scholarly journals Comparison in different species of biliary bilirubin-IX α conjugates with the activities of hepatic and renal bilirubin-IX α-uridine diphosphate glycosyltransferases

1977 ◽  
Vol 164 (3) ◽  
pp. 737-746 ◽  
Author(s):  
J Fevery ◽  
M Van de Vijver ◽  
R Michiels ◽  
K P M Heirwegh
Keyword(s):  
Glucuronic Acid ◽  
Mammalian Species ◽  
Liver Homogenate ◽  
Species Variation ◽  
Bile Pigment ◽  
Uridine Diphosphate ◽  
Ph Optimum ◽  
Equal Importance ◽  
Liver And Kidney

The bilrubin-IXalpha conjugates in bile and the activities of bilirubin-IX alphax–UDP-glycosyltransferases in liver and kidney were determined for ten species of mammals and for the chicken. 1. In the mammalian species, bilirubin-IX alpha glucuronide was the predominant bile pigment. Excretion of neutral glycosides was unimportant, except in the cat, the mouse, the rabbit and the dog, where glucose and xylose represented 12–41% of total conjugating groups bound to bilirubin-IX alpha. In chicken bile, glucoside and glucuronide conjugates were of equal importance. They probably represent only a small fraction of the total bile pigment. 2. The transferase activities in liver showed pronounced species variation. This was also apparent with regard to activation by digitonin, pH optimum and relative activities of transferases acting on either UDP-glucuronic acid or neutral UDP-sugars. 3. Man, the dog, the cat and the rat excrete bilirubin-IX alpha largely as diconjugated derivatives. In general, diconjugated bilirubin-IX alpha could also be synthesized in vitro with liver homogenate, bilirubin-IX alpha and UDP-sugar. In contrast, for the other species examined, bilirubin pigments consisted predominantly of monoconjugated bilirubin-IX alpha. Synthesis in vitro with UDP-glucuronic acid, UDP-glucose or UDP-xylose as the sugar donor led exclusively to the formation of monoconjugated bilirubin-IX alpha. 4. The transferase activities in the kidney were restricted to the cortex and were important only for the rat and the dog. No activity at all could be detected for several species, including man. 5. Comparison of the transferase activities in liver with reported values of the maximal rate of excretion in bile suggests a close linkage between conjugation and biliary secretion of bilirubin-IX alpha.

In Vitro Metabolism of 17β-Estradiol by Human Liver Tissue

1975 ◽  
Vol 53 (8) ◽  
pp. 903-906 ◽  
Author(s):  
R. Hobkirk ◽  
Joyce D. Mellor ◽  
Mona Nilsen
Keyword(s):  
Phosphate Buffer ◽  
Human Liver ◽  
Glucuronic Acid ◽  
Liver Homogenate ◽  
Uridine Diphosphate ◽  
Main Metabolite ◽  
Human Liver Tissue ◽  
17Β Estradiol ◽  
Human Liver Slices

17β-[6,7-3H]Estradiol was incubated with adult human liver slices in Krebs–Ringer phosphate buffer containing glucose. Of the identified 3H recovered, 51–76% consisted of estrone-3-sulfate (E13S) and 17β-estradiol-3-sulfate (E23S). E13S was the main metabolite and was found in both tissue and medium. E23S was present only in the medium. Minor amounts of estrogen glucuronides were formed. When a human liver homogenate was incubated with [3H]E2 in a medium fortified with excess uridine diphosphate glucuronic acid only some 4% of conjugation with glucuronic acid was observed. It is suggested that human liver favors sulfurylation as the conjugating mechanism for E2 and E1.

Studies on Carbohydrate Metabolism in Lizards

1972 ◽  
Vol 27 (12) ◽  
pp. 1531-1535 ◽  
Author(s):  
H. S. Ali Athar ◽  
S. Nazrul Hasnain ◽  
M. Zain-Ul-Abedin
Keyword(s):  
Blood Glucose ◽  
Carbohydrate Metabolism ◽  
Mammalian Species ◽  
Liver Homogenate ◽  
Titratable Acidity ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Concomitant Decrease ◽  
Liver And Kidney ◽  
Reducing Capacity

1. Initial glycogen levels in the liver were found to be significantly higher than in the kidneys of the two species studied. The glycogen levels in kidney were however considerably higher than in some mammalian species.2. Total reducing capacity, true glucose, saccharoid fraction and titratable acidity increase gradually with concomitant decrease in the glycogen levels when liver and kidney homogenates of uromastix and liver homogenate of varanus were incubated for a period of 4 hours.3. Total reducing capacity, true glucose and the titratable acidity increase gradually, while the glycogen and the saccharoid fraction remain unchanged when the kidney homogenates of varanus are incubated for 4 hours.4. Total reducing capacity, true glucose and saccharoid fraction in the blood of uromastix are higher than in varanus. The blood glucose levels in both the species are higher than found in the mammals

The Enzymic Phosphorylation of N6-(Δ2-Isopentenyl)adenosine in Chick Liver Homogenates

1973 ◽  
Vol 51 (10) ◽  
pp. 1341-1346 ◽  
Author(s):  
B. D. McLennan ◽  
A. Pater
Keyword(s):  
Biological Effects ◽  
Adenosine Kinase ◽  
Side Chain ◽  
Ph Optimum ◽  
Enzyme Preparations ◽  
Liver And Kidney ◽  
Isopentenyl Adenosine ◽  
Modified Nucleoside ◽  
Chick Tissue

Enzyme preparations from chick kidney and liver rapidly phosphorylate the modified nucleoside, N6-(Δ2-isopentenyl) adenosine. The resulting metabolite behaves electrophoretically as a mononucleotide and is quantitatively hydrolyzed to the nucleoside by 5′-nucleotidase. The isopentenyl side chain is not altered in the phosphorylated derivative. It is concluded that the metabolite is N6-(Δ2-isopentenyl) adenosine-5′-monophosphate. The properties of the enzyme activity responsible for the phosphorylation resemble the properties of adenosine kinase isolated from sarcoma-180 cells, and from rabbit liver, with respect to pH optimum, Km value, and sensitivity to magnesium ion and ATP. Thus, it seems probable that the phosphorylation observed in the chick tissue preparations is due to adenosine kinase. The mononucleotide could not be further phosphorylated in vitro by adenylate kinase. This observation, coupled with the fact that isopentenyladenosine is biosynthesized at the macromolecular level, suggests that the 5′-monophosphate ester may be the form through which some of the biological effects of this modified nucleoside are manifested.A major end product of N6-(Δ2-isopentenyl) adenosine catabolism in chick liver and kidney homogenates is uric acid.

scholarly journals Biosynthesis of glycosaminoglycans in bovine cornea. The effect of uridine diphosphate xylose

1970 ◽  
Vol 120 (4) ◽  
pp. 719-723 ◽  
Author(s):  
C. Balduini ◽  
A. Brovelli ◽  
A. A. Castellani
Keyword(s):  
Glucuronic Acid ◽  
Chondroitin Sulphate ◽  
Glucose Dehydrogenase ◽  
Uridine Diphosphate ◽  
Regulatory Effect ◽  
Keratan Sulphate ◽  
Polysaccharide Chain

1. The role of UDP-xylose in the regulation of corneal glycosaminoglycan biosynthesis was investigated. Bovine corneas were incubated with [U-14C]-glucose in the presence and in the absence of the nucleotide, and the radioactivity of chondroitin, chondroitin sulphate and keratan sulphate, as well as of their monosaccharide constituents, was determined. 2. A decrease in the rate of biosynthesis of chondroitin and chondroitin sulphate and an increase in that of keratan sulphate were observed in the samples incubated with UDP-xylose. 3. The UDP-glucuronic acid isolated after the incubation in the presence of UDP-xylose showed a noticeable decrease in the amount of radioactivity incorporated; this result suggests that UDP-xylose inhibits the UDP-glucose dehydrogenase, causing an accumulation of UDP-glucose and consequently an increase in the formation of UDP-galactose and keratan sulphate. 4. Galactose and galactosamine isolated from the polysaccharides showed variations in the amount of radioactivity incorporated in accordance with those observed for the macromolecules; this fact confirms that in the system we used in vitro a real biosynthesis of the polysaccharide chain took place and that the regulatory effect of UDP-xylose was active at the monosaccharide level.

scholarly journals Structures of bilirubin conjugates synthesized in vitro from bilirubin and uridine diphosphate glucuronic acid, uridine diphosphate glucose or uridine diphosphate xylose by preparations from rat liver

1972 ◽  
Vol 129 (3) ◽  
pp. 635-644 ◽  
Author(s):  
J. Fevery ◽  
P. Leroy ◽  
M. Van De Vijver ◽  
K. P. M. Heirwegh
Keyword(s):  
Carboxylic Acid ◽  
Rat Liver ◽  
Glucuronic Acid ◽  
Diazonium Salt ◽  
Acid Amide ◽  
Uridine Diphosphate ◽  
Prolonged Incubation ◽  
Carboxylic Acid Groups ◽  
Decreasing Ph

1. In incubation mixtures containing digitonin-activated or untreated preparations from rat liver, albumin-solubilized bilirubin as the acceptor substrate and (a) UDP-glucuronic acid, (b) UDP-glucose or (c) UDP-xylose as the sugar donor, formation of the following ester glycosides was demonstrated: with (a), bilirubin β-d-monoglucuronoside, with (b), bilirubin β-d-monoglucoside and with (c), bilirubin monoxyloside or mixtures of the mono-and di-xyloside. 2. With UDP-glucuronic acid prolonged incubation and variation of the composition of the incubation mixtures yielded equimolar amounts of azodipyrrole (I) and azodipyrrole β-d-monoglucuronoside (II) after treatment of the incubation mixtures with the diazonium salt of ethyl anthranilate. The azo-derivatives were identified by t.l.c. by reference to known compounds and by the following chemical tests. After ammonolysis the conjugated azo-derivative (II) yielded d-glucuronic acid and the carboxylic acid amide of azodipyrrole, indicating transfer of a glucuronic acid residue to the carboxylic acid groups of bilirubin. The β-d-configuration of the sugar moiety and binding at C-1 were demonstrated by enzymic hydrolysis tests. 3. Analogous evidence established the structure of the reaction product obtained with UDP-glucose as the sugar donor, as bilirubin β-d-monoglucoside. 4. With UDP-xylose as the sugar donor xylosyl transfer to the carboxylic acid groups of bilirubin with attachment at C-1 was demonstrated in an analogous way. A β-d-configuration is considered very likely, but requires confirmation. 5. Monoxyloside formation was predominant at pH7.4, whereas at decreasing pH values increasing fractions of the substrate were converted into the dixyloside. Prolonged incubation, low concentrations of bilirubin and high concentrations of UDP-xylose favoured diconjugate formation. The available evidence supports the synthesis sequence: bilirubin → bilirubin monoxyloside → bilirubin dixyloside.

scholarly journals Proteolytic cleavage of haptoglobin occurs in a subcompartment of the endoplasmic reticulum: evidence from membrane fusion in vitro.

1993 ◽  
Vol 123 (2) ◽  
pp. 285-291 ◽  
Author(s):  
M Wassler ◽  
E Fries
Keyword(s):  
Liver Homogenate ◽  
Rat Hepatocytes ◽  
Translation Product ◽  
Alkaline Ph ◽  
Ph Optimum ◽  
Gtp Hydrolysis ◽  
Cytoplasmic Proteins ◽  
Gamma S ◽  
Stimulation Of

The primary translation product of haptoglobin mRNA is a 45-kD polypeptide which is proteolytically cleaved shortly after its synthesis. Previous studies have indicated that the cleavage of this proform of haptoglobin occurs in the ER. In an attempt to characterize the cleaving enzyme, we found that upon incubation of microsomes from rat hepatocytes pulse labeled with [35S]methionine, little cleavage of labeled prohaptoglobin occurred. In contrast, when cells whose cytoplasmic proteins had been released by saponin treatment were incubated, 30-40% of the prohaptoglobin was cleaved. The addition of GTP caused a twofold stimulation, which was abolished by the nonhydrolyzable analog GTP gamma S. With a homogenate of the cells, the addition of GTP resulted in a fourfold stimulation of the degree of cleavage--from 15 to 60%. Differential centrifugation revealed that most of the cleaving activity resided in membranes sedimenting similarly to mitochondria and to a small fraction of the ER. These rapidly sedimenting membranes were therefore prepared from a rat liver homogenate. Upon treatment with high salt, light membranes were released which, when incubated with microsomes of pulse-labeled hepatocytes in the presence of detergent (and in the absence of GTP), induced specific cleavage of prohaptoglobin. The cleaving enzyme had an alkaline pH optimum indicating that it was not of lysosomal origin. These results suggest that cleavage of prohaptoglobin occurs in a subcompartment of the ER. Apparently, the connection between this compartment and the bulk of the ER is broken upon saponin treatment or homogenization but can be reestablished through a process requiring GTP hydrolysis.

scholarly journals A Unique α-1,3 Mannosyltransferase of the Pathogenic Fungus Cryptococcus neoformans

1999 ◽  
Vol 181 (17) ◽  
pp. 5482-5488 ◽  
Author(s):  
Tamara L. Doering
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Drug Discovery ◽  
Cryptococcus Neoformans ◽  
Glucuronic Acid ◽  
Divalent Cations ◽  
Pathogenic Fungus ◽  
Product Formation ◽  
Ph Optimum ◽  
Major Virulence Factor

ABSTRACT The major virulence factor of the pathogenic fungusCryptococcus neoformans is an extensive polysaccharide capsule which surrounds the cell. Almost 90% of the capsule is composed of a partially acetylated linear α-1,3-linked mannan substituted with d-xylose and d-glucuronic acid. A novel mannosyltransferase with specificity appropriate for a role in the synthesis of this glucuronoxylomannan is active in cryptococcal membranes. This membrane-associated activity transfers mannose in vitro from GDP-mannose to an α-1,3-dimannoside acceptor, forming a second α-1,3 linkage. Product formation by the transferase is dependent on protein, time, temperature, divalent cations, and each substrate. It is not affected by amphomycin or tunicamycin but is inhibited by GDP and mannose-1-phosphate. The described activity is not detectable in the model yeast Saccharomyces cerevisiae, consistent with the absence of a similar polysaccharide structure in that organism. A second mannosyltransferase from C. neoformans membranes adds mannose in α-1,2 linkage to the same dimannoside acceptor. The two activities differ in pH optimum and cation preference. While the α-1,2 transferase does not have specificity appropriate for a role in glucuronoxylomannan synthesis, it may participate in production of mannoprotein components of the capsule. This study suggests two new targets for antifungal drug discovery.

scholarly journals The mechanism of biosynthesis and direction of chain extension of a polyl-(N-acetylglucosamine 1-phosphate) from the walls of Staphylococcus lactis N.C.T.C. 2102

1969 ◽  
Vol 113 (4) ◽  
pp. 635-642 ◽  
Author(s):  
D. Brooks ◽  
J Baddiley
Keyword(s):  
Enzyme System ◽  
Group Analysis ◽  
Chain Extension ◽  
Pulse Labelling ◽  
Uridine Diphosphate ◽  
High Concentration ◽  
Ph Optimum ◽  
Enzyme Preparations ◽  
End Group

1. The synthesis of a polymer of N-acetylglucosamine 1-phosphate, occurring in the walls of Staphylococcus lactis N.C.T.C. 2102, was examined by using cell-free enzyme preparations. The enzyme system was particulate, and probably represents fragmented cytoplasmic membrane. 2. Uridine diphosphate N-acetylglucosamine was the only substrate required for polymer synthesis and labelled substrate was used to show that N-acetylglucosamine 1-phosphate is transferred as an intact unit from substrate to polymer. 3. The properties of the enzyme system were studied. A high concentration of Mg2+ or Mn2+ was required for optimum activity, and the pH optimum was about 8·5. 4. End-group analysis during synthesis in vitro showed that newly formed chains contain up to about 15 repeating units. Pulse-labelling indicated that chain extension occurs by transfer from the nucleotide to the ‘sugar-end’ of the chain, i.e. to the end that is not attached to peptidoglycan in the wall.

In Vitro Diabetogenic Effect of Cadmium on Liver

2017 ◽  
Vol 8 (01) ◽  
Author(s):  
Agung Biworo ◽  
Dwi Rezki Amalia ◽  
Gratianus Billy Himawan ◽  
Lisda Rizky Amalia ◽  
Valentina Halim ◽  
...  
Keyword(s):  
Glucose Metabolism ◽  
Liver Homogenate ◽  
Liver Cells ◽  
Male Rats ◽  
Glycogen Level ◽  
Liver Sample ◽  
Km Value ◽  
Cd Exposure ◽  
Menten Constant

The objectives of this study were to determine the effect of cadmium (Cd) on glucose metabolism disruption in liver cells homogenate in vitro. The glucose metabolism disruption was analyzed by measuring the level of liver glucose, glycogen and methylglyoxal (MG), and the activity of glucokinase activity. In this experiment, a liver sample was taken from male rats (Rattus novergicus). Samples then homogenized and divided into four groups with; C served as control which contains liver homogenate only; T1 which contains liver homogenate + 0.03 mg/l of cadmium sulphate (CdSO4); T2 which contains liver homogenate + 0.3 mg/l of CdSO4; and T3 which contains liver homogenate + 3 mg/l of CdSO4. After treatment, liver glucose, glycogen, and MG levels, and glucokinase activity were estimated. The activity of liver glucokinase was estimated by measuring the Michaelis-Menten constant (Km) value. The results revealed that Cd exposure could significantly increase glucose and MG levels, the Km value of glucokinase, and decreased the glycogen level in liver cells (P>0.05). These results indicated that Cd exposure induced the disruption of glucose metabolism in the liver.

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