scholarly journals Vitamin A metabolism in chick liver: some properties of the cytosolic lipid–protein aggregate

1984 ◽  
Vol 52 (1) ◽  
pp. 107-114 ◽  
Author(s):  
D. Sklan ◽  
Orna Halevy
Keyword(s):  
Molecular Weight ◽  
Retinoic Acid ◽  
Alcohol Dehydrogenase ◽  
Glucuronic Acid ◽  
Uridine Diphosphate ◽  
Protein Aggregate ◽  
Vitamin A Metabolism ◽  
Cleavage Activity ◽  
Hepatic Microsomes ◽  
Retinyl Esters

1. Incubation of hepatic microsomes with retinol resulted in formation of retinyl esters and glucuronides. The presence of the cytosolic lipid-protein aggregate (LPA) in the system in addition induced release of holoretinol-binding protein from the microsomes. The extent of these reactions was influenced by the addition of coenzyme A and ATP, or uridine diphosphate glucuronic acid.2. Incubation of hepatic microsomes containing labelled retinyl esters with the LPA resulted in the appearance of the labelled retinyl esters in the LPA.3. Small amounts of retinoic acid were formed on incubation of retinol with microsomes (approximately 1% of added retinol); this was found to be associated with a protein of approximately 14500 molecular weight, and less than 10% was associated with the LPA. This is in contrast to retinol, which was found to be almost completely associated with the LPA.4. The cytosolic LPA was associated both with carotene-cleavage activity and alcohol dehydrogenase (NAD(P)+) (EC 1. 1. 1. 71) activity.5. These findings lend some support to the concept of a specific role for hepatic LPA.

scholarly journals Opposing actions of cellular retinol-binding protein and alcohol dehydrogenase control the balance between retinol storage and degradation

2004 ◽  
Vol 383 (2) ◽  
pp. 295-302 ◽  
Author(s):  
Andrei MOLOTKOV ◽  
Norbert B. GHYSELINCK ◽  
Pierre CHAMBON ◽  
Gregg DUESTER
Keyword(s):  
Retinoic Acid ◽  
Vitamin A ◽  
Alcohol Dehydrogenase ◽  
Retinol Binding Protein ◽  
Dietary Vitamin ◽  
Gene Encoding ◽  
Retinyl Ester ◽  
Ester Formation ◽  
Retinyl Esters ◽  
Cellular Retinol Binding Protein

Vitamin A homoeostasis requires the gene encoding cellular retinol-binding protein-1 (Crbp1) which stimulates conversion of retinol into retinyl esters that serve as a storage form of vitamin A. The gene encoding alcohol dehydrogenase-1 (Adh1) greatly facilitates degradative metabolism of excess retinol into retinoic acid to protect against toxic effects of high dietary vitamin A. Crbp1−/−/Adh1−/− double mutant mice were generated to explore whether the stimulatory effect of CRBP1 on retinyl ester formation is due to limitation of retinol oxidation by ADH1, and whether ADH1 limits retinyl ester formation by opposing CRBP1. Compared with wild-type mice, liver retinyl ester levels were greatly reduced in Crbp1−/− mice, but Adh1−/− mice exhibited a significant increase in liver retinyl esters. Importantly, relatively normal liver retinyl ester levels were restored in Crbp1−/−/Adh1−/− mice. During vitamin A deficiency, the additional loss of Adh1 completely prevented the excessive loss of liver retinyl esters observed in Crbp1−/− mice for the first 5 weeks of deficiency and greatly minimized this loss for up to 13 weeks. Crbp1−/− mice also exhibited increased metabolism of a dose of retinol into retinoic acid, and this increased metabolism was not observed in Crbp1−/−/Adh1−/− mice. Our findings suggest that opposing actions of CRBP1 and ADH1 enable a large fraction of liver retinol to remain esterified due to CRBP1 action, while continuously allowing some retinol to be oxidized to retinoic acid by ADH1 for degradative retinoid turnover under any dietary vitamin A conditions.

Carotene-cleavage activity in chick intestinal mucosa cytosol: association with a high-molecular-weight lipid-protein aggregate fraction and partial characterization of the activity

1983 ◽  
Vol 50 (2) ◽  
pp. 417-425 ◽  
Author(s):  
David Sklan
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Intestinal Mucosa ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Low Molecular Weight ◽  
Protein Aggregate ◽  
Aggregate Fraction ◽  
Cleavage Activity ◽  
Copper Zinc

1. A fluorescent high-molecular weight lipid–protein aggregate was isolated from the cytosol of chick intestinal mucosa or liver by gel filtration on columns of Sepharose 4B or 6B.2. This aggregate exhibited carotene-cleavage activity.3. On incubation of this aggregate, dissociation occurred and low-molecular weight fractions containing Cu and Zn and exhibiting carotene-cleavage activity were found. This fraction appeared on sodium dodecyl sulphate polyacrylamide electrophoresis to have a molecular weight of 7000–11000 and resembled the previously described Cu chelatins in amino acid composition.4. Carotene cleavage may be effected by a copper–zinc metalloprotein of low-molecular weight, associated in intestinal cytosol with a lipid–protein aggregate.

scholarly journals Rat liver alcohol dehydrogenase. Purification and properties

1971 ◽  
Vol 125 (4) ◽  
pp. 1039-1047 ◽  
Author(s):  
M J Arslanian ◽  
E Pascoe ◽  
J G Reinhold
Keyword(s):  
Molecular Weight ◽  
Alcohol Dehydrogenase ◽  
Rat Liver ◽  
Gel Filtration ◽  
Rabbit Antiserum ◽  
Minor Component ◽  
Disc Electrophoresis ◽  
Supernatant Fraction ◽  
Liver Alcohol Dehydrogenase ◽  
A Minor

Alcohol dehydrogenase (EC 1.1.1.1) from the rat liver supernatant fraction has been purified 200-fold and partially characterized. The isolation procedure involved ammonium sulphate fractionation, DEAE-Sephadex chromatography and gel filtration. The purified enzyme behaved as a homogeneous preparation as evaluated by cellulose acetate and polyacrylamide-gel disc electrophoresis. Sulphoethyl-Sephadex chromatography and immunoelectrophoresis with rabbit antiserum indicated the presence of a minor component. Rat liver alcohol dehydrogenase appears to contain 4mol of zinc/mol, has an estimated molecular weight of 65000 and consists of two subunits of similar molecular weight. Heavy-metal ions, thiol-blocking reagents, urea at concentrations below 8m, low pH (5.5) and chelating agents deactivate the enzyme but do not dissociate it into subunits. Deactivated enzyme could not be reactivated. The enzyme is strictly specific for NAD+ and has a broad specificity for alcohols, which are bound at a hydrophobic site. Inhibition occurred with the enzyme equilibrated with Zn2+ at concentrations above 0.1mm.

scholarly journals Enzymic transfer of glucose and xylose from uridine diphosphate glucose and uridine diphosphate xylose to bilirubin by untreated and digitonin-activated preparations from rat liver

1972 ◽  
Vol 129 (3) ◽  
pp. 619-633 ◽  
Author(s):  
J. Fevery ◽  
P. Leroy ◽  
K. P. M. Heirwegh
Keyword(s):  
Enzyme Activities ◽  
Metal Ion ◽  
Glucuronic Acid ◽  
Uridine Diphosphate ◽  
No Formation ◽  
Cell Extracts ◽  
Straight Line ◽  
Standard Assay ◽  
Diphosphate Glucose ◽  
Liver Homogenates

1. Digitonin-treated and untreated homogenates, cell extracts and washed microsomal preparations from liver of Wistar R rats are capable of transferring sugar from UDP-glucose or UDP-xylose to bilirubin. No formation of bilirubin glycosides occurred with UDP-galactose or d-glucose, d-xylose or d-glucuronic acid as the sources of sugar. 2. Procedures to assay digitonin-activated and unactivated bilirubin UDP-glucosyltransferase and bilirubin UDP-xylosyltransferase were developed. 3. In digitonin-activated microsomal preparations the transferring enzymes had the following properties. Both enzyme activities were increased 2.5-fold by pretreatment with digitonin. They were optimum at pH6.6–7.2. Michaelis–Menten kinetics were followed with respect to UDP-glucose. In contrast, double-reciprocal plots of enzyme activity against the concentration of UDP-xylose showed two intersecting straight-line sections corresponding to concentration ranges where either bilirubin monoxyloside was formed (at low UDP-xylose concentrations) or where mixtures of both the mono- and di-xyloside were synthesized (at high UDP-xylose concentrations). Both enzyme activities were stimulated by Mg2+; Ca2+ was slightly less, and Mn2+ slightly more, stimulatory than Mg2+. Of the activities found in standard assay systems containing Mg2+, 58–78% (substrate UDP-glucose) and 0–38% (substrate UDP-xylose) were independent of added bivalent metal ion. Double-reciprocal plots of the Mg2+-dependent activities against the concentration of added Mg2+ were linear. 4. In comparative experiments the relative activities of liver homogenates obtained with UDP-glucuronic acid, UDP-glucose and UDP-xylose were 1:1.5:2.7 for untreated preparations and 1:0.29:0.44 after activation with digitonin. 5. Bilirubin UDP-glucuronyltransferase was protected against denaturation by human serum albumin, whereas bilirubin UDP-xylosyltransferase was not. 6. Digitonin-treated and untreated liver homogenates from Gunn rats were inactive in transferring sugar to bilirubin from UDP-glucuronic acid (in agreement with the work of others), UDP-glucose or UDP-xylose.

Uridine diphosphate β-glucuronic acid. A new substrate for β-glucuronidase

1970 ◽  
Vol 201 (2) ◽  
pp. 375-377 ◽  
Author(s):  
Indrajit Das ◽  
Mark A. Wentworth ◽  
Hiroyuki Ide ◽  
Hsien Gieh Sie ◽  
William H. Fishman
Keyword(s):  
Glucuronic Acid ◽  
Uridine Diphosphate

scholarly journals Normalization of enzyme expression and activity regulating vitamin A metabolism increases RAR-beta expression and reduces cellular migration and proliferation in diseases caused by tuberous sclerosis gene mutations

2020 ◽  
Author(s):  
ElHusseiny MM Abdelwahab ◽  
Judit Bovari-Biri ◽  
Gabor Smuk ◽  
Tunde Harko ◽  
Janos Fillinger ◽  
...  
Keyword(s):  
Cell Migration ◽  
Retinoic Acid ◽  
Vitamin A ◽  
Tuberous Sclerosis ◽  
Cell Lines ◽  
Cellular Proliferation ◽  
Cellular Migration ◽  
Immunofluorescent Staining ◽  
Vitamin A Metabolism ◽  
Expression And Activity

Abstract Background Mutation in a tuberous sclerosis gene (TSC1 or 2) leads to continuous activation of the mammalian target of rapamycin (mTOR). mTOR activation alters cellular including vitamin A metabolism and retinoic acid receptor beta (RARβ) expression. The goal of the present study was to investigate the molecular connection between vitamin A metabolism and TSC mutation. We also aimed to investigate the effect of the FDA approved drug rapamycin and the vitamin A metabolite retinoic acid (RA) in cell lines with TSC mutation. Methods Expression and activity of vitamin A associated metabolic enzymes and RARβ were assessed in human kidney angiomyolipoma derived cell lines, primary lymphangioleiomyomatosis (LAM) tissue derived LAM cell lines as well as RARβ protein levels were tested in primary LAM lung tissue sections. TaqMan arrays, enzyme activities, qRT-PCRs, immunohistochemistry, immunofluorescent staining and western blotting were performed and analysed. The functional effects of retinoic acid (RA) and rapamycin were tested in a scratch and a BrDU assay to assess cell migration and proliferation. Results Metabolic enzyme arrays revealed a general deregulation of many enzymes involved in vitamin A metabolism including aldehyde dehydrogenases (ALDHs), alcohol dehydrogenases (ADHs) and Cytochrome P450 2E1 (CYP2E1). Furthermore, RARβ downregulation was a characteristic feature of all TSC-deficient cell lines and primary tissues. Combination of the two FDA approved drugs -RA for acute myeloid leukaemia and rapamycin for TSC mutation- normalised ALDH and ADH expression and activity, restored RARβ expression and reduced cellular proliferation and migration. Conclusion Deregulation of vitamin A metabolizing enzymes is a feature of TSC mutation. RA can normalize RARβ levels and limit cell migration, but does not have a significant effect on proliferation. Based on our data, translational studies could confirm whether combination of RA with reduced dosage of rapamycin would have more beneficial effects to higher dosage of rapamycin monotherapy meanwhile reducing adverse effects of rapamycin for patients with TSC mutation.

scholarly journals A new bacterial alcohol dehydrogenase active on degraded lignin and several low molecular weight aromatic compounds

1989 ◽  
Vol 57 (1) ◽  
pp. 109-114 ◽  
Author(s):  
Jean Pelmont ◽  
Catherine Tournesac ◽  
Ahmed Mliki ◽  
Michel Barrelle ◽  
Claude Beguin
Keyword(s):  
Molecular Weight ◽  
Alcohol Dehydrogenase ◽  
Aromatic Compounds ◽  
Low Molecular Weight
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