BIOGENESE VON ÖSTRIOL-16α-MONOGLUCURONID UND ÖSTRIOL-17β-MONOGLUCURONID

1966 ◽  
Vol 52 (1) ◽  
pp. 43-53 ◽  
Author(s):  
K. Dahm ◽  
H. Breuer
Keyword(s):  
Rat Liver ◽  
Steric Hindrance ◽  
Microsomal Fraction ◽  
Enzyme System ◽  
The Other ◽  
Human Intestine ◽  
Main Metabolite ◽  
Enzyme Preparations ◽  
Glucuronyl Transferase ◽  
Enzymatic Reduction

ABSTRACT The biogenesis of oestriol 16α-monoglucuronide and oestriol 17β-monoglucuronide has been studied using different enzyme preparations of human intestine, placenta and liver as well as of rat liver. After incubation of oestriol with the microsomal fraction of human intestine or rat liver, oestriol 16α-monoglucuronide was found as main metabolite, whereas oestriol 17β-monoglucuronide was formed in smaller amounts. When the 100 000 × g supernatant of human intestine was precipitated with ammonium sulphate (30–60% saturation), a glucuronyl transferase was obtained which catalysed the formation of oestriol 17β-monoglucuronide only. No oestriol 16α-monoglucuronide was found when 16α-hydroxyoestrone 16α-monoglucuronide was incubated with either the cytoplasmic 17β-hydroxysteroid:NAD(P)-oxidoreductase of human intestine and rat liver or with a 37-fold purified human placental 17β-hydroxysteroid:NAD-oxidoreductase. On the other hand, no oestriol 17β-monoglucuronide was formed when 17β-oestradiol 17β-monoglucuronide was subjected to the action of the microsomal 16α-hydroxylase of rat liver. These results may be explained by steric hindrance of the enzyme system involved. On the basis of the present findings it can be concluded that oestriol 16α-monoglucuronide arises exclusively by direct glucuronidation of oestriol, and not by enzymatic reduction of 16α-hydroxyoestrone 16α-monoglucuronide. Similarly, oestriol 17β-monoglucuronide is most probably formed only by direct glucuronidation of oestriol, and not by 16α-hydroxylation of 17β-oestradiol 17β-monoglucuronide.

BIOGENESE VON ÖSTRIOL-3-MONOGLUCURONID

1967 ◽  
Vol 56 (3) ◽  
pp. 403-412 ◽  
Author(s):  
K. Dahm ◽  
Monika Lindlau ◽  
H. Breuer
Keyword(s):  
Rat Liver ◽  
Steric Hindrance ◽  
Microsomal Fraction ◽  
Enzyme System ◽  
The Other ◽  
Human Intestine ◽  
Enzyme Preparations ◽  
Other Hand ◽  
Enzymatic Reduction

ABSTRACT The biogenesis of oestriol 3-monoglucuronide has been studied using different enzyme preparations of human intestine and placenta as well as of rat liver. After incubation of oestriol with the microsomal fraction of human intestine, oestriol 3-monoglucuronide was found in addition to oestriol 16α-monoglucuronide and oestriol 17β-monoglucuronide. No oestriol 3-monoglucuronide was found when 16α-hydroxyoestrone 3-monoglucuronide, prepared biosynthetically, was incubated with a 24-fold purified human placental 17β-hydroxysteroid:NAD-oxidoreductase. On the other hand, no oestriol 3-monoglucuronide was formed when 17β-oestradiol 3-monoglucuronide was subjected to the action of the microsomal 16α-hydroxylase of rat liver. These results may be explained by steric hindrance of the enzyme system involved. On the basis of the present findings it can be concluded that oestriol 3-monoglucuronide arises exclusively by direct glucuronidation of oestriol, and not by enzymatic reduction of 16α-hydroxyoestrone 3-monoglucuronide or by 16α-hydroxylation of 17β-oestradiol 3-monoglucuronide.

Conversion of Flavanone to Flavone, Dihydroflavonol and Flavonol with an Enzyme System from Cell Cultures of Parsley

1981 ◽  
Vol 36 (9-10) ◽  
pp. 742-750 ◽  
Author(s):  
L. Britsch ◽  
W. Heller ◽  
H. Grisebach
Keyword(s):  
Microsomal Fraction ◽  
Specific Activity ◽  
Enzyme System ◽  
High Specific Activity ◽  
Cell Suspension Cultures ◽  
Soluble Enzyme ◽  
Enzyme Preparations ◽  
Malonyl Coa ◽  
In Vitro Biosynthesis

Abstract Soluble enzyme preparations from irradiated cell suspension cultures of parsley (Petroselinum hortense Hoffm.) catalyse the conversion of flavanone to flavone, dihydroflavonol and flavonol. These reactions require 2-oxoglutarate, Fe2+ and ascorbate as cofactors. In the presence of these cofactors conversion of dihydroflavonol to flavonol was also observed. With this system in vitro biosynthesis of radioactive flavone, dihydroflavonol and flavonol from [2-14C]malonyl-CoA and 4-coumaroyl-CoA in good yield and with high specific activity is possible.We postulate that synthesis of flavone and flavonol from flavanone proceeds via 2-hydroxy-and 2,3-dihydroxyflavanone, respectively, with subsequent dehydration.The microsomal fraction of the parsley cells contains an NADPH-dependent flavanone 3'-hydroxylase.

FURTHER OBSERVATIONS ON THE ENZYMATIC REDUCTION OF TETRAZOLIUM SALTS BY MONOAMINES

1958 ◽  
Vol 36 (6) ◽  
pp. 587-594 ◽  
Author(s):  
J. R. Lagnado ◽  
T. L. Sourkes
Keyword(s):  
Rat Liver ◽  
Metal Binding ◽  
Enzyme System ◽  
Enzymatic Reaction ◽  
Free Base ◽  
Tetrazolium Salts ◽  
Enzymatic Reduction ◽  
Tissue Homogenates ◽  
Cofactor Activity

Studies on the role of purines as cofactors in the enzymatic reduction of tetrazolium salts by monoamines have led to the following results: (1) With whole rat liver extracts as the source of enzymes, several purines exhibit cofactor activity either as the free base or as the corresponding riboside and ribotide derivatives. (2) In contrast to this, mitochondrial material from rat liver is active only if adenylic acid or one of several ribotidic derivatives containing an adenylyl or similar moiety is used as cofactor. (3) Mitochondrial material utilizes hypoxanthine as cofactor for the amine/tetrazolium system only in combination with the supernatant obtained by centrifugation of tissue homogenates at 20,000 g. The additional factor present in this supernatant portion is heat-labile and nondialyzable. The possibility that this additional factor is an enzyme or enzymes converting the free base to the ribotide is discussed.Inhibition studies have revealed that the amine/tetrazolium enzyme system is sensitive to several metal-binding agents, but no direct evidence for the role of a metal in the enzymatic reaction could be obtained. It was also found that nicotinamide and adenine, neither of which exhibits cofactor activity, are potent inhibitors of the enzyme system studied.

scholarly journals Identity of purified monoacylglycerol lipase, palmitoyl-CoA hydrolase and aspirin-metabolizing carboxylesterase from rat liver microsomal fractions. A comparative study with enzymes purified in different laboratories

1985 ◽  
Vol 232 (2) ◽  
pp. 479-483 ◽  
Author(s):  
R Mentlein ◽  
R K Berge ◽  
E Heymann
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Monoacylglycerol Lipase ◽  
Enzyme Preparations ◽  
Nitrophenyl Phosphate ◽  
Liver Microsomal Fraction ◽  
Coa Hydrolase ◽  
Rat Liver Cytosol

Two purified carboxylesterases that were isolated from a rat liver microsomal fraction in a Norwegian and a German laboratory were compared. The Norwegian enzyme preparation was classified as palmitoyl-CoA hydrolase (EC 3.1.2.2) in many earlier papers, whereas the German preparation was termed monoacylglycerol lipase (EC 3.1.1.23) or esterase pI 6.2/6.4 (non-specific carboxylesterase, EC 3.1.1.1). Antisera against the two purified enzyme preparations were cross-reactive. The two proteins co-migrate in sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Both enzymes exhibit identical inhibition characteristics with Mg2+, Ca2+ and bis-(4-nitrophenyl) phosphate if assayed with the two substrates palmitoyl-CoA and phenyl butyrate. It is concluded that the two esterase preparations are identical. However, immunoprecipitation and inhibition experiments confirm that this microsomal lipase differs from the palmitoyl-CoA hydrolases of rat liver cytosol and mitochondria.

FURTHER OBSERVATIONS ON THE ENZYMATIC REDUCTION OF TETRAZOLIUM SALTS BY MONOAMINES

1958 ◽  
Vol 36 (1) ◽  
pp. 587-594 ◽  
Author(s):  
J. R. Lagnado ◽  
T. L. Sourkes
Keyword(s):  
Rat Liver ◽  
Metal Binding ◽  
Enzyme System ◽  
Enzymatic Reaction ◽  
Free Base ◽  
Tetrazolium Salts ◽  
Enzymatic Reduction ◽  
Tissue Homogenates ◽  
Cofactor Activity

Studies on the role of purines as cofactors in the enzymatic reduction of tetrazolium salts by monoamines have led to the following results: (1) With whole rat liver extracts as the source of enzymes, several purines exhibit cofactor activity either as the free base or as the corresponding riboside and ribotide derivatives. (2) In contrast to this, mitochondrial material from rat liver is active only if adenylic acid or one of several ribotidic derivatives containing an adenylyl or similar moiety is used as cofactor. (3) Mitochondrial material utilizes hypoxanthine as cofactor for the amine/tetrazolium system only in combination with the supernatant obtained by centrifugation of tissue homogenates at 20,000 g. The additional factor present in this supernatant portion is heat-labile and nondialyzable. The possibility that this additional factor is an enzyme or enzymes converting the free base to the ribotide is discussed.Inhibition studies have revealed that the amine/tetrazolium enzyme system is sensitive to several metal-binding agents, but no direct evidence for the role of a metal in the enzymatic reaction could be obtained. It was also found that nicotinamide and adenine, neither of which exhibits cofactor activity, are potent inhibitors of the enzyme system studied.

DEMETHYLIERUNG VON METHOXYÖSTROGENEN IN VITRO UND IN VIVO

1964 ◽  
Vol 46 (3) ◽  
pp. 361-378 ◽  
Author(s):  
H. Breuer ◽  
Marlene Knuppen ◽  
D. Gross ◽  
C. Mittermayer
Keyword(s):  
Intravenous Injection ◽  
Rat Liver ◽  
Intravenous Administration ◽  
Microsomal Fraction ◽  
Enzyme System ◽  
Average Yield ◽  
Experimental Conditions ◽  
Menten Constant

ABSTRACT The microsomal fraction of rat liver contains an enzyme system which, in the presence of NADPH2 and oxygen, demethylates 2-methoxyoestradiol-17β to 2-hydroxyoestradiol-17β. Under similar experimental conditions, 3-methoxyoestradiol-17β is demethylated to oestradiol-17β. The demethylation of 3-methoxyoestradiol-17β shows an optimum at pH 7.4 and is inhibited by β-diethylaminoethyl diphenylpropylacetate; the type of inhibition seems to be noncompetitive. The Michaelis-Menten constant for 3-methoxyoestradiol-17β was found to be 2.0 × 10−4 m. It appears that demethylation of 2- and 3-methoxyoestrogens is catalysed by a non-specific ether-cleaving enzyme system. After intravenous injection of 20 mg of 3-methoxyoestradiol-17β into 3 patients, the excretion of oestradiol-17β, oestrone and oestriol in the urine showed a marked increase. The average yield of the 3 urinary oestrogens derived from 3-methoxyoestradiol-17β was 2.7% of the dose administered. By using corrections for metabolic and method losses, a demethylation rate of 17.5% for 3-methoxyoestradiol-17β was calculated. The concentrations of oestradiol-17β, oestrone and oestriol in bile also increased after intravenous administration of 3-methoxyoestradiol-17β. The maximum concentrations of oestrone and oestradiol-17β were found immediately after injection, whereas the maximum in the oestriol fraction occurred 4 h later. Oestrone was predominantly excreted in the sulphate fraction, but most of the oestriol was found in the glucuronoside fraction. These results suggest that demethylation of methoxyoestrogens takes place in liver. Some of the biochemical and physiological aspects of demethylation are discussed.

Influence of curcumin, capsaicin, and piperine on the rat liver drug-metabolizing enzyme system in vivo and in vitro

2006 ◽  
Vol 84 (12) ◽  
pp. 1259-1265 ◽  
Author(s):  
D. Suresh ◽  
K. Srinivasan
Keyword(s):  
Rat Liver ◽  
Enzyme System ◽  
Transferase Activity ◽  
Glucuronyl Transferase ◽  
Microsomal Cytochrome ◽  
Assay Medium ◽  
Drug Metabolizing Enzyme ◽  
Metabolizing Enzyme ◽  
Aryl Hydroxylase

The effect of dietary supplementation of spice-active principles, curcumin (0.2%), capsaicin (0.015%), and piperine (0.02%) on the activities of the liver drug-metabolizing enzyme system was examined. All the 3 dietary spice principles significantly stimulated the activity of aryl hydroxylase. A synergistic action of dietary curcumin and capsaicin with respect to stimulating the activity of aryl hydroxylase was also evidenced when fed in combination. The activity of N-demethylase essentially remained unaffected by dietary curcumin, capsaicin, or their combination, but was significantly lowered as a result of piperine feeding. Uridine dinucleotide phosphate (UDP)-glucuronyl transferase activity was decreased by dietary piperine and the combination of curcumin and capsaicin. NADPH-cytochrome c reductase activity was significantly decreased by dietary piperine. The levels of hepatic microsomal cytochrome P450 and cytochrome b5 were not influenced by any of the dietary spice-active principles. These spice-active principles were also examined for their possible in vitro influence on the components of the hepatic drug-metabolizing enzyme system in rat liver microsomal preparation. Piperine significantly decreased the activity of liver microsomal aryl hydroxylase activity when included in the assay medium at 1 × 10−6 mol/L, 1 × 10−5 mol/L, and 1 × 10−4 mol/L level. Lowered activity of N-demethylase was observed in presence of capsaicin or piperine at 1 × 10−6 mol/L in the assay medium. Hepatic microsomal glucuronyl transferase activity was significantly decreased in vitro by addition of capsaicin or piperine. Capsaicin and piperine brought about significant decrease in liver microsomal cytochrome P450 when included at 1 × 10−6 mol/L and 1 × 10−5 mol/L, the effect being much higher in the case of piperine. The results suggested that whereas the 3 spice principles have considerable similarity in structure, piperine is exceptional in its influence on the liver drug-metabolizing enzyme system. The study also indicated that a combination of curcumin and capsaicin does not produce any significant additive effect on the liver drug-metabolizing enzyme system.

The Kidney and Fibrinolysis

1970 ◽  
Vol 24 (01/02) ◽  
pp. 026-032 ◽  
Author(s):  
N. A Marsh
Keyword(s):  
Molecular Weight ◽  
Plasminogen Activator ◽  
Enzyme System ◽  
Normal Animal ◽  
Fibrinolytic Enzyme ◽  
The Other ◽  
Exclusion Chromatography ◽  
Normal Urine ◽  
Renal Origin ◽  
Molecular Exclusion Chromatography

SummaryMolecular exclusion chromatography was performed on samples of urine from normal and aminonucleoside nephrotic rats. Normal urine contained 2 peaks of urokinase activity, one having a molecular weight of 22,000 and the other around 200,000. Nephrotic urine contained three peaks of activity with MW’s 126,000, 60,000 and 30,000. Plasma activator determined from euglobulin precipitate had a MW. in excess of 200,000. The results indicate that in the normal animal, plasma plasminogen activator does not escape into the urine in substantial quantities but under the conditions of extreme proteinuria there may be some loss through the kidney. The alteration in urokinase output in nephrotic animals indicates a greatly disordered renal fibrinolytic enzyme system.The findings of this study largely support the hypothesis that plasma plasminogen activator of renal origin and urinary plasminogen activator (urokinase) are different molecular species.

METABOLISM OF 17α-HYDROXYPROGESTERONE-4-14C-17α-CAPROATE BY HOMOGENATES OF RAT LIVER AND HUMAN PLACENTA

1961 ◽  
Vol 36 (4) ◽  
pp. 511-519 ◽  
Author(s):  
Margaret Wiener ◽  
Charles I. Lupa ◽  
E. Jürgen Plotz
Keyword(s):  
Rat Liver ◽  
Human Placenta ◽  
Steric Hindrance ◽  
Placental Tissue ◽  
Caproic Acid ◽  
Major Product ◽  
Side Chain ◽  
Anaerobic Conditions ◽  
Prolonged Action ◽  
Long Acting

ABSTRACT 17α-hydroxyprogesterone-4-14C-17α-caproate (HPC), a long-acting progestational agent, was incubated with homogenates of rat liver and human placenta. The rat liver was found to reduce Ring A of HPC under anaerobic conditions to form allopregnane-3β,17α-diol-20-one-17α-caproate and pregnane-3β,17α-diol-20-one-17α-caproate, the allopregnane isomer being the major product. The caproic acid ester was neither removed nor altered during the incubation. Placental tissue did not attack HPC under conditions where the 20-ketone of progesterone was reduced. It is postulated that this absence of attack on the side chain is due to steric hindrance from the caproate ester, and that this may account for the prolonged action of HPC.

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