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B Burchell

Publications and source records attributed to B Burchell.

At least 181 records · Page 10Linked to original sources
PubMed1979

Stimulation of defective Gunn-rat liver uridine diphosphate glucuronyltransferase activity in vitro by alkyl ketones.

Addition of alkyl ketone (10mM) to Gunn-rat liver homogenates increased UDP-glucuronyltransferase activity towards 2-aminophenol by 10--20 fold, up to enhanced values of enzyme activity observed with similarly treated Wistar-rat liver homogenates. Alkyl ketones also activate the defective enzyme purified from Gunn-rat liver. This genetic deficiency of UDP-glucuronyltransferase activity is no longer apparent when assayed in the presence of alkyl ketones.

Aminophenols↗
PubMed1979

Purification of mouse liver UDPglucuronosyltransferase.

The present study describes a method for the purification of hepatic microsomal UDPglucuronosyltransferase from two different strains of mice, by a combination of detergent solubilization, ion-exchange chromatography and affinity chromatography. Using this procedure up to 0.5 mg of UDPglucuronosyltransferase could be obtained from 30 g of mouse liver and this enzyme could be purified from as little as 10 g of mouse liver. The molecular weight of the apparently homogeneous preparation was 57 000 +/- 2 000 when determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The purified transferase catalysed the glucuronidation of approx. 0.6 mumol 4-nitrophenol min-1. mg-1 protein. Immunochemical analysis of this preparation further indicates that UDPglucuronosyltransferase has been purified to apparent homogeneity.

Animals↗
PubMed1978

Substrate specificity and properties of uridine diphosphate glucuronyltransferase purified to apparent homogeneity from phenobarbital-treated rat liver.

1. The purification to homogeneity of stable highly active preparations of UDP-glucuronyltransferase from liver of phenobarbital-treated rats is briefly described. 2. A single polypeptide was visible after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, of mol.wt.57000. 3. Antiserum raised against the pure enzyme produces a single sharp precipitin line after Ouchterlony double-diffusion analysis. 4. The pure UDP-glucuronyltransferase isolated from livers of untreated and phenobarbital-pretreated rats appears to be the same enzyme. 5. The Km (UDP-glucuronic acid) of the pure enzyme is 5.4 mM. 6. The activity of the pure enzyme towards 2-aminophenol can still be activated 2-3-fold by diethylnitrosamine. 7. UDP-glucose and UDP-galacturonic acid are not substrates for the purified enzyme. 8. The final preparation catalysed the glucuronidation of 4-nitrophenol, 1-naphthol, 2-aminophenol, morphine and 2-aminobenzoate. 9. Activities towards 4-nitrophenol, 1-naphthol and 2-aminophenol were all copurified. The proposed heterogeneity of UDP-glucuronyltransferase is discussed.

Animals↗
PubMed1978

Phospholipid content and activity of pure uridine diphosphate-glucuronyltransferase from rat liver.

Rat liver phospholipids were radioactively labeled in vivo before purification of UDP-glucuronyltransferase to homogeneity. The pure enzyme contained very little phospholipid (approx. 0.7 mol of phospholipid/mol of protein). The solubilization detergent Lubrol 12A9 appeared to act as a phospholipid substitute, capable of supporting UDP-glucuronyltransferase activity. Phospholipase C did not inhibit the pure enzyme activity and pure UDP-glucuronyltransferase was stimulated by 40--100% by the addition of phospholipid dispersions.

Animals↗
PubMed1977

A simple method for purification of epoxide hydratase from rat liver.

Rat liver epoxide hydratase was purified 460-fold to homogeneity by detergent solubilization and ion-exchange chromatography. The enzyme obtained in high yield (36%) exhibited a specific activity of 479nmol of styrene glycol formed/min per mg of protein, with styrene oxide as substrate. Only one polypeptide-staining band, mol.wt. 49500, was visible after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis.

Animals↗
PubMed1977

Studies on the purification of rat liver uridine diphosphate glucuronyltransferase.

1. A stable, more highly purified, preparation of UDP-glucuronyltransferase was obtained than previously reported. 2. Enzyme activity towards o-aminophenyl and p-nitrophenyl was increased 43- and 46-fold respectively. 3. The final preparation contains only three staining polypeptide bands visible after sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. 4. The only known major accompanying protein appears to be epoxide hydratase. 5. The purified enzyme activity towards o-aminophenol can still be activated 3 fold by diethylnitrosamine. 6. On evidence from purification, o-aminophenol and p-nitrophenol appear to be glucuronidated by the same enzyme protein. The possible recognition of the UDP-glucuronyltransferase enzyme is discussed.

Aniline Compounds↗
PubMed1976

Latency of epoxide hydratase and its relationship to that of UDPglucuronyltransferase.

Epoxide hydratase activity in liver microsomal preparations from adult made rats is latent to a slight extent. Maximal activations with neutral or anionic detergents were 30-60% whilst UDPglucuronyltransferase was maximally activated by 160-830% by the same detergents. Activation of microsomal epoxide hydratase requires much higher amounts of neutral or anionic detergents than activation of microsomal UDPglucuronyltransferase. High concentrations of inorganic salt, sonication or freeze-thawing which activate microsomal UDPglucuronyltransferase have no influence on microsomal epoxide hydratase activity. From this it appears that the activation which may involve either removal of a permeability barrier or release from conformational restraint occurs more easily for UDPglucuronyltransferase than for epoxide hydratase and that the activation of microsomal epoxide hydratase requires breakage of some hydrophobic bonds between the enzyme and membrrane component(s).

Animals↗
PubMed1975

Delayed induction by phenobarbital of udp-glucuronyltransferase activity towards bilirubin in fetal liver.

Phenobarbital pretreatment of pregnant mice (ASH/TO strain) gave rise to approximately equal concentrations of phenobarbital in both maternal and fetal liver. This pretreatment resulted in increased UDP-glucuronyltransferase (GT) activity towards bilirubin in maternal and neonatal liver in fetal liver on days 19 and 20 but in livers from earlier (15-18 day) fetuses GT either was not significantly increased or remained undetectable. Fetal liver is thus not competent to respond to phenobarbital by increasing its GT activity, until just before birth. This pattern persisted through changes in assay conditions and is contrasted with that occuring in embryos free from maternal influence. GT from adult and neontal liver is activated by 0.2 per cent digitonin; in fetal liver this response also does not appear until day 19.

Animals↗
PubMed1975

Relationship beteen activation of "detoxicating" enzymes in stored broken-cell preparations and in autolysing liver.

Activity of UDP-glucuronyltransferase (GT) towards o-aminophenol, p-nitrophenol and bilirubin has been followed in portions of mouse liver stored for periods up to 24 h and in mouse-liver homogenates stored under similar conditions of time and temperature. In both preparations and for all three substrates the pattern of change of GT activity was closely similar. Activity decreased initially, then rose to an optimum higher than in fresh tissue before finally falling. Overall glucuronidation, as measured in slices, also follwed this pattern. The effect of cycloheximide and of detergents, and the levels of UDP-glucose dehydrogenase, UDP-glucuronic acid and aniline hydroxylase were also studied. It is concluded that autolysing liver tissue passes through a period of increased GT activity and glucuronidation corresponding in onset with spontaneous activation of GT in stored homogenates and probably originating by a similiar mechanism. This increase contrasts with progressive fall in hydroxylating activity. The latency of GT in vivo and the value of its activation in damaged liver are discussed.

Aniline Hydroxylase↗