scholarly journals Studies of the oestrogen sulphatase and arylsulphatase C activities of rat liver

1972 ◽  
Vol 128 (2) ◽  
pp. 337-345 ◽  
Author(s):  
J. O. Dolly ◽  
K. S. Dodgson ◽  
F. A. Rose
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Competitive Inhibition ◽  
Similar Rate ◽  
Physiological Significance ◽  
Heat Inactivation ◽  
Mixed Substrate ◽  
Oestrone Sulphate ◽  
Foetal Liver ◽  
Hydrolysis Of

Detailed studies on the hydrolysis of p-acetylphenyl sulphate and oestrone sulphate by rat liver preparations strongly indicate that arylsulphatase C and oestrogen sulphatase are the same enzyme. Liver is the richest source of both enzymes, which have identical intracellular distributions, being localized mainly in the microsomal fraction. Low oestrogen sulphatase and arylsulphatase C activities were present in foetal liver and these increased at a similar rate after birth. The activities of the enzymes in an ethionine-induced hepatoma were similarly low. Results of heat inactivation, mixed-substrate and competitive-inhibition experiments employing liver microsomal fractions were also consistent with one enzyme being involved. Oestradiol-17β 3-sulphate was also hydrolysed by microsomal preparations and activity towards both this substrate and oestrone sulphate was inhibited by oestrone and oestradiol-17β. The physiological significance of this inhibition is discussed.

scholarly journals Hydrolysis of membrane phospholipids by phospholipases of rat liver lysosomes

1979 ◽  
Vol 182 (2) ◽  
pp. 599-606 ◽  
Author(s):  
Donald E. Richards ◽  
Robin F. Irvine ◽  
Rex M. C. Dawson
Keyword(s):  
Phospholipase C ◽  
Rat Liver ◽  
Lysosomal Enzymes ◽  
Microsomal Fraction ◽  
Water Soluble ◽  
Membrane Phospholipids ◽  
Liver Lysosomes ◽  
Rat Liver Lysosomes ◽  
Hydrolysis Of

(1) The hydrolysis of 32P- or myo-[2-3H]inositol-labelled rat liver microsomal phospholipids by rat liver lysosomal enzymes has been studied. (2) The relative rates of hydrolysis of phospholipids at pH4.5 are: sphingomyelin>phosphatidylethanolamine>phosphatidylcholine> phosphatidylinositol. (3) The predominant products of phosphatidylcholine and phosphatidylethanolamine hydrolysis are their corresponding lyso-compounds, indicating a slow rate of total deacylation. (4) Ca2+ inhibits the hydrolysis of all phospholipids, though only appreciably at high (>5mm) concentration. The hydrolysis of sphingomyelin is considerably less sensitive to Ca2+ than that of glycerophospholipids. (5) Analysis of the water-soluble products of phosphatidylinositol hydrolysis (by using myo-[3H]inositol-labelled microsomal fraction as a substrate) produced evidence that more than 95% of the product is phosphoinositol, which was derived by direct cleavage from phosphatidylinositol, rather than by hydrolysis of glycerophosphoinositol. (6) This production of phosphoinositol, allied with negligible lysophosphatidylinositol formation and a detectable accumulation of diacylglycerol, indicates that lysosomes hydrolyse membrane phosphatidylinositol almost exclusively in a phospholipase C-like manner. (7) Comparisons are drawn between the hydrolysis by lysosomal enzymes of membrane substrates and that of pure phospholipid substrates, and also the possible role of phosphatidylinositol-specific lysosomal phospholipase C in cellular phosphatidylinositol catabolism is discussed.

scholarly journals The action of phosphatidylinositol-specific phospholipases C on membranes

1976 ◽  
Vol 154 (1) ◽  
pp. 203-208 ◽  
Author(s):  
M G Low ◽  
J B Finean
Keyword(s):  
Phospholipase C ◽  
Rat Liver ◽  
Microsomal Fraction ◽  
Phosphatidyl Inositol ◽  
Detectable Effect ◽  
Erythrocyte Ghosts ◽  
Membrane Phospholipids ◽  
Liver Microsomal Fraction ◽  
Hydrolysis Of ◽  
Low Activity

A phospholipase C prepared from lymphocytes readily hydrolysed pure phosphatidyl-inositol but was relatively ineffective against phosphatidylinositol in erythrocyte “ghosts” and rat liver microsomal fraction and also against sonicated lipid extracts from these membranes. In contrast, a phospholipase C prepared from Staphylcoccus aureus readily hydrolysed phosphatidylinositol in sonicated lipid extracts but had only low activity against purified phosphatidylinositol. Unlike the enzyme from lymphocytes, the S. aureus phospholipase C did not require Ca2+ for its activity and was inhibited by cations. The previously reported specificity of this enzyme was confirmed by our observation of hydrolysis of approx. 75% of the phosphatidylinositol in ox, sheep and cat erythrocyte “ghosts” together with no detectable effect on the major erythrocyte membrane phospholipids. The phosphatidylinositol of rat liver microsomal fraction was hydrolysed only to a maximum of 15%. Some preliminary experiments showed that approx. 60% of the phosphatidylinositol of ox or sheep erythrocytes could be hydrolysed without causing substantial haemolysis.

scholarly journals Differences between microsomal and mitochondrial-matrix palmitoyl-coenzyme A hydrolase, and palmitoyl-l-carnitine hydrolase from rat liver

1979 ◽  
Vol 181 (1) ◽  
pp. 119-125 ◽  
Author(s):  
R K Berge ◽  
B Døssland
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Temperature Stability ◽  
Fatty Acyl ◽  
Mitochondrial Matrix ◽  
Microsomal Enzymes ◽  
Coa Hydrolase ◽  
Hydrolysis Of ◽  
Temperature Optima ◽  
Matrix Enzyme

Palmitoyl-CoA hydrolase (EC 3.1.2.2) and palmitoyl-L-carnitine hydrolase (EC 3.1.1.28) activities from rat liver were investigated. 1. Microsomal and mitochondrial-matrix palmitoyl-CoA hydrolase activities had similar pH and temperature optima, although the activities showed different temperature stability. They were inhibited by Pb2+ and Zn2+. The palmitoyl-CoA hydrolase activities in microsomal fraction and mitochondrial matrix were differently affected by the addition of Mg2+, Ca2+, Co2+, K+ and Na+ to the reaction mixture. ATP, ADP and NAD+ stimulated the microsomal activity and inhibited the mitochondrial-matrix enzyme. The activity of both the microsomal and mitochondrial-matrix hydrolase enzymes was specific for long-chain fatty acyl-CoA esters (C12-C18), with the highest activity for palmitoyl-CoA. The apparent Km for palmitoyl-CoA was 47 microM for the microsomal enzyme and 17 microM for the mitochondrial-matrix enzyme. 2. The palmitoyl-CoA hydrolase and palmitoyl-L-carnitine hydrolase activities of microsomal fraction had similar pH optima and were stimulated by dithiothreitol, but were affected differently by the addition of Pb2+, Mg2+, Ca2+, Mn2+ and cysteine. The two enzymes had different temperature-sensitivities. 3. The data strongly suggest that palmitoyl-CoA hydrolase and palmitoyl-L-carnitine hydrolase are separate microsomal enzymes, and that the hydrolysis of palmitoyl-CoA in the microsomal fraction and mitochondria matrix was catalysed by two different enzymes.

scholarly journals Evidence for the existence of isoenzymes of glycerol phosphate acyltransferase

1979 ◽  
Vol 177 (1) ◽  
pp. 283-288 ◽  
Author(s):  
H G Nimmo
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Thiol Group ◽  
Subcellular Fractionation ◽  
Heat Inactivation ◽  
Mitochondrial Enzyme ◽  
Microsomal Enzyme ◽  
Glycerol Phosphate ◽  
Low Concentrations ◽  
High Concentrations

Subcellular-fractionation studies confirmed previous findings that rat liver glycerol phosphate acyltransferase was located in both mitochondria and the microsomal fraction. Studies of the two activities revealed several differences between them. The mitochondrial enzyme had a lower Km for sn-glycerol 3-phosphate and was more resistant to heat inactivation than was the microsomal enzyme. Some preparations of the mitochondrial enzyme were inhibited by high concentrations of glycerol phosphate. The mitochondrial enzyme was not inactivated by thiol-group reagents, whereas the microsomal enzyme was very rapidly inactivated by these compounds. However, the microsomal enzyme could be specifically protected against this inactivation by low concentrations of palmitoyl-CoA. The results indicate the existence of distinct isoenzymes of glycerol phosphate acyltransferase with different intracellular locations.

INCORPORATION OF IODIDE INTO ORGANIC COMPOUNDS IN THE GUINEA PIG THYROID

1963 ◽  
Vol 43 (1) ◽  
pp. 110-118 ◽  
Author(s):  
R. Ekholm ◽  
T. Zelander ◽  
P.-S. Agrell
Keyword(s):  
Guinea Pig ◽  
Protein Binding ◽  
Organic Compounds ◽  
Guinea Pigs ◽  
Microsomal Fraction ◽  
Thyroid Tissue ◽  
Particulate Fraction ◽  
Supernatant Fraction ◽  
Hydrolysis Of

ABSTRACT Guinea pigs, kept on a iodine-sufficient diet, were injected with Na131I and the thyroids excised from 45 seconds to 5 days later. The thyroid tissue was homogenized and separated into a combined nuclear-mitochondrial-microsomal fraction and a supernatant fraction by centrifugation at 140 000 g for one hour. Protein bound 131iodine (PB131I) and free 131iodide were determined in the fractions and the PB131I was analysed for monoiodotyrosine (MIT), diiodotyrosine (DIT) and thyroxine after hydrolysis of PB131I. As early as only 20 minutes after the Na131I-injection almost 100% of the particulate fraction 131I was protein bound. In the supernatant fraction the protein binding was somewhat less rapid and PB131I values above 90% of total supernatant 131I were not found until 3 hours after the injection. In all experiments the total amount of PB131I was higher in the supernatant than in the corresponding particulate fraction. The ratio between supernatant PB131I and pellet PB131I was lower in experiments up to 3 minutes and from 2 to 5 days than in experiments of 6 minutes to 20 hours. Hydrolysis of PB131I yielded, even in the shortest experiments, both MIT and DIT. The DIT/MIT ratio was lower in the experiments up to 2 hours than in those of 3 hours and over.

scholarly journals Hydrolysis of Retinol Palmitate by Rat Liver

1966 ◽  
Vol 241 (1) ◽  
pp. 57-64 ◽  
Author(s):  
S. Mahadevan ◽  
N.I. Ayyoub ◽  
O.A. Roels
Keyword(s):  
Rat Liver ◽  
Hydrolysis Of

scholarly journals Encapsulated NOLA™ Fit 5500 Lactase—An Economically Beneficial Way to Obtain Lactose-Free Milk at Low Temperature

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 527
Author(s):  
Katarzyna Czyzewska ◽  
Anna Trusek
Keyword(s):  
Low Temperature ◽  
Storage Temperature ◽  
Competitive Inhibition ◽  
Caloric Content ◽  
Substrate Diffusion ◽  
Galactose Inhibition ◽  
The Subject ◽  
And Storage ◽  
Food Processes ◽  
Hydrolysis Of

The current requirements of industrial biocatalysis are related to economically beneficial and environmentally friendly processes. Such a strategy engages low-temperature reactions. The presented approach is essential, especially in food processes, where temperature affects the quality and nutritional value foodstuffs. The subject of the study is the hydrolysis of lactose with the commercial lactase NOLA™ Fit 5500 (NOLA). The complete decomposition of lactose into two monosaccharides gives a sweeter product, recommended for lactose intolerant people and those controlling a product’s caloric content. The hydrolysis reaction was performed at 15 °C, which is related to milk transportation and storage temperature. The enzyme showed activity over the entire range of substrate concentrations (up to 55 g/L lactose). For reusability and easy isolation, the enzyme was encapsulated in a sodium alginate network. Its stability allows carrying out six cycles of the complete hydrolysis of lactose to monosaccharides, lasting from two to four hours. During the study, the kinetic description of native and encapsulated NOLA was conducted. As a result, the model of competitive galactose inhibition and glucose mixed influence (competitive inhibition and activation) was proposed. The capsule size does not influence the reaction rate; thus, the substrate diffusion into capsules can be omitted from the process description. The prepared 4 mm capsules are easy to separate between cycles, e.g., using sieves.

Influence of 1,4-benzdiazepin-2-ones on rat liver microsomal fraction and hepatocytes

1987 ◽  
Vol 21 (1) ◽  
pp. 5-8
Author(s):  
T. I. Davidenko ◽  
O. V. Sevast'yanov ◽  
L. N. Yakubovskaya
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Liver Microsomal Fraction

scholarly journals Loss of haem in rat liver caused by the porphyrogenic agent 2-allyl-2-isopropylacetamide

1971 ◽  
Vol 124 (4) ◽  
pp. 767-777 ◽  
Author(s):  
F. De Matteis
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Direct Evidence ◽  
Gradual Increase ◽  
Rapid Loss ◽  
Metabolizing Enzymes ◽  
Liver Microsomal Fraction ◽  
Green Pigments ◽  
Cytochrome P 450 ◽  
Increased Activity

1. The effect of a single dose of 2-allyl-2-isopropylacetamide on the cytochrome P-450 concentration in rat liver microsomal fraction was studied. The drug caused a rapid loss of cytochrome P-450 followed by a gradual increase to above the normal concentration. 2. The loss of cytochrome P-450 was accompanied by a loss of microsomal haem and by a brown–green discoloration of the microsomal fraction suggesting that a change in the chemical constitution of the lost haem had taken place. Direct evidence for this was obtained by prelabelling the liver haems with radioactive 5-aminolaevulate: the drug caused a loss of radioactivity from the haem with an increase of radioactivity in a fraction containing certain un-identified green pigments. 3. Evidence was obtained by a dual-isotopic procedure that rapidly turning-over haem(s) may be preferentially affected. 4. The loss of cytochrome P-450 as well as the loss of microsomal haem and the discoloration of the microsomal fraction were more intense in animals pretreated with phenobarbitone and were much less evident when compound SKF 525-A (2-diethylaminoethyl 3,3-diphenylpropylacetate) was given before 2-allyl-2-isopropylacetamide, suggesting that the activity of the drug-metabolizing enzymes may be involved in these effects. 5. The relevance of the destruction of liver haem to the increased activity of 5-aminolaevulate synthetase caused by 2-allyl-2-isopropylacetamide is discussed.

scholarly journals Chain extension of ribonucleic acid by enzymes from rat liver cytoplasm

1968 ◽  
Vol 109 (4) ◽  
pp. 485-494 ◽  
Author(s):  
N. M. Wilkie ◽  
R. M. S. Smellie
Keyword(s):  
Rat Liver ◽  
Alkaline Hydrolysis ◽  
Actinomycin D ◽  
Chain Extension ◽  
Supernatant Fraction ◽  
Inorganic Pyrophosphate ◽  
Optimum Ph ◽  
Microsome Fraction ◽  
Hydrolysis Of ◽  
Generating System

1. The 105000g supernatant fraction of rat liver catalyses the incorporation of ribonucleotides from ribonucleoside triphosphates into polyribonucleotide material. The reaction requires Mg2+ ions and is enhanced by the addition of an ATP-generating system and RNA, ATP, UTP and CTP but not GTP are utilized in this reaction. In the case of UTP, the product is predominantly a homopolymer containing 2–3 uridine residues, and there is evidence that these may be added to the 3′-hydroxyl ends of RNA or oligoribonucleotide primers. 2. The microsome fraction of rat liver incorporates ribonucleotides from ATP, GTP, CTP and UTP into polyribonucleotide material. This reaction requires Mg2+ ions and is enhanced slightly by the addition of an ATP-generating system, and by RNA but not DNA. Supplementation of the reaction mixture with the three complementary ribonucleoside 5′-triphosphates greatly increases the utilization of a single labelled ribonucleoside 5′-triphosphate. The optimum pH is in the range 7·0–8·5, and the reaction is strongly inhibited by inorganic pyrophosphate and to a much smaller degree by inorganic orthophosphate. It is not inhibited by actinomycin D or by deoxyribonuclease. In experiments with [32P]UTP in the absence of ATP, GTP and CTP, 80–90% of 32P was recovered in UMP-2′ or −3′ after alkaline hydrolysis of the reaction product. When the reaction mixture was supplemented with ATP, GTP and CTP, however, about 40% of the 32P was recovered in nucleotides other than UMP-2′ or −3′. Although the reactions seem to lead predominantly to the synthesis of homopolymers, the possibility of some formation of some heteropolymer is not completely excluded.

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