scholarly journals The properties of uridine diphosphate glucuronyltransferase(s) which catalyse the synthesis of steroid glucuronides in microsomal fractions from guinea-pig liver

1976 ◽  
Vol 157 (3) ◽  
pp. 667-673 ◽  
Author(s):  
D Zakim ◽  
D A Vessey
Keyword(s):  
Guinea Pig ◽  
Glucuronic Acid ◽  
Large Family ◽  
Uridine Diphosphate ◽  
Bivalent Metal ◽  
Pig Liver ◽  
Bivalent Metal Ions ◽  
Triton X ◽  
Related Proteins ◽  
Guinea Pig Liver

The properties of the UDP-glucuronyltransferase(s) of guinea-pig liver that catalyse the synthesis of steroid glucuronides were examined. There are many similarities between apparently different substrate-specific forms of these enzymes in that all are activated by bivalent metal ions, and all contain at least 2 thiol groups important for enzyme activity. On the other hand, there are significant differences between the enzymes conjugating steroids and those conjugating non-steroids. Only the latter are activated by UDP-N-acetylglucosamine, which enhances their relatively poor affinity for UDP-glucuronic acid. The steroid-conjugating forms of UDP-glucuronyltransferase are not activated by UDP-N-acetylglucosamine and have relatively high apparent affinities for UDP-glucuronic acid. The rate of glucuronidation of testosterone was inhibited by treatment with phospholipase A. Treatment with cholate or Triton X-100 did not enhance the rates of glucuronidation of any steroid tested. The data indicate several similarities between different forms of UDP-glucuronyltransferase, suggesting that there is a large family of related proteins. At the same time there are important differences in the parameters that modulate the rates of different glucuronidation reactions.

Effects of non-ionic and anionic detergents on lipid-associated tissue ferritin.

1988 ◽  
Vol 34 (1) ◽  
pp. 152-154
Author(s):  
B E Cham ◽  
P Roeser ◽  
A Nikles
Keyword(s):  
Guinea Pig ◽  
Liver Homogenate ◽  
Diisopropyl Ether ◽  
Detergent Concentration ◽  
Pig Liver ◽  
Ionic Detergents ◽  
Ionic Detergent ◽  
Anionic Detergents ◽  
Triton X ◽  
Guinea Pig Liver

Abstract Lipid-associated ferritin from homogenates of guinea pig liver is released from its conjugate(s) by incubation with the non-ionic detergents Triton X-100 and Nonidet P-40 but not by incubation with the anionic detergent deoxycholate. The amount of lipid-associated ferritin released from its conjugate(s) depends on the concentration of the non-ionic detergents. At a final non-ionic detergent concentration of about 20 g/L, all lipid-associated ferritin is released from its conjugate(s) in a liver homogenate. The amount released is identical with the amount of the lipid-associated ferritin obtained by extraction of the same liver homogenate with a mixture of butanol and diisopropyl ether.

scholarly journals A rapid enzymic procedure for the determination of picomole amounts of UDP-glucuronic acid

1980 ◽  
Vol 189 (2) ◽  
pp. 369-372 ◽  
Author(s):  
J Singh ◽  
L R Schwarz ◽  
F J Wiebel
Keyword(s):  
Guinea Pig ◽  
Glucuronic Acid ◽  
Cultured Cells ◽  
Cellular Protein ◽  
Pig Liver ◽  
Guinea Pig Liver

A simple microassay for the determination of UDP-glucuronic acid was developed on the basis of the formation of benzo[a]pyrene 3-glucuronide catalysed by UDP-glucuronyltransferase of guinea-pig liver. As little as 1-5 pmol of UDP-glucuronic acid was detectable in extracts of heat-denatured probes of liver or cultured cells equivalent to 10-50 micrograms of cellular protein.

Reduced Levels of Uridine Diphosphate Glucose Pyrophosphorylase Activity in Fetal and Neonatal Human and Guinea Pig Liver

Neonatology ◽  
1989 ◽  
Vol 56 (3) ◽  
pp. 174-180
Author(s):  
G. Vaca ◽  
L.P. Castro-Félix ◽  
C. Medina ◽  
M.D. Medina ◽  
R. Blancarte ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Uridine Diphosphate ◽  
Pig Liver ◽  
Uridine Diphosphate Glucose ◽  
Diphosphate Glucose ◽  
Guinea Pig Liver

scholarly journals Assay and properties of digitonin-activated bilirubin uridine diphosphate glucuronyltransferase from rat liver

1972 ◽  
Vol 129 (3) ◽  
pp. 605-618 ◽  
Author(s):  
K. P. M. Heirwegh ◽  
M. Van De Vijver ◽  
J. Fevery
Keyword(s):  
Rat Liver ◽  
Metal Ion ◽  
Glucuronic Acid ◽  
Uridine Diphosphate ◽  
Bivalent Metal ◽  
Bivalent Metal Ions ◽  
Liver Homogenates ◽  
Cell Fractions ◽  
Biliary Excretion Rate ◽  
Substrate Concentrations

1. The bilirubin UDP-glucuronyltransferase assay described by Van Roy & Heirwegh (1968) has been improved. 2. Extraction of final azo-derivatives is rendered more simple and efficient by thorough emulsification and by cooling. 3. Pretreatment of homogenates and cell fractions with digitonin increases the sensitivity of the assays and gives less variable results than those with untreated preparations. The activation procedure is flexible. 4. Blank values (obtained from incubation mixtures from which activating bivalent metal ion and UDP-glucuronic acid were omitted) are low. No endogenous conjugate formation could be detected except with untreated, fresh liver homogenates. Control incubation mixtures containing the latter preparations are preferably kept at 0°C. 5. With activated microsomal preparations, rates of breakdown of UDP-glucuronic acid (as monitored by release of Pi) were low. Little if any increase in enzyme activity was found when UDP-N-acetylglucosamine was included in the incubation mixtures. 6. Slight deviation from Michaelis–Menten kinetics with respect to bilirubin observed at low substrate concentrations is probably related to the use of binding protein in the assay mixtures. Michaelis–Menten kinetics were followed with respect to UDP-glucuronic acid. Part of the enzyme in microsomal preparations from rat liver functioned independently of added bivalent metal ions. Mn2+ was slightly more, and Ca2+ somewhat less, stimulatory than Mg2+. The Mg2+-dependent fraction showed Michaelis–Menten kinetics with respect to the added Mg2+. 7. The enzyme activities found were higher than values reported in the literature for untreated or purified preparations from rat liver. They were above reported values of the maximal biliary excretion rate of bilirubin.

scholarly journals Glucuronidation of 3-O-methylnoradrenaline, harmalol and some related compounds

1968 ◽  
Vol 110 (1) ◽  
pp. 99-104 ◽  
Author(s):  
Kim Ping Wong ◽  
Theodore L. Sourkes
Keyword(s):  
Guinea Pig ◽  
Glucuronic Acid ◽  
Enzymic Activity ◽  
Microsomal Preparation ◽  
Pig Liver ◽  
Related Compounds ◽  
Substrate Concentrations ◽  
Guinea Pig Liver

1. The following compounds were glucuronidated in the presence of UDP-glucuronic acid and a microsomal preparation made from guinea-pig liver: 14C-labelled 3-O-methyladrenaline, 3-O-methylnoradrenaline, 3-methoxytyramine and 4-hydroxy-3-methoxyphenethanol, as well as unlabelled harmalol and harmol. 2. [14C]Homovanillic (4-hydroxy-3-methoxyphenylacetic) acid was not a substrate for the microsomal glucuronyltransferase. 3. The Km values for harmalol and harmol were 0·69×10−4m and 0·50×10−4m respectively. 4. The Km values for UDP-glucuronic acid, in the presence of 14C-labelled 3-O-methylnoradrenaline, harmalol and harmol as aglycones, were 0·57×10−4m, 0·44×10−4m and 2·20×10−4m respectively. 5. Mg2+ added at 2·5–10mm activated glucuronyltransferase, with harmalol as substrate. Concentrations above 10mm inhibited the enzymic activity. 6. The overall, or net, transglucuronidating activity of microsomal preparations of the liver, with harmalol as substrate, was greatest for guinea pig, and very much lower for rabbit, mouse and rat.

scholarly journals The availability of carnitine acetyltransferase in mitochondria from guinea-pig liver and other tissues

1968 ◽  
Vol 110 (4) ◽  
pp. 739-746 ◽  
Author(s):  
P. J. Barker ◽  
N. J. Fincham ◽  
D C Hardwick
Keyword(s):  
Guinea Pig ◽  
Glutamate Dehydrogenase ◽  
Freeze Drying ◽  
Enzymic Activity ◽  
Carnitine Acetyltransferase ◽  
Cell Cytoplasm ◽  
Pig Liver ◽  
Triton X ◽  
Guinea Pig Liver

The carnitine acetyltransferase and glutamate dehydrogenase activities of guinea-pig liver and other tissues were estimated. Both enzymes are wholly mitochondrial, and can only be fully observed after disruption of the mitochondrion. Triton X-100 (0·1%) or freeze-drying revealed more activity than other methods tried. In mitochondria prepared and suspended in 0·25m-sucrose and in cell cytoplasm only small fractions of the total enzymic activity could be observed in guinea-pig liver: on average 7·5% of carnitine acetyltransferase and 5·5% of glutamate dehydrogenase. It is concluded that, in liver or mammary gland of goat, guinea pig or rat, little or no carnitine acetyltransferase is available in vivo to acetyl-CoA outside the mitochondrion.

scholarly journals Biliary excretion of cyclohexylphenyl 4-[35S]sulphate in the guinea pig

1978 ◽  
Vol 176 (2) ◽  
pp. 443-448
Author(s):  
G M Powell ◽  
A H Olavesen ◽  
C G Curtis
Keyword(s):  
Molecular Weight ◽  
Guinea Pig ◽  
Biliary Excretion ◽  
Glucuronic Acid ◽  
Intact Animal ◽  
Relative Concentration ◽  
Metabolic Fate ◽  
Pig Liver ◽  
Acid Conjugate ◽  
Guinea Pig Liver

The metabolic fate and mode of excretion of cyclohexylphenyl 4-[35S]sulphate were studied in the guinea pig. Up to 54.8% of the dose appeared in the bile, the majority as unchanged ester. Substantial amounts of hydroxylated cyclohexylphenyl 4-[35S]sulphate were also excreted in the bile together with minor amounts of the corresponding glucuronic acid conjugate. When isolated guinea-pig livers were perfused with cyclohexylphenyl 4-[35S]sulphate the biliary components were the same as those in the intact animal, although the relative concentration of the hydroxylated derivative was significantly greater. When the hydroxylated derivative was re-injected into guinea pigs it was excreted almost entirely unchanged in the bile. However, in the rat, it was excreted in the bile as a glucuronic acid conjugate. These findings are discussed in relation to studies carried out in the rat [Hearse, Powell, Olavesen & Dodgson (1969) Biochem. Pharmacol. 18, 181–195] and to differences in enzyme activities in rat and guinea-pig liver. The results are also discussed in terms of the molecular-weight threshold for the excretion of anions in guinea-pig bile.

scholarly journals Effect on uridine diphosphate glucuronyltransferase activity of depleting and restoring phospholipids to guinea-pig liver microsomal preparations

1976 ◽  
Vol 154 (3) ◽  
pp. 783-785 ◽  
Author(s):  
C S. Berry ◽  
M Caldecourt ◽  
T Hallinan
Keyword(s):  
Guinea Pig ◽  
Uridine Diphosphate ◽  
Pig Liver ◽  
Conformationally Constrained ◽  
Guinea Pig Liver ◽  
Do So

Phospholipid depletion substantially inhibited the maximum demonstrable activities of the forward (glucuronidation) and reverse reactions of UDP-glucuronyltransferase towards p-nitrophenol in guinea-pig liver microsomal preparations. Dispersions of liver phospholipids restored activity, whereas non-phospholipid amphipaths failed to do so effectively. These results suggest that the system is probably phospholipid-dependent rather than conformationally constrained by phospholipids.

Sign in / Sign up

Export Citation Format

Share Document