scholarly journals Some properties of the uridine diphosphate glucuronyltransferase activity synthesizing thio-β-d-glucuronides

1973 ◽  
Vol 131 (1) ◽  
pp. 139-147 ◽  
Author(s):  
H. P. A. Illing ◽  
G. J. Dutton
Keyword(s):  
Enzyme Activity ◽  
Phenolic Compounds ◽  
Organ Culture ◽  
Tissue Distribution ◽  
Glucuronic Acid ◽  
Uridine Diphosphate ◽  
Intracellular Location ◽  
Gunn Rats ◽  
Optimum Ph

1. Some properties of the UDP-glucuronyltransferase synthesizing thio-β-d-glucuronides were investigated and compared with those of the enzyme synthesizing the O-glucuronides of analogous phenols. 2. Enzyme activity was generally similar for both classes of substrate in tissue distribution, intracellular location, optimum pH, perinatal development and induction by organ culture or by phenobarbital. 3. Certain differences were noted between the two types of activity in behaviour on storage and on activation, in kinetic behaviour and in distribution between Wistar and Gunn rats; the Gunn rats were not deficient in hepatic UDP-glucuronyltransferase activity towards o-aminothiophenol. 4. These differences are no greater than those exhibited in the synthesis of various O-glucuronides; therefore thiolic substrates could compete in vivo with phenolic compounds for access to the UDP-glucuronyltransferase complex as well as for UDP-glucuronic acid.

scholarly journals QUANTITATIVE AND HISTOCHEMICAL STUDIES ON THE DESORPTION AND READSORPTION OF ALDOLASE IN CROSS-STRIATED MUSCLE

1969 ◽  
Vol 17 (5) ◽  
pp. 314-320 ◽  
Author(s):  
H. ARNOLD ◽  
J. NOLTE ◽  
D. PETTE
Keyword(s):  
Enzyme Activity ◽  
Actin Filaments ◽  
Phosphate Buffer ◽  
Striated Muscle ◽  
Psoas Muscle ◽  
Histochemical Staining ◽  
Intracellular Location ◽  
Successive Extraction ◽  
Complete Extraction

Complete extraction of aldolase from minced rabbit psoas muscle was achieved by successive extraction steps in 0.1 M phosphate buffer. Aldolase was then readsorbed quantitatively to the depleted myofibrils. Extraction, readsorption and a final redsorption of the enzyme were followed quantitatively by enzyme activity determinations and qualitatively by histochemical staining of aldolase. The intracellular location of the readsorbed enzyme was found to be identical with that of aldolase in native muscle. In both cases, aldolase was localized within the isotropic bands. These results as well as the previously demonstrated binding of the enzyme to F-actin suggest that aldolase is located within the interfilamentary sarcoplasm of the isotropic bands and is probably also bound in vivo to the actin filaments.

scholarly journals The effect of steroids and nucleotides on solubilized bilirubin uridine diphosphate glucuronyltransferase

1970 ◽  
Vol 119 (3) ◽  
pp. 437-445 ◽  
Author(s):  
B. P. F. Adlard ◽  
G. H. Lathe
Keyword(s):  
Enzyme Activity ◽  
Glucuronic Acid ◽  
Liver Microsomes ◽  
Fold Increase ◽  
Rat Liver Microsomes ◽  
Uridine Diphosphate ◽  
Competitive Effects ◽  
Solubilized Enzyme ◽  
High Concentrations ◽  
Solubilized Form

1. It was confirmed that bilirubin glucuronyltransferase can be obtained in solubilized form from rat liver microsomes. 2. Michaelis–Menten kinetics were not followed by the enzyme with bilirubin as substrate when the bilirubin/albumin ratio was varied. High concentrations of bilirubin were inhibitory. 3. The Km for UDP-glucuronic acid at the optimum bilirubin concentration was 0.46mm. 4. Low concentrations of Ca2+ were inhibitory in the absence of Mg2+ but stimulatory in its presence; the converse applied for EDTA. 5. UDP-N-acetylglucosamine and UDP-glucose enhanced conjugation by untreated, but not by solubilized microsomes. 6. The apparent 9.5-fold increase in activity after solubilization was probably due to the absence of UDP-glucuronic acid pyrophosphatase activity in the solubilized preparation. 7. The activation of solubilized enzyme activity by ATP was considered to be a result of chelation of inhibitory metal ions. 8. The solubilized enzyme activity was inhibited by UMP and UDP. The effect of UMP was not competitive with respect to UDP-glucuronic acid. 9. A number of steroids inhibited the solubilized enzyme activity. The competitive effects of stilboestrol, oestrone sulphate and 3β-hydroxyandrost-5-en-17-one, with respect to UDP-glucuronic acid, may be explained on an allosteric basis.

Modulative Effects of Metabolic Effectors on Benzo(A)Pyrene-Induced Cytotoxicity and Mutagenicity in Mammalian Cells

1994 ◽  
Vol 10 (3) ◽  
pp. 181-189 ◽  
Author(s):  
Abraham W. Hsie ◽  
Leslie Recio
Keyword(s):  
Mammalian Cells ◽  
Glucuronic Acid ◽  
Chinese Hamster ◽  
Ovary Cell ◽  
Future Research ◽  
Uridine Diphosphate ◽  
Glucuronide Conjugation ◽  
Hypoxanthine Guanine Phosphoribosyltransferase ◽  
Mutagenic Effects

Conjugation and detoxification of mixed function oxidase (MFO)-mediated benzo(a)pyrene [B(a)P] metabolites with glucuronic acid and glutathione (GSH) are major pathways of B(a)P elimination and ultimately excretion in vivo. We have studied the effects of uridine diphosphate α-D-glucuronic acid (UDPGA) and GSH, a cofactor for the synthesis of glucuronide and GSH conjugates, respectively, on B(a)P-induced cytotoxicity and mutagenicity in mammalian cells. The S9-mix used in the Chinese hamster ovary cell/hypoxanthine-guanine phosphoribosyltransferase (CHO/HPRT) mutational assay was supplemented with either UDPGA, GSH, or GSH plus purified GSH-S-transferases (GSHTs), to study modulation of glucuronide and GSH detoxification mechanisms on B(a)P-induced cytotoxic and mutagenic effects. We found that the addition of UDPGA to S9-mix reduces cytotoxicity induced by either B(a)P or B(a)P 6-OH but not by B(a)P 7,8-diol [B(a)P-diol]. The reduction of B(a)P and B(a)P 6-OH-induced cytotoxicity by glucuronide conjugation is likely due to elimination of cytotoxic phenols and quinones. The addition of GSH to the S9-mix resulted in a reduction of B(a)P- and B(a)P-diol-induced cytotoxicity. GSH plus GSHT reduced B(a)P-induced cytotoxicity and mutagenicity. GSH inhibited the mutagenicity at low concentrations of B(a)P-diol. GSH plus GSHTs inhibited the cytotoxicity and mutagenicity of B(a)P-diol at concentrations not affected by GSH alone. These studies demonstrate that mechanisms of detoxification can affect the biological activity of B(a)P and B(a)P-diol as profoundly as bioactivation by the MFO system. Future research should address studies of mutagenicity modulation by metabolic effectors at both the molecular (DNA sequence) and cellular (quantitative mutagenesis) level.

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

1978 ◽  
Vol 171 (3) ◽  
pp. 821-824 ◽  
Author(s):  
B Burchell ◽  
T Hallinan
Keyword(s):  
Enzyme Activity ◽  
Phospholipase C ◽  
Rat Liver ◽  
Phospholipid Content ◽  
Uridine Diphosphate

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.

The hyperbilirubinemic Gunn rat is resistant to the pressor effects of angiotensin II

2005 ◽  
Vol 288 (3) ◽  
pp. F552-F558 ◽  
Author(s):  
Axel Pflueger ◽  
Anthony J. Croatt ◽  
Timothy E. Peterson ◽  
Leslie A. Smith ◽  
Livius V. d'Uscio ◽  
...  
Keyword(s):  
Superoxide Anion ◽  
Antioxidant Properties ◽  
Chronic Administration ◽  
In Vivo Studies ◽  
Uridine Diphosphate ◽  
Ang Ii ◽  
Gunn Rat ◽  
Gunn Rats

ANG II induces vasoconstriction, at least in part, by stimulating NADPH oxidase and generating reactive oxygen species. ANG II also induces heme oxygenase activity, and bilirubin, a product of such activity, possesses antioxidant properties. We hypothesized that bilirubin, because of its antioxidant properties, may reduce the pressor and prooxidant effects of ANG II. Our in vivo studies used the hyperbilirubinemic Gunn rat which is deficient in the enzyme uridine diphosphate glucuronosyl transferase, the latter enabling the excretion of bilirubin into bile. ANG II (0.5 mg·kg−1·day−1) or saline vehicle was administered by osmotic minipump to control and Gunn rats for 4 wk. The rise in systolic blood pressure induced by ANG II, as observed in control rats, was markedly reduced in Gunn rats, the latter ∼50% less at 3 and 4 wk after the initiation of ANG II infusion. The chronic administration of ANG II also impaired endothelium-dependent relaxation responses in control rats but not in Gunn rats. As assessed by the tetrahydrobiopterin/dihydrobiopterin ratio, ANG II induced oxidative stress in the aorta in control rats but not in Gunn rats. Heightened generation of superoxide anion in aortic rings in ANG II-infused rats and by vascular smooth muscle cells exposed to ANG II was normalized by bilirubin in vitro. We conclude that the pressor and prooxidant effects of ANG II are attenuated in the hyperbilirubinemic Gunn rat, an effect which, we speculate, may reflect, at least in part, the scavenging of superoxide anion by bilirubin.

scholarly journals DEVELOPMENT OF PHENOBARBITAL-SENSITIVE CONTROL MECHANISMS FOR URIDINE DIPHOSPHATE GLUCURONYLTRANSFERASE ACTIVITY IN CHICK EMBRYO LIVER

1972 ◽  
Vol 55 (2) ◽  
pp. 448-456 ◽  
Author(s):  
Brian Burchell ◽  
Geoffrey J. Dutton ◽  
Andrew M. Nemeth
Keyword(s):  
Enzyme Activity ◽  
Chick Embryo ◽  
Organ Culture ◽  
Culture Medium ◽  
Developmental Changes ◽  
Regulatory Mechanisms ◽  
Control Mechanisms ◽  
Uridine Diphosphate ◽  
In Ovo ◽  
Embryo Liver

Uridine diphosphate (UDP) glucuronyltransferase activity in chick liver rises at hatching from near zero to adult levels. This rise will occur prematurely in embryo liver during organ culture. Increase in enzyme activity during organ culture differs with embryo age: in liver from 11-day old embryos it ceases at adult values; in liver from 5-day old embryos it continues to much higher-than-adult levels. Phenobarbital added to culture medium accelerates these rises in enzyme activity and elevates the plateau reached in 11-day embryo liver to that observed in 5-day embryo liver. Kinetic analysis of the changes in enzyme activity induced by phenobarbital during culture suggests that the regulatory mechanisms for enzyme activity are different in 5- and 11-day embryo liver and that these differences reflect developmental changes occurring in ovo.

Regulation of the diurnal cycle in activity of serotonin acetyltransferase in the chick pineal gland

1978 ◽  
Vol 56 (7) ◽  
pp. 685-690 ◽  
Author(s):  
S. D. Wainwright ◽  
Lillian K. Wainwright
Keyword(s):  
Enzyme Activity ◽  
Organ Culture ◽  
Pineal Gland ◽  
Diurnal Cycle ◽  
Adenosine Receptor ◽  
Control Mechanism ◽  
Negative Control ◽  
Acetyltransferase Activity ◽  
In Vivo Effects

When chick pineal glands were explanted into organ culture at midlight phase of a diurnal cycle of illumination and incubated in the dark, they developed marked increases in serotonin acetyltransferase (acetyl coA:arylamine N-acetyltransferase; EC 2.3.1.5) activity. Either this increase in activity was inhibited or its onset was retarded in glands incubated under constant illumination.Supplements of theophylline, isobutylmethylxanthine, quinidine, and compound Ro 20-1724 (4-(3-butoxyl-4-methoxybenzyl)-2-imidazolidinone) elicited very marked increases in serotonin acetyltransferase activity in glands cultured in the dark. Levels of activity attained after 6 h in culture approached or exceeded the maximum levels attained at middark phase of the diurnal cycle in vivo. Effects of theophylline and compound Ro 20-1724 were additive.Supplements of dibutryl cAMP had little or no effect upon levels of serotonin acetyltransferase activity when tested alone or in combination with theophylline but further enhanced the increase in the level of enzyme activity elicited by Ro 20-1724. Adenosine and cAMP had little or no effect upon levels of serotonin acetyltransferase activity.It is concluded that levels of serotonin acetyltransferase activity in the chick pineal gland are regulated by a repressive, negative-control mechanism, which probably involves a membranous adenosine receptor.

scholarly journals Regulation of tyrosine aminotransferase in foetal rat liver

1980 ◽  
Vol 186 (2) ◽  
pp. 609-612 ◽  
Author(s):  
S M Andersson ◽  
N C Räihä ◽  
J J Ohisalo
Keyword(s):  
Enzyme Activity ◽  
Methyl Ester ◽  
Cyclic Amp ◽  
Organ Culture ◽  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Dibutyryl Cyclic Amp ◽  
Adult Rat ◽  
Foetal Rat

A specific tyrosine aminotransferase, separate from the aspartate aminotransferases, is present in low concentration in foetal rat liver at the 21st day of gestation. Intraperitoneal injections of tyrosine methyl ester into the foetuses in utero increase the activity 2-fold, whereas glucose injections decrease it. Tyrosine, dexamethasone and dibutyryl cyclic AMP induce the enzyme activity in organ culture to the same extent as in adult rat liver in vivo.

scholarly journals Multiple N-acetyltransferases and drug metabolism. Tissue distribution, characterization and significance of mammalian N-acetyltransferase

1973 ◽  
Vol 132 (3) ◽  
pp. 519-526 ◽  
Author(s):  
D. J. Hearse ◽  
W. W. Weber
Keyword(s):  
Enzyme Activity ◽  
Drug Metabolism ◽  
Tissue Distribution ◽  
Aminobenzoic Acid ◽  
Slow Acetylator ◽  
Wide Range ◽  
Extrahepatic Tissues ◽  
The Individual

Investigations in the rabbit have indicated the existence of more than one N-acetyltransferase (EC 2.3.1.5). At least two enzymes, possibly isoenzymes, were partially characterized. The enzymes differed in their tissue distribution, substrate specificity, stability and pH characteristics. One of the enzymes was primarily associated with liver and gut and catalysed the acetylation of a wide range of drugs and foreign compounds, e.g. isoniazid, p-aminobenzoic acid, sulphamethazine and sulphadiazine. The activity of this enzyme corresponded to the well-characterized polymorphic trait of isoniazid acetylation, and determined whether individuals were classified as either `rapid' or `slow' acetylators. Another enzyme activity found in extrahepatic tissues readily catalysed the acetylation of p-aminobenzoic acid but was much less active towards isoniazid and sulphamethazine. The activity of this enzyme remained relatively constant from individual to individual. Studies in vitro and in vivo with both `rapid' and `slow' acetylator rabbits revealed that, for certain substrates, extrahepatic N-acetyltransferase contributes significantly to the total acetylating capacity of the individual. The possible significance and applicability of these findings to drug metabolism and acetylation polymorphism in man is discussed.

Sign in / Sign up

Export Citation Format

Share Document