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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The effect of feeding with a diet containing 0.2% (w/w) hexachlorobenzene on hepatic and urinary porphyrins and hepatic cytochrome P-450 was studied at various time intervals in female Wistar rats. 2. Hexachlorobenzene administration for 45 days resulted in the development of porphyria in rats, which biochemically closely resembles symptomatic porphyria in humans, with elevation of urinary uroporphyrin excretion, hepatic uroporphyrin content, and hepatic cytochrome P-450 content, in addition to appearance of porphyrins of the isocoproporphyrin (P1) series in the faeces. 3. Spectral studies of the induced hepatic cytochrone P-450 at 45 days with carbon monoxide and ethyl isocyanide as ligands indicated the presence of a greater admixture of a haemoprotein distinct from cytochrome P-450. 4. Study in vitro of the kinetics of two reactions, namely aminopyrine N-demethylation and 3,4-benzpyrene hydroxylation, catalysed by the hepatic microsomal cytochrom P-450-dependent enzyme system, suggested that hexachlorobenzene induced a form of cytochrome P-450-dependent enzyme system, suggested that hexachlorobenzene induced a form of cytochrome P-450 with different catalytic properties from those of forms induced by either phenobarbital or 3-methylcholanthrene.
Clin Sci Mol Med 1978 Nov
PMID:The nature of hepatic cytochrone P-450 induced in hexachlorobenzene-fed rats. 71 99

Energy dependent calcium binding in microsomal vesicles from the longitudinal smooth muscle of the guinea pig intestine was investigated at two different temperatures (30 degrees C and 10 degrees C) and in the absence and presence of CdCl2, BaCl2 and MnCl2. The investigation was carried out to determine whether the effects of temperature and the effects of the divalent ions on microsomal calcium binding could be correlated with the effects of these interventions on the mechanical activity of the intact longitudinal fibers. A reduction in temperature from 30 degrees C to 10 degrees C inhibited both the uptake of calcium into the microsomes and the rate of release of calcium ions from the microsomes to the external medium. This exchange in temperature also slowed the rate of relaxation of the intact longitudinal muscle after it had been induced to contract with acetylcholine and subsequently allowed to relax by removing calcium ions from the bathing medium and adding 1 X 10(-3) M EGTA. The presence of CdCl2, like the reduction in temperature, decreased the uptake of calcium into the microsomal vesicles. However, the release of calcium from the microsomes was accelerated. BaCl2, produced the same effects as did CdCl2 on the uptake of calcium into microsomes but to a lesser extent. It had very little effect on the release of calcium ions from the microsomes. MnCl2 had no significant effects on either the uptake or release of calcium ions in the microsomal preparation. Both CdCl2 and MnCl2 exerted an inhibitory action on acetylcholine-induced contractile responses of the intact longitudinal fibers; whereas BaCl2 served to initiate a contractile response in the smooth muscle fibers. Thus, it would appear that the effects of a temperature change on microsomal calcium binding and on mechanical activity in intact fibers can be correlated; but the effects of CdCl2, BaCl2 and MnCl2 on these two cellular processes do not follow any consistent pattern.
Mol Cell Biochem 1975 Jul 31
PMID:Effects of temperature and inorganic ions on calcium accumulation in microsomes from intestinal smooth muscle. 80 67

1. Mitochondria and microsomal fractions have been isolated from liver biopsies from patients with alcoholic cirrhosis, cryptogenic cirrhosis or chronic aggressive hepatitis. 2. Cirrhotic livers yieled fewer mitochondria than normal liver. 3. The most significant change was a decrease in mitochondrial respiratory control. Cirrhotic microsomal fractions had a 50% diminution in cytochrome b5 and cytochrome P-450 content. 4. The two patients with chronic aggressive hepatitis showed similar mitochondrial and microsomal changes.
Clin Sci Mol Med 1977 Jun
PMID:Mitochondrial functions and content of microsomal and mitochondrial cytochromes in human cirrhosis. 88 31

Several problems regarding the protein acceptor of the oligosaccharide from GEA (glucosylated endogenous acceptor) were investigated in the present work using rat liver microsomal subfractions. It was found that the acceptor molecule is present in rough and smooth liver microsomes. Furthermore both fractions have closely similar specific activities. The problem of whether nascent peptides must be ribosome bound for glycosylation to occur was studied. The results suggests that binding of peptides to ribosomes is not a necessary condition for the transfer of GEA oligosaccharide to protein. The increase in specific activity found after partial release of the microsomal vesicular content suggests that the acceptor protein for GEA is membrane bound. Evidence obtained in attempting to elucidate whether nascent or completed chains are glycosylated favours the later possibility.
Mol Cell Biochem 1977 Jul 05
PMID:Glycosylation of endogenous protein(s) of the rough and smooth microsomes by a lipid sugar intermediate. 88 88

1. From different studies on the cellular localization, postional specificity, and regulatory properties of acyl-CoA: glycerophosphate acyltransferase (EC 2,3,1.15) AND ACYL-CoA: 1-ACYLGLYCEROPHOSPHATE ACYLTRANSFERASE (EC 2,3,1....) the following conclusions can be drawn: The glycerophosphate acyltransferase is localized in the endoplasmatic reticulum (microsomes) and in the outer membrane of the mitochondria of the animal cell. Its reaction product is 1-acylglycerophosphate (1-lysophosphatidic acid). The mitochondrial enzyme shows a high preference for saturated fatty acids while the microsomal enzyme is less specific (alternatively the microsomes contain more than one glycerophsophate acyltransferase). 2. The 1-acylglycerphosphate acyltransferase is localized in the endoplasmatic reticulum (microsomes) in the animal cell. Possibly a minor fraction of this enzyme is localized to the outer membrane of the mitochondria. This enzyme shows a strong preference for unsaturated fatty acids. 3. Both the microsomal and the mitochondrial dihydroxyacetonephosphate acyltransferase show similar fatty acid specificity as the corresponding glycerophosphate acyltransferases. It cannot be excluded that dihydroxy-acetonephosphate and glycerophosphate are acylated by the same enzymes. 4. The activity of the glycerophosphate acyltransferase(s) in the liver decreases in fasting or fat feeding and increases upon feeding of carbohydrate. The activity of carnitine palmityltransferase varies exacty opposit. These enzymes do not show dietary variations in heart and adipose tissue. 5. Under the otherwise identical conditions the rate of carnitine acylation in isolated mitochondria decreases more than the rate of glycerophosphate acylation when the concentration of palmityl-CoA is reduced. 6. In isolated liver cells (which has lost most of their carnitine) addition of carnitine increases the rate of fatty acid oxidation and decreases the rate of triglyceride formation. 7. Glycerol and fructose lower the rate of fatty acid oxidation, probably by lowering the levels of acyl-CoA and acyl-carnitine in the cells. 8. It is concluded that the relative activities of glycerophosphate acyltranse and carnitine palmityltransferase probably influence the fate of fatty acids in the cell.
Mol Cell Biochem 1976 Aug 30
PMID:The glycerophosphateacyltransferases and their function in the metabolism of fatty acids. 95 14

Two approaches may be used to study the function of cytochrome P-450 in insects: (a) an evaluation of the spectral and catalytic properties of the hemoprotein while associated with microsomal membranes; (b) the solubilization, resolution and purification of the microsomal mixed-function oxidase system. The first approach has provided some understanding of the biochemical factors involved in the metabolism of a variety of compounds, including pesticides, drugs, hormones and many other xenobiotics. However, solubilization of the monooxygenase system allows the study of each of its components individually, providing a better insight on the sequence of events leading to the hydroxylation of a substrate, the type of intermediates formed, and the rate-limiting step(s). This report discusses studies carried out with the monooxygenase system associated with microsomal membranes, as well as procedures to solubilize and partially purify its components from housefly microsomes. The latter involves solubilization with either Triton X-100 or sodium cholate, followed by either ammonium sulfate fractionation, Sephadex G-200, DEAE-Sephadex A-50 column chromatography or by omega-amino-n-octyl-Sepharose 4B affinity chromatography. These procedures have shown that two cytochrome P-450 species (P-450 and P-450I) are present in microsomes isolated from a resistant housefly strain. Induction with either naphthalene or phenobarbital appears to increase cytochrome P-450I preferentially.
Mol Cell Biochem 1976 Jul 30
PMID:Insect cytochrome P-450. 96 61

When measured in vitro using human placental microsomal preparations, the aromatization of 16alpha-hydroxytestosterone to estriol and androstenedione to estrone and estradiol proceeds at almost identical initial rates. Important differences between 16alpha-hydroxytestosterone and adrostenedione aromatization are evident, however. While substantial findings have implicated cytochrome P-450 in placental aromatization, the aromatizaiton of androstenedione is insensitive to CO although it is competitively inhibited by metyrapone. 16alpha-Hydroxytestosterone aromatization, in contrast, is inhibited 50-60% by CO and is strongly inhibited by metyrapone. 16alpha-hydroxytestosterone aromatization is strongly inhibited in a competitive manner by androstenedione, while 16alpha-hydroxytestosterone has essentially no effect on androstenedione aromatization, althogh at very high 16alpha-hydroxytestosterone concentrations (65 muM) and subsaturating androstenedione concentrations, 16alpha-hydroxytestosterone appears to noncomptitively inhibit androstenedione aromatization. The apparent Km for the aromatization of androstenedione is 95 nM and for 16alpha-hydroxytestosterone, 7 muM. Both androstenedione and 16alpha-hydroxytestosterone cause type I spectral perturbations associated with binding to cytochrome P-450 when added to placental microsomes; however, the deltaA390-420 is twice as great in response to saturating amounts of androstenedione than in response to 16alpha-hydroxytestosterone. If androstenedione is added to 16alpha-hydroxytestosterone, the same spectral change as that caused by androstenedione alone is expressed. The apparent spectral dissociation constant for androstenedione is 93 nM while for 16alpha-hydroxytestosterone it is 11muM; both essentially the same as the comparable apparent Kms for aromatization. The evidence suggests the presence of two aromatase P-450's in human placenta.
Mol Cell Endocrinol 1976 Dec
PMID:Cytochrome P-450 and the aromatization of 16alpha-hydroxytestosterone and androstenedione by human placental microsomes. 100 10

Rat liver mitochondria were fractionated on the basis of their sedimentation coefficients in the gradient of ficoll. The fractions ("heavy", "middle" and "light" mitochondria) were heterogeneous with regard to the content of protein, DNA, cytochrome a + a3 and respiratory activity. Heterogeneity of mitochondria did not result from the damage or microsomal and lysosomal contamination. The biosynthesis of DNA, RNA and proteins in the different fractions of mitochondria was studied. In vivo incorporation of radioactive precursor into RNA was highest in the fractions of "middle" mitochondria, whereas in vitro the "heavy" mitochondria showed maximum activity in the synthesis of RNA. In vitro DNA synthes was maximum in the fractions of "heavy" mitochondria, protein synthesis in "heavy" and "light" mitochondria. Activity of the synthesis of RNA, DNA and proteins in vitro depends on the content of DNA and cytochrome a + a3 in the different fractions of mitochondria. It is supposed that heterogeneity of mitochondria may be connected with their biogenesis.
Mol Biol (Mosk)
PMID:[Biochemical heterogeneity of mitochondria]. 105 68

1. The metabolic role of arterial angiotensin I-forming enzyme (i.e. renin activity) was studied in total homogenates and in subcellular fractions of the aorta of normotensive and hypertensive rats. 2. Angiotensin I-forming enzyme was measured in (a) uninephrectomized rats rendered hypertensive with D-aldosterone and sodium chloride (10 g/l drinking solution, (b) rats treated in the same manner but with the addition of spironolactone, and (c) control rats. 3. Hypertension developed in aldosterone-treated rats within 3-6 weeks and was associated with decreased plasma and renal renin values. Total aortic renin activity was up to sixfold higher in the hypertensive animals than in control animals and there was an increased ratio of supernatant to microsomal renin activity in the aorta. 4. In spironolactone-treated rats blood pressure and total aortic renin concentrations were comparable with those in the control rats. 5. The results support the hypothesis that renin generated at local vascular sites, which is independent of circulating renin levels, contributes to regulation of blood pressure.
Clin Sci Mol Med Suppl 1976 Dec
PMID:Effects of aldosterone and spironolactone on arterial renin in rats. 107 85

1. Long-chain acid: CoA ligase (AMP-forming) (trivial name acyl-CoA synthetase; EC 6.2.1.3) is located at the membranes of the endoplasmic reticulum and the outer membrane of the mitochondria. The latter membrane has by far the highest specific activity. 2. GTP-dependent synthesis of acyl-CoA has a very low activity in liver mitochondria (about 5% of the activity measured with ATP). CTP, ITP, UTP and GTP may all provide energy for fatty acid activation in sonicated mitochondria by formation of ATP from endogenous ADP and AMP. 3. In rat liver palmitoyl-CoA: L-carnitine O-palmitoyltransferase (trivial name carnitine palmitoyltransferase; EC 2.3.1.21) is located at the microsomal membranes and in the inner membrane of the mitochondria. Its activity is increased, in both membranes, during fasting and in thyroxine-treated rats. The extramitochondrial carnitine palmitoyltransferase may capture part of the acyl CoA formed at the endoplasmic reticulum as acyl-carnitine, especially during fasting and other metabolic conditions of high fatty acid turnover. This transport form of activated fatty acid can penetrate the inner mitochondrial membrane (the acyl-CoA barrier) where it can be reconverted to acyl-CoA, providing the substrate for beta-oxidation in the inner membrane-matrix compartment. The small part of the mitochondrial carnitine palmitoyltransferase, described to be present at the external surface of the mitochondrial inner membrane, may have the same function in the transport of acyl-CoA formed at the mitochondrial outer membrane. 4. Isolated rat liver mitochondria can oxidize high concentrations of palmitate or oleate in the absence of carnitine. In this case the fatty acids are activated in the inner membrane-matrix compartment of the mitochondria, probably by a medium-chain acyl-CoA synthetase with wide substrate specificity. Because this enzyme is less active in heart and absent in skeletal muscle, these tissues oxidize long-chain fatty acids in an obligatory carnitine-dependent fashion. Also the liver oxidizes long-chain fatty acids in a carnitine-dependent way if lower fatty acid concentrations are used. In this tissue carnitine stimulates specifically the partial oxidation of fatty acids to beta-hydroxybutyrate and acetoacetate. 5. The activities of acyl-CoA: sn-glycerol-3-phosphate O-acyltransferase (trivial name glycerophosphate acyltransferase; EC 2.3.1.15) and carnitine palmitoyltransferase change in opposite directions during fasting. These activity changes, together with the measured kinetic properties of the enzymes in mitochondria and microsomes, allow a switch (relatively) from lipid synthesis to ketogenesis during fasting. This switch may occur at the level of long-chain acyl-CoA both in the endoplasmic reticulum and in the mitochondria.
Mol Cell Biochem 1975 Apr 30
PMID:Aspects of long-chain acyl-COA metabolism. 113 97


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