scholarly journals Species differences in the conjugation of 4-hydroxy-3-methoxyphenylethanol with glucuronic acid and sulphuric acid

1976 ◽  
Vol 158 (1) ◽  
pp. 33-37 ◽  
Author(s):  
K P Wong
Keyword(s):  
Human Liver ◽  
High Speed ◽  
Species Differences ◽  
Glucuronic Acid ◽  
Mitochondrial Fraction ◽  
Mouse Kidney ◽  
Enzyme Preparations ◽  
Guinea Pig Liver ◽  
High Speed Supernatant

The biosynthesis of the glucuronide and sulphate conjugates of 4-hydroxy-3-methoxyphenylethanol was demonstrated in vitro by using the high-speed supernatant and microsomal fractions of liver respectively. These two conjugates were also produced simultaneously by using the post-mitochondrial fraction of rat, rabbit or guinea-pig liver. In contrast only the glucuronide was synthesized by human liver and only the sulphate by mouse and cat livers. Neither of these conjugates was formed by the kidney or the small or large intestine of the rat. A high sulphate-conjugating activity was observed in mouse kidney; the rate of sulphation of 4-hydroxy-3-methoxyphenylethanol with kidney homogenate and high-speed supernatant preparations was 1.8 times greater than with liver preparations. The sulpho-conjugates of 4-hydroxy-3-methoxyphenylethanol and 4-hydroxy-3-methoxy-phenylglycol were also formed by enzyme preparations of rabbit adrenal and rat brain; the glycol was the better substrate in the latter system. Mouse brain did not possess any sulphotransferase activity. For the conjugation of 4-hydroxy-3-methoxyphenylethanol by rabbit liver, the Km for UDP-glucuronic acid was 0.22 mM and that for Na2SO4 was 3.45 mM. The sulphotransferase has a greater affinity for 4-hydroxy-3-methoxyphenyl-ethanol than has glucuronyltransferase, as indicated by their respective Km values of 0.036 and 1.3 mM. It was concluded that sulphate conjugation of 4-hydroxy-3-methoxyphenylethanol predominates in most species of animals.

Reduction of 7-ketolithocholic acid by human liver enzyme preparations in vitro

1989 ◽  
Vol 256 (1) ◽  
pp. G67-G71
Author(s):  
Y. Amuro ◽  
W. Yamade ◽  
K. Kudo ◽  
T. Yamamoto ◽  
T. Hada ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Liver Enzyme ◽  
Chenodeoxycholic Acid ◽  
Human Liver ◽  
Potassium Phosphate ◽  
Gas Chromatography Mass Spectrometry ◽  
Potassium Phosphate Buffer ◽  
Sodium Potassium ◽  
Enzyme Preparations

The formation of chenodeoxycholic and ursodeoxycholic acids from 7-ketolithocholic acid by human liver preparations was examined in vitro. Liver preparations were incubated with 7-ketolithocholic acid at pH 5.5 in a sodium-potassium-phosphate buffer containing NADPH or NADH. The products formed were analyzed by gas chromatography and gas chromatography-mass spectrometry. Results showed that chenodeoxycholic and ursodeoxycholic acids could be formed from 7-ketolithocholic acid by human liver enzyme(s). The enzyme(s) required NADPH but not NADH as coenzyme and was localized largely in the microsomes. The conjugated 7-ketolithocholic acid, especially the taurine conjugated, was predominantly reduced to chenodeoxycholic acid, whereas the unconjugated 7-ketolithocholic acid was not reduced well to either chenodeoxycholic acid or ursodeoxycholic acid. Thus the reduction of 7-ketolithocholic acid by human liver enzyme(s) was found to be dependent on whether the substrate was conjugated or not.

scholarly journals Studies on the meta and para O-sulphation of the catechol compound 3,4-dihydroxybenzoic acid by rat liver sulphotransferase in vitro

1980 ◽  
Vol 191 (1) ◽  
pp. 133-138 ◽  
Author(s):  
E J M Pennings ◽  
G M J Van Kempen
Keyword(s):  
Chemical Synthesis ◽  
Rat Liver ◽  
High Speed ◽  
Helix Pomatia ◽  
Dihydroxybenzoic Acid ◽  
High Speed Supernatant ◽  
Optimal Ph

The enzymic meta and para O-sulphation of 3,4-dihydroxybenzoic acid was investigated in vitro with a dialysed high-speed supernatant from rat liver. The O-sulphated products were identified by comparison with the reference compounds. The chemical synthesis and identification of the reference O-sulphate esters is described in detail. The sulphotransferase activity of the dialysed supernatant from rat liver towards 3,4-dihydroxybenzoic acid was 580 pmol of 3-O-sulphate and 120 pmol of 4-O-sulphate formed/min per mg of protein at the optimal pH of 7.4. The meta/para ratio of O-sulphation was independent of pH, time of incubation, concentration of enzyme and presence of dithiothreitol. The O-sulphate esters of 3,4-dihydroxybenzoic acid were found to be good substrates for the arylsulphatase reaction at pH 5.6. The arylsulphatase activity of a dialysed preparation from rat liver was 4.0 nmol of 3-O- and 5.7 nmol of 4-O-sulphate ester hydrolysed/min per mg of protein, respectively. Arylsulphatase from Helix pomatia had an activity of 620 pmol of 3-O-sulphate and of 16.6 nmol of 4-O-sulphate ester hydrolysed/min per unit (mumol/h) of sulphatase.

scholarly journals BRAIN MITOCHONDRIA

1963 ◽  
Vol 19 (2) ◽  
pp. 309-316 ◽  
Author(s):  
Diana S. Beattie ◽  
Howard R. Sloan ◽  
R. E. Basford
Keyword(s):  
High Speed ◽  
Brain Cortex ◽  
Lactate Production ◽  
Mitochondrial Fraction ◽  
Brain Mitochondria ◽  
Glycolytic Enzymes ◽  
Supernatant Fraction ◽  
Glycolytic Activity ◽  
High Speed Supernatant ◽  
Stimulation Of

A mitochondrial fraction prepared from calf brain cortex possessed negligible glycolytic activity in the absence of the enzymes of the high speed supernatant fraction. When mitochondria were added to a supernatant system supplemented with optimal amounts of crystalline hexokinase, a 20 per cent stimulation of glycolysis was observed. The supernatant fraction produced minimal amounts of lactate in the absence of exogenous hexokinase; the addition of mitochondria doubled the lactate production. The substitution of glycolytic intermediates for glucose as substrates as well as the addition of exogenous glycolytic enzymes to the supernatant fraction or supernatant fraction plus mitochondria indicated that the mitochondria contributed mainly hexokinase and phosphofructokinase. By direct assay of all of the enzymes of the glycolytic pathway, only hexokinase and phosphofructokinase were shown to be concentrated in the mitochondrial fraction. All other glycolytic enzymes were found to exhibit higher total and specific activities in the supernatant fraction.

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.

Serotonin (5-hydroxytryptamine) glucuronidation in vitro : assay development, human liver microsome activities and species differences

Xenobiotica ◽  
2003 ◽  
Vol 33 (2) ◽  
pp. 169-180 ◽  
Author(s):  
S. Krishnaswamy ◽  
S. X. Duan ◽  
L. L. Von Moltke ◽  
D. J. Greenblatt ◽  
J. L. Sudmeier ◽  
...  
Keyword(s):  
Human Liver ◽  
Species Differences ◽  
Liver Microsome ◽  
Human Liver Microsome ◽  
In Vitro Assay ◽  
Assay Development ◽  
Vitro Assay

scholarly journals Measurement and kinetic study of the formation of adrenaline sulphate in vitro

1978 ◽  
Vol 174 (3) ◽  
pp. 777-782 ◽  
Author(s):  
K P Wong
Keyword(s):  
Small Intestine ◽  
Guinea Pig ◽  
High Speed ◽  
Maximal Activity ◽  
Ph Optimum ◽  
Inorganic Sulphate ◽  
Measurable Activity ◽  
Small Intestines ◽  
High Speed Supernatant

The sulpho-conjugation of [14C]adrenaline form inorganic sulphate and ATP or preformed adenosine 3′-phosphate 5′-sulphatophosphate was demonstrated in the high-speed supernatant prepared from the liver and small intestine of various animals. Hydrolysis with sulphatase indicated the sulphate nature of the conjugate. The overall sulphation reaction has a pH optimum of 9.0. Maximal activity was obtained with a ratio of ATP/Mg2+ of 1 at 4–6mM. Above their optimal concentrations, ATP and Mg2+, separately or in combination, were inhibitory. Dithiothreitol at 3 mM stimulated the reaction by about 30%. The Km for adrenaline, determined by the sulphotransferase reaction and by the three-step (sulphate-activating and sulphotransferase) reactions was 125 micrometer. The rate of synthesis of [14C]-adrenaline sulphate, expressed in pmol/min per mg of protein for the livers of dog, monkey, rat, guinea pig and rabbit were, respectively, 144, 77, 47, 11 and 6. The corresponding values for the small intestines of dog and monkey were 60 and 62. Brain and heart tissues showed no measurable activity.

scholarly journals Metabolism of the herbicide 2,6-dichlorobenzonitrile in rabbits and rats

1966 ◽  
Vol 101 (3) ◽  
pp. 698-706 ◽  
Author(s):  
JG Wit ◽  
H Van Genderen
Keyword(s):  
Oral Administration ◽  
Urinary Excretion ◽  
Rat Liver ◽  
High Speed ◽  
Liver Homogenate ◽  
Acid Formation ◽  
Thiol Compounds ◽  
Enzyme Preparations ◽  
Phenolic Metabolites ◽  
High Speed Supernatant

1. The metabolism of 2,6-dichlorobenzonitrile was studied in rabbits and rats. Oral administration caused an increased urinary excretion of glucuronides and ethereal sulphates. There was also an indication of mercapturic acid formation. 2,6-Dichloro-3-hydroxybenzonitrile and its 4-hydroxy analogue were identified as metabolites in the urine. A small amount of the unchanged substance was recovered from the faeces. 2. By using 2,6-dichlorobenzo[(14)C]nitrile the phenolic metabolites were determined quantitatively and some other possible metabolic routes were excluded. 3. Incubation of 2,6-dichlorobenzonitrile with enzyme preparations (papain and high-speed supernatant of rat-liver homogenate plus glutathione) gave no indications for a reaction with thiol compounds.

scholarly journals Acetylation of serotonin in vitro by a human N-acetyltransferase

1969 ◽  
Vol 113 (4) ◽  
pp. 721-725 ◽  
Author(s):  
Thomas A. White ◽  
John W. Jenne ◽  
David A. Price Evans
Keyword(s):  
Genetic Polymorphism ◽  
Liver Enzyme ◽  
Human Liver ◽  
Natural Substrate ◽  
Enzyme Preparations ◽  
Wide Variability ◽  
Human Livers

1. There is a well-recognized genetic polymorphism for the N-acetylation of isoniazid and sulphamethazine by human livers. 2. Serotonin was found to be acetylated by human liver enzyme preparations and the N-acetylserotonin formed was identified and determined quantitatively. 3. In 13 livers examined there was a wide variability in the capacity to acetylate serotonin that did not correlate with the capacity of the same livers to acetylate isoniazid and sulphamethazine. The results suggest that serotonin is not a natural substrate for the polymorphic N-acetyltransferase and that it may be acetylated by a different enzyme.

Sign in / Sign up

Export Citation Format

Share Document