMID:Purification and characterization of NADPH-cytochrome P450 reductase from filamentous fungus Rhizopus nigricans. 973 72