Search results for "Microsome"
showing 10 items of 262 documents
Sequence similarity of mammalian epoxide hydrolases to the bacterial haloalkane dehalogenase and other related proteins Implication for the potential…
1994
Direct comparison of the amino acid sequences of microsomal and soluble epoxide hydrolase superficially indicates that these enzymes are unrelated. Both proteins, however, share significant sequence similarity to a bacterial haloalkane dehalogenase that has earlier been shown to belong to the alpha/beta hydrolase fold family of enzymes. The catalytic mechanism for the dehalogenase has been elucidated in detail [Verschueren et al. (1993) Nature 363, 693-698] and proceeds via an ester intermediate where the substrate is covalently bound to the enzyme. From these observations we conclude (i) that microsomal and soluble epoxide hydrolase are distantly related enzymes that have evolved from a co…
Identification and Characterization of a Novel Epoxide Hydrolase From Mouse Liver Microsomes
1982
A new microsomal epoxide hydrolase (mEH2) has been identified and characterized. This enzyme has properties which distinguish it from previously described cytosolic (cEH) or membrane-bound (mEH1) epoxide hydrolases. The enzyme is an integral microsomal protein which is not dissociated from the membrane by repeated washing, high ionic strength salt, or chaotropic agent solutions, or by sonication. It is very different from the normally described microsomal epoxide hydrolase (mEH1) as shown by its different substrate specificity and kinetic properties and by immunological criteria. In contrast to the hitherto described microsomal epoxide hydrolase, mEH1, the new enzyme effectively catalyzes t…
Rat Cytosolic Epoxide Hydrolase
1986
Rat liver microsomal and cytosolic epoxide hydrolase may be distinguished through differences in substrate specificity: styrene 7,8-oxide is preferentially hydrolyzed by the microsomal form, while trans-stilbene oxide is the prefered substrate for cytosolic epoxide hydrolase. Large interindividual differences in the specific activity of SpragueDawley (outbred strain) liver cytosolic epoxide hydrolase were observed, varying from 2 to 77 pmol/min x mg protein. Interindividual variations were much lower for microsomal epoxide hydrolase. The specific activity of Fischer F-344 (inbred strain) liver cytosolic epoxide hydrolase varied only by a factor of 2. The specific activity of cytosolic epoxi…
Dietary fish protein lowers blood pressure and alters tissue polyunsaturated fatty acid composition in spontaneously hypertensive rats.
2003
Abstract Objectives To investigate the effect of two types of dietary protein on blood pressure, liver fatty acid desaturation and composition, and urine 6-keto-prostaglandin-F (PGF1α) level, the metabolite of prostacyclin. Methods 5-wk-old spontaneously hypertensive rats were fed 20% casein or purified fish protein. The fat source was 5% ISIO oil, which contains 47.9% (ω-6) and 1.7% (ω-3) total polyunsaturated fatty acids. After 2 mo on the diet, systolic blood pressure was reduced with fish protein compared with casein (189.8 ± 10.5 versus 220.7 ± 8.7). Results Excretion of 6-keto-PGF1α in urine was negatively correlated with blood pressure. Liver cholesterol and phospholipid concentratio…
Delta 5-desaturation of dihomogammalinolenic acid (20:3(n-6)) into arachidonic acid (20:4(n-6)) by rat liver microsomes and incorporation of fatty ac…
1991
Abstract Liver microsomes of rats fed an essential fatty acid (EFA)-deficient diet or a commercial balanced diet were used to study the effect of incubation time on the Δ 5 -desaturation of [ 14 C] dihomogammalinolenic acid (20:3( n −6)) into arachidonic acid (20:4( n −6)) and incorporation of the two acids into microsomal phospholipids. The EFA-deficient diet highly increased the desaturation rate of 20:3( n −6). Incorporation of the formed 20:4( n −6) into microsomal phospholipids was also increased but at saturating concentration of substrate only. At early times of incubation, the precursor 20:3( n −6) was rapidly incorporated into phospholipids. Formation and incorporation of 20:4( n −…
Effect of simvastatin on desaturase activities in liver from lean and obese zucker rats
1993
The effect of simvastatin, a hypocholesterolemic drug, on the biosynthesis of arachidonic acid was studied in obese and lean Zucker rats. After administration of 2 mg/kg body weight/d for 13 d, delta 6 and delta 5 desaturase activities were measured in liver microsomes at two substrate concentrations. In untreated rats, the delta 6 desaturation rate was similar in the obese and lean rats when measured at saturating substrate levels, whereas delta 5 desaturation was lower in the obese animals. Treatment with simvastatin did not change delta 6 desaturation in either phenotype but increased delta 5 desaturation in obese rats to reach the unchanged rate observed in lean animals. The changes wer…
Age-related changes in delta 6 and delta 5 desaturase activities in rat liver microsomes.
1993
Age-related changes in Δ6 desaturation of [1-14C]α-linolenic acid and [1-14C]linoleic acid and in Δ5 desaturation of [2-14C]dihomo-γ-linolenic acid were studied in liver microsomes from Wistar male rats at various ages ranging from 1.5 to 24 mon. Desaturase activities were expressed both as specific activity of liver microsomes and as the capacity of whole liver to desaturate by taking into account the total amount of liver microsomal protein. Δ6 Desaturation of α-linolenic acid increased from 1.5 to 3 mon and then decreased linearly up to 24 mon to reach the same desaturation capacity of liver measured at 1.5 mon. The capacity of liver to desaturate linoleic acid increased up to 6 mon and …
Effect of Salt-Loading and Spontaneous Hypertension on in Vitro Metabolism of [1-14C]Linoleic and [2-14C]Dihomo-γ-linolenic Acids
1993
The present study compared the effect of spontaneous hypertension and salt-loading on in vitro metabolism of 18:2n-6 (linoleic acid) and 20:3n-6 (dihomo-gamma-linolenic acid). Ten weanling spontaneously hypertensive rats (SHR) and 10 normotensive Wistar-Kyoto rats (WKY) maintained on a rodent lab chow were given tap water with (n = 5) or without (n = 5) addition of 1% NaCl for 4 weeks. Thereafter, animals were killed and liver microsomes were prepared. Aliquots of microsomes suspended in the phosphate-sucrose buffer containing MgCl2, ATP, CoA, and NADPH were incubated with 0.3 microCi of [1-14C]-18:2n-6 or [2-14C]-20:3n-6 at 37 degrees C for 15 min. The activity of delta 6- and delta 5-desa…
Liver microsomal membrane fluidity and microsomal desaturase activities in adult spontaneously hypertensive rats.
1997
OBJECTIVE The purpose of the present study was to investigate liver microsomal membrane fluidity simultaneously with membrane fatty acid composition and desaturase activities in spontaneously hypertensive rats (SHR). DESIGN AND METHODS The membrane fluidity was determined, after electron spin resonance (ESR) measurement, in SHR compared with normotensive Wistar-Kyoto (WKY) rats, by calculating the order parameter S from ESR spectra of 5-nitroxide stearate and 10-nitroxide stearate, used as spin-labelled fatty acids. Desaturase activities were measured by incubating SHR and WKY rat liver microsomes with [14C]-radiolabeled fatty acids as substrates for desaturation reactions. The fatty acid c…
Effect of sodium loading (3% NaCl) on arachidonic acid biosynthesis in rat liver microsomes
1992
Sodium loading increases arachidonic acid (AA) metabolism by way of the prostaglandins(PGs) from series 2. Its effect on AA biosynthesis remains unknown. The purpose of the present study was to investigate the influence of sodium loading on the fatty acid composition of liver and liver microsomes, and the liver microsomal delta-6 and delta-5 desaturations of linoleic acid (LA) into AA. We found a decrease of LA and dihomo-gamma-linolenic acid (DGLA) levels in liver total lipids of Wistar rats receiving hypernatriuretic drinking water (NaCl 3%) for 60 days. At the same time AA increased. DGLA decreased and AA increased in liver microsomal total lipids. 1(14) C-LA delta-6 desaturase and 2(14)…