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.

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.

THE ENZYMATIC REDUCTION OF TETRAZOLIUM SALTS BY AMINES

1956 ◽  
Vol 34 (1) ◽  
pp. 1095-1106 ◽  
Author(s):  
J. R. Lagnado ◽  
T. L. Sourkes
Keyword(s):  
Rat Brain ◽  
Kinetic Data ◽  
Amine Oxidase ◽  
Enzyme System ◽  
Pig Liver ◽  
Heat Stable ◽  
Rat Brain And Liver ◽  
Enzymatic Reduction ◽  
Reducing Activity ◽  
Cofactor Activity

An enzyme system effecting the dehydrogenation of amines has been detected in rat brain and liver suspensions by the use of tetrazolium dyes as terminal electron acceptors. Kinetic data on this system are presented and the evidence for requirement of a cofactor is described. Thus, after washing or dialysis, rat brain suspensions have a considerably lowered tetrazolium reducing activity, which can be restored by addition of boiled extracts of rat liver, rat brain, pig liver, or baker's yeast. The heat-stable cofactor in pig liver and rat brain which is necessary for the activity of the tetrazolium reducing system is dialyzable. Pig liver extracts lose their cofactor activity on ashing. The nature of the electron transporting system active in amine dehydrogenation is discussed and the properties of the tetrazolium reducing and the amine oxidase systems are compared.

THE ENZYMATIC REDUCTION OF TETRAZOLIUM SALTS BY AMINES

1956 ◽  
Vol 34 (6) ◽  
pp. 1095-1106 ◽  
Author(s):  
J. R. Lagnado ◽  
T. L. Sourkes
Keyword(s):  
Rat Brain ◽  
Kinetic Data ◽  
Amine Oxidase ◽  
Enzyme System ◽  
Pig Liver ◽  
Heat Stable ◽  
Rat Brain And Liver ◽  
Enzymatic Reduction ◽  
Reducing Activity ◽  
Cofactor Activity

An enzyme system effecting the dehydrogenation of amines has been detected in rat brain and liver suspensions by the use of tetrazolium dyes as terminal electron acceptors. Kinetic data on this system are presented and the evidence for requirement of a cofactor is described. Thus, after washing or dialysis, rat brain suspensions have a considerably lowered tetrazolium reducing activity, which can be restored by addition of boiled extracts of rat liver, rat brain, pig liver, or baker's yeast. The heat-stable cofactor in pig liver and rat brain which is necessary for the activity of the tetrazolium reducing system is dialyzable. Pig liver extracts lose their cofactor activity on ashing. The nature of the electron transporting system active in amine dehydrogenation is discussed and the properties of the tetrazolium reducing and the amine oxidase systems are compared.

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.

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.

Metallothionein synthesis and localization in relation to metal storage in rat liver during gestation

1985 ◽  
Vol 63 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Douglas M. Templeton ◽  
Diponkar Banerjee ◽  
M. George Cherian
Keyword(s):  
Rat Liver ◽  
Metal Binding ◽  
Protein Composition ◽  
Progressive Increase ◽  
Immunohistochemical Localization ◽  
Late Gestation ◽  
Adult Rat ◽  
Fetal Rat ◽  
Fetal Rat Liver

The metallothionein (MT) content of fetal rat liver was measured daily during the final week of gestation, by both cadmium saturation and polarographic methods. MT levels rise sharply at day 18 of gestation and continue to increase into the neonatal period. In late gestation, MT serves to bind Cu and Zn from the preexisting hepatic pools of these metals, as well as to accumulate additional amounts of both metals The fetal MT is similar to the adult rat protein both in terms of its protein composition and metal-binding properties. Perinatally the Zn/MT ratio remains constant for several days suggesting a carefully regulated process. At birth, most of the hepatic Zn and a significant amount of hepatic Cu are bound to MT. Immunohistochemical localization of MT shows a progressive increase in cytoplasmic MT with the appearance of nuclear MT by day 20 of gestation in fetal rat liver. The results are discussed in terms of a model for regulation of MT synthesis and for the metal storage role of MT in perinatal development.

scholarly journals Studies on the enzymic degradation of L-serine O-sulphate by a rat liver preparation

1967 ◽  
Vol 105 (2) ◽  
pp. 467-472 ◽  
Author(s):  
J H Thomas ◽  
N. Tudball
Keyword(s):  
Rat Liver ◽  
Enzyme Preparation ◽  
Enzyme System ◽  
Metal Salts ◽  
Optimum Conditions ◽  
Enzyme Action ◽  
Inorganic Sulphate ◽  
Serine Dehydratase ◽  
Liver Preparation

1. The enzyme system of rat liver responsible for the degradation of l-serine O-sulphate was purified 300-fold and the optimum conditions for the activity were determined. 2. Inorganic sulphate, pyruvate and ammonia were found to be the products of enzyme action on lserine O-sulphate, being formed in equivalent amounts under all conditions examined. No free l-serine was detected as a product of enzyme action. 3. The enzyme preparation was free from other serine-metabolizing systems such as O-phospho-l-serine phosphatase and l-serine dehydratase. 4. The enzyme has a very narrow substrate specificity and is inactive towards a wide variety of related sulphate esters and amino acids. 5. Pyridoxal 5′-phosphate is capable of catalysing the non-enzymic breakdown of l-serine O-sulphate in the presence of metal salts to yield inorganic sulphate, pyruvate and ammonia as products. 6. The possible role of pyridoxal 5′-phosphate as a coenzyme in the enzymic degradation of l-serine O-sulphate is discussed.

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