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.

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 Enzymic sulphation of p-nitrophenol and steroids by larval gut tissues of the southern armyworm (Prodenia eridania Cramer)

1972 ◽  
Vol 130 (2) ◽  
pp. 487-493 ◽  
Author(s):  
R. S. H. Yang ◽  
C. F. Wilkinson
Keyword(s):  
Enzyme Preparation ◽  
Soluble Fraction ◽  
Enzyme System ◽  
Endocrine Control ◽  
Southern Armyworm ◽  
Inorganic Sulphate

1. An enzyme system that catalyses the sulphation of p-nitrophenol, cholesterol, α-ecdysone, β-sitosterol, dehydroepiandrosterone, oestrone and four other steroids of plant and insect origin was obtained from the soluble fraction of southern-armyworm gut tissues. 2. The enzyme system required ATP and inorganic sulphate, and activity was slightly enhanced in the presence of GSH. 3. The properties of this enzyme system with respect to pH, temperature, substrate and protein concentrations and various cofactors and reagents were studied. At −23°C the enzyme preparation could be stored for 2 weeks without drastic loss of activity. At the end of storage for 1 month the loss of activity was approx. 21%. 4. The possible involvement of this enzyme system in insect endocrine control is discussed.

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.

Taurocholate induces directional excretion of bilirubin into bile in perfused rat liver

1996 ◽  
Vol 270 (6) ◽  
pp. G1028-G1032 ◽  
Author(s):  
T. Yamaguchi ◽  
Y. Wakabayashi ◽  
M. Tanaka ◽  
T. Sano ◽  
H. Ishikawa ◽  
...  
Keyword(s):  
Rat Liver ◽  
Total Bilirubin ◽  
Liver Parenchyma ◽  
Isolated Perfused Rat Liver ◽  
Perfused Liver ◽  
Perfused Rat Liver ◽  
Liver Preparation ◽  
Directional Transport ◽  
Conjugated Bile Acids

The role of taurocholate, one of the major conjugated bile acids present in portal blood, in excretion of bilirubin from liver parenchyma to biliary and vascular compartments was studied in isolated perfused rat liver. Contents of bilirubin and carbon monoxide (CO) in the bile or venous effluents were determined by enzyme-linked immunosorbent microassay with the use of antibilirubin monoclonal antibody 24G7 and myoglobin-assisted spectrophotometry, respectively. In the presence of taurocholate, bilirubin excreted into the biliary compartment constituted greater than 90% of the total bilirubin excreted from the liver (0.26 nmol.min-1.g liver-1), corresponding to 60% of the outflow of CO into the venous effluents. In its absence, however, the total amount of bilirubin excreted into extrahepatic compartments was reduced to 27% of CO flux, and more than 90% of the excreted bilirubin was in the venous effluent. Thus a choleretic bile acid such as taurocholate is necessary for directional transport of bilirubin into bile in the perfused liver preparation.

scholarly journals POPULATION GENETICS OF DROSOPHILA AMYLASE. IV. SELECTION IN LABORATORY POPULATIONS MAINTAINED ON DIFFERENT CARBOHYDRATES

Genetics ◽  
1983 ◽  
Vol 103 (4) ◽  
pp. 675-689
Author(s):  
Jeffrey R Powell ◽  
Marko Andjelković
Keyword(s):  
Structural Gene ◽  
Amylase Activity ◽  
Enzyme System ◽  
Specific Expression ◽  
Carbohydrate Source ◽  
Laboratory Populations ◽  
Consistent Change ◽  
Regulation Changes ◽  
Starch Medium

ABSTRACT Two polymorphic systems impinging on α-amylase in Drosophila pseudoobscura have been studied in laboratory populations maintained on medium in which the only carbohydrate source was starch (the substrate of amylase) and replicas maintained on medium in which the only carbohydrate source was maltose (the product of amylase). The two polymorphic systems were alleles at the structural gene (Amy) coding for the enzyme (allozymes) and variation in the tissue-specific expression along the adult midgut controlled by several genes. In the seven populations on maltose medium little consistent change was noted in either system. In the seven populations on starch medium, both polymorphisms exhibited selective changes. A midgut pattern of very limited expression of amylase rose in frequency in all starch populations, as did the frequency of the "fast" (1.00) Amy allele. The overall specific amylase activity did not differ between starch-adapted and maltose-adapted flies.—The results, along with previous studies, indicate that when a gene-enzyme system is specifically stressed in laboratory populations, allozymes often exhibit selective differences. Such results make the selectionist hypothesis at least tenable. Furthermore, the fact that both types of polymorphisms responded to selection indicates the role of structural gene vs. gene regulation changes in adaptive evolution is not an either/or question but one of relative roles and interactions.

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