scholarly journals Intracellular enzymes of collagen biosynthesis in rat liver as a function of age and in hepatic injury induced by dimethylnitrosamine. Purification of rat prolyl hydroxylase and comparison of changes in prolyl hydroxylase activity with changes in immunoreactive prolyl hydroxylase

1976 ◽  
Vol 158 (2) ◽  
pp. 369-376 ◽  
Author(s):  
J Risteli ◽  
L Tuderman ◽  
K I Kivirikko
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Hepatic Injury ◽  
Specific Activity ◽  
Prolyl Hydroxylase ◽  
Newborn Rats ◽  
Hydroxylase Activity ◽  
Immunoreactive Protein ◽  
Molecular Weights ◽  
Polypeptide Chains

Prolyl hydroxylase was purified from newborn rats by affinity chromatography using poly(L-proline), and antiserum to the enzyme was prepared in rabbits. The rat prolyl hydroxylase was similar to the chick and human enzymes with respect to specific activity, molecular weight and molecular weights of the polypeptide chains. The activity of prolyl hydroxylase and the content of immunoreactive enzyme were measured in rat liver as a function of age in experimental hepatic injury. Active prolyl hydroxylase comprised about 13.2% of the total immunoreactive protein in the liver of newborn rats and the value decreased to about 3.6% at the age of 420 days. This decrease was due to a decrease in the enzyme activity, whereas only minor changes were found in the content of the immunoreactive protein. In hepatic injury, a significant increase was found in the ratio of active enzyme to total immunoreactive protein, owing to an increase in the enzyme activity. The data indicate that prolyl hydroxylase activity in rat liver is controlled in part by a mechanism which does not involve changes in the content of the total immunoreactive protein.

scholarly journals Intracellular enzymes of collagen biosynthesis in rat liver as a function of age and in hepatic injury induced by dimethylnitrosamine. Changes in prolyl hydroxylase, lysyl hydroxylase, collagen galactosyltransferase and collagen glucosyltransferase activities

1976 ◽  
Vol 158 (2) ◽  
pp. 361-367 ◽  
Author(s):  
J Risteli ◽  
K I Kivirikko
Keyword(s):  
Rat Liver ◽  
Enzyme Activities ◽  
Hepatic Injury ◽  
Prolyl Hydroxylase ◽  
Collagen Biosynthesis ◽  
Hydroxylase Activity ◽  
Post Translational Modifications ◽  
Lysyl Hydroxylase ◽  
Intracellular Enzymes ◽  
The Relationship

The relationship between the changes in the four enzyme activities catalysing intracellular post-translational modifications in collagen biosynthesis were studied in rat liver as a function of age and in experimental hepatic injury induced by the administration of dimethylnitrosamine. During aging, relatively large changes were found in prolyl hydroxylase and lysyl hydroxylase activities, whereas only minor changes took place in collagen galactosyltransferase and collagen glucosyltransferase activities. In hepatic injury, the two hydroxylase activities increased earlier and to a larger extent than did the two glycosyltransferase activities, and the largest was found in lysyl hydroxylase activity. The data support previous suggestions that changes in the rate of collagen biosynthesis in the liver cannot be explained simply by a change in the number of collagen-producing cells, but regulation of the enzyme activities existed, so that the two hydroxylase activities altered considerably more than did the two collagen glycosyltransferase activities.

scholarly journals Reconstitution of purified Wistar rat liver bilirubin UDP-glucuronyltransferase into Gunn-rat liver microsomes

1982 ◽  
Vol 201 (3) ◽  
pp. 653-656 ◽  
Author(s):  
B Burchell
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Specific Activity ◽  
Liver Microsomes ◽  
Wistar Rat ◽  
Transferase Activity ◽  
Rat Liver Microsomes ◽  
Phosphatidylcholine Liposomes ◽  
Gunn Rat ◽  
Rigid Environment

1. Reconstitution of purified bilirubin UDP-glucuronyltransferase from Wistar-rat liver into Gunn-rat liver microsomes provides a better environment than phosphatidylcholine liposomes, such that the final specific activity of the Wistar-rat liver enzyme was increased up to 85 units/mg of protein. 2. Gunn- and Wistar-rat liver microsomes were equally effective for reconstitution of the purified enzyme. 3. The transferase activity does not appear to be fully expressed in the more rigid environment of foetal Wistar-rat liver microsomes. 4. These reconstitution experiments reveal a final specific activity for the purified bilirubin UDP-glucuronyltransferase consistent with the capacity of the whole rat liver to glucuronidate bilirubin and indicate that the absence of this enzyme activity in Gunn-rat liver microsomes is not due to an abnormal microenvironment.

A new bilirubin-degrading enzyme from orange peels

1988 ◽  
Vol 66 (11) ◽  
pp. 1248-1252 ◽  
Author(s):  
Tai-Wing Wu ◽  
Grace S. Li
Keyword(s):  
Enzyme Activity ◽  
Absorption Spectrum ◽  
Cholic Acid ◽  
Rat Liver ◽  
Specific Activity ◽  
Unconjugated Bilirubin ◽  
Proteinase K ◽  
Bilirubin Oxidase ◽  
Orange Peels ◽  
Poorly Soluble

A novel enzyme activity that catalyzes the degradation of unconjugated bilirubin (Bu) has been demonstrated in extracts of the peels of edible oranges. Unlike the few known bilirubin-oxidizing enzymes, the orange enzyme does not produce biliverdin as a product, does not seem to require oxygen, and has a unique absorption spectrum of its products. Even at the crude stage, the enzyme has a specific activity that is 10 and 20 times higher, respectively, than those reported for the crude or partially purified Bu-degrading enzymes from mushrooms and rat liver. The enzyme has apH optimum near 7.5 and a Km value of 50–100 μM for Bu. The enzyme is remarkably stable, retaining over 50% activity after prolonged digestion with proteinase K or heating at 100 °C. Similar treatments inactivated the bilirubin oxidase from Myrothecium verrucaria MT-1. The enzyme is poorly soluble in water but can be partially solubilized with cholic acid, with a doubling in specific activity.

scholarly journals The reaction of a histidine residue in glutamate dehydrogenase with diethyl pyrocarbonate

1973 ◽  
Vol 133 (1) ◽  
pp. 183-187 ◽  
Author(s):  
Robert B. Wallis ◽  
J. John Holbrook
Keyword(s):  
Molecular Weight ◽  
Enzyme Activity ◽  
Steady State ◽  
Glutamate Dehydrogenase ◽  
Specific Activity ◽  
Histidine Residue ◽  
Apparent Change ◽  
Diethyl Pyrocarbonate ◽  
Polypeptide Chains ◽  
Rate Limiting

1. One mol of diethyl pyrocarbonate will react with one mol of glutamate dehydrogenase polypeptide chains to form one mol of N1-carbethoxyhistidine. Reaction is prevented by NADH. 2. The 1:1 complex has an increased specific activity (1.4–2.0-fold). 3. The reason for the activation is discussed. The results are not consistent with NADH dissociation from the enzyme–glutamate–NADH complex being rate-limiting in the steady state measured. 4. The effects of modification on the properties of the enzyme were investigated. The effects of GTP and NAD+ on the enzyme activity are unaltered by activation. NADH binding is unaltered and there is no apparent change in the molecular weight. However, the activated enzyme can still be further activated by ADP. Ks for ADP is decreased fivefold.

scholarly journals The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

1970 ◽  
Vol 117 (2) ◽  
pp. 319-324 ◽  
Author(s):  
G. J. Mulder
Keyword(s):  
Enzyme Activity ◽  
Density Gradient ◽  
Rat Liver ◽  
Microsomal Fraction ◽  
Specific Activity ◽  
Sucrose Density Gradient ◽  
Male Rats ◽  
Uridine Diphosphate ◽  
Triton X

1. The detergent Triton X-100 activates UDP glucuronyltransferase from rat liver in vitro six- to seven-fold with p-nitrophenol as substrate. The enzyme activity when measured in the presence of Triton X-100 is increased significantly by pretreatment of male rats with phenobarbital for 4 days (90mg/kg each day intraperitoneally). If no Triton X-100 is applied in vitro such an increase could not be shown. In all further experiments the enzyme activity was measured after activation by Triton X-100. 2. The Km of the enzyme for the substrate p-nitrophenol does not change on phenobarbital pretreatment. 3. When the microsomal fraction from the liver of untreated rats is subfractionated on a sucrose density gradient, 47% of the enzyme activity is recovered in the rough-surfaced microsomal fraction, which also has a higher specific activity than the smooth-surfaced fraction. 4. Of the increase in activity after the phenobarbital pretreatment 50% occurs in the smooth-surfaced fraction, 19% in the rough-surfaced fraction and 31% in the fraction located between the smooth- and rough-surfaced microsomal fractions on the sucrose density gradient. 5. The latency of the enzyme in vitro, as shown by the effect of the detergent Triton X-100, is discussed in relation to the proposed heterogeneity of UDP glucuronyltransferase.

Distribution of the multiple molecular forms of glucose-6-phosphate dehydrogenase in different physiological states

1979 ◽  
Vol 57 (5) ◽  
pp. 396-401 ◽  
Author(s):  
Hsiao-Lin Chang ◽  
Darold Holten ◽  
Rom Karin
Keyword(s):  
Enzyme Activity ◽  
Mammary Gland ◽  
Rat Liver ◽  
Specific Activity ◽  
Molecular Forms ◽  
Polyacrylamide Gels ◽  
Multiple Molecular Forms ◽  
Pregnancy And Lactation ◽  
Enzyme Specific Activity ◽  
Glucose 6 Phosphate Dehydrogenase

The distribution of the multiple molecular forms of rat liver and mammary gland glucose-6-phosphate dehydrogenase was determined by electrophoresis on 5% polyacrylamide gels. In both of these organs, changes in the distribution of enzyme activity among the several forms was slight even when approximately 20- to 40-fold changes in enzyme specific activity were achieved by fasting-refeeding experiments (for liver) or during pregnancy and lactation (for mammary gland), it was concluded that the induction of glucose-6-phosphate dehydrogenase in these two organs occurs without any major redistribution among the multiple molecular forms of this enzyme.

Increase in lipoperoxides and prolyl hydroxylase activity in rat liver following chronic ethanol feeding

1990 ◽  
Vol 40 (5) ◽  
pp. 1015-1019 ◽  
Author(s):  
Yamada Sadako ◽  
Yamada Minoru ◽  
Murawaki Yoshikazu ◽  
Hirayama Chisato
Keyword(s):  
Rat Liver ◽  
Prolyl Hydroxylase ◽  
Chronic Ethanol ◽  
Hydroxylase Activity ◽  
Ethanol Feeding

scholarly journals Steroid glucuronyltransferases of rat liver. Properties of oestrone and testosterone glucuronyltransferases and the effect of ovariectomy, castration and administration of steroids on the enzymes

1977 ◽  
Vol 162 (3) ◽  
pp. 545-556 ◽  
Author(s):  
G S Rao ◽  
G Haueter ◽  
M L Rao ◽  
H Breuer
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Specific Activity ◽  
Normal Activity ◽  
Competitive Inhibitor ◽  
Female Rats ◽  
Male Rats ◽  
Prolonged Treatment ◽  
Microsomal Preparation ◽  
Ionic Detergent

1. Microsomal preparations from rat liver, kidney and intestine were tested for UDP-glucuronyltransferase activity by using oestrone, oestradiol-17 beta, oestriol, testosterone, cortisol, cortisone, corticosterone, aldosterone, tetrahydrocortisol and tetrahydrocortisone as substrates. The microsomal preparation from the liver glucuronidated oestrone, oestradiol-17 beta and testosterone. 2. The specific activity of the enzyme was significantly higher in livers from female rats than in those from male rats. 3. Testosterone was actively glucuronidated by both sexes. Cortisol, cortisone, corticosterone, aldosterone, tetrahydrocortisol and tetrahydrocortisone were not glucuronidated by any of the three tissues. 4. The non-ionic detergent Lubrol WX activates liver microsomal UDP-glucuronyltransferase 2-3-fold with oestrone and testosterone as substrates. 5. Oestrone glucuronyltransferase was inhibited by oestradiol-17 beta, predominantly competitively and by testosterone non-competitively. Bilirubin was a non-competitive inhibitor of oestrone glucuronidation. p-Nitrophenol had no effect. 6. Oestrone glucuronyltransferase could not be stimulated by either acute or prolonged treatment of animals with phenobarbital, whereas a single dose of 3-methylcholanthrene led to a moderate stimulation. 7. Ovariectomy leads to a 56% decrease in oestrone glucuronyltransferase activity; administration of oestradiol-17 beta induces the enzyme to normal activity after 12 days, and after 15 days the activity is twice the control value. Actinomycin D and cycloheximide block the oestradiol-17 beta-induced increase in enzyme activity. 8. Castration has no effect on the activity of testosterone glucuronyltransferase, nor does administration of testosterone influence enzyme activity. The results provide strong evidence for the existence of multiple steroid glucuronyltransferases in the liver of the rat.

Activities of the phosphatidylcholine biosynthetic enzymes in rat liver during development

1983 ◽  
Vol 61 (10) ◽  
pp. 1147-1152 ◽  
Author(s):  
Steven L. Pelech ◽  
Ellen Power ◽  
Dennis E. Vance
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Specific Activity ◽  
Perinatal Period ◽  
Choline Kinase ◽  
Specific Enzyme ◽  
Methyltransferase Activity ◽  
Specific Enzyme Activity ◽  
Ctp:Phosphocholine Cytidylyltransferase ◽  
Phosphatidylcholine Biosynthesis

The activities of the enzymes of rat hepatic phosphatidylcholine biosynthesis have been measured as a function of development in the rat (term, 23 days). During the last 5 days of gestation, the specific activity of choline kinase was elevated almost fivefold (p < 0.05). After parturition, choline kinase activity was reduced to adult values by the 5th postnatal day. Over 75% of the total CTP:phosphocholine cytidylyltransferase protein in prenatal liver was detected in the cytosolic fraction. On the day of birth, most of the cytidylyltransferase translocated to the microsomes so that the microsomal specific enzyme activity was 3.3-fold higher (p < 0.01) and the cytosolic specific enzyme activity (measured in the presence of phospholipid) was 68% lower (p < 0.001) than the day before parturition. CDPcholine:diacylglycerol cholinephosphotransferase activity (measured in the presence of diacylglycerol) increased 130-fold (p < 0.001) during the last 5 days of gestation. On the 10th postnatal day, cholinephosphotransferase activity was 1.7-fold higher (p < 0.001) than immediately after birth, but declined to adult values by the 19th day. Between the 5th day prior to parturition and the 10th postnatal day, phosphatidylethanolamine N-methyltransferase activity steadily increased 16-fold (p < 0.001). The results are in agreement with the hypothesis that the increase in phosphatidylcholine in rat liver during the perinatal period is due to an increased synthesis of CDPcholine, which is a consequence of the translocation of the cytidylyltransferase from cytosol to the endoplasmic reticulum.

scholarly journals BENZPYRENE HYDROXYLASE ACTIVITY IN ISOLATED PARENCHYMAL AND NONPARENCHYMAL CELLS OF RAT LIVER

1972 ◽  
Vol 52 (2) ◽  
pp. 316-321 ◽  
Author(s):  
Elroy Cantrell ◽  
Edward Bresnick
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Steroid Metabolism ◽  
Hydroxylase Activity ◽  
Adult Rats ◽  
Polycyclic Hydrocarbons ◽  
Nonparenchymal Cells ◽  
Parenchymal Cells ◽  
Benzpyrene Hydroxylase

Previous studies have implicated the reticuloendothelial cells of the liver in certain aspects of steroid metabolism. The similarity in the metabolism of steroids and polycyclic hydrocarbons suggested that the nonparenchymal cells possibly play a role in these areas. The present study presents evidence that at least one of the microsomal NADPH-requirig enzymes, benzpyrene hydroxylase, is present in nonparenchymal cells and, furthermore, is "inducible." In adult rats treated with 3-methylcholanthrene or ß-naphthoflavone, the nonparenchymal cells exhibited increases in benzpyrene hydroxylase activity of 17-fold and five-fold, respectively. Treatment with phenobarbital resulted in only a slight increase in enzyme activity. Enzyme activity in parenchymal cells under similar conditions was increased sixfold and fivefold by 3-methylcholanthrene and ß-naphthoflavone, respectively, but not by phenobarbital.

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