scholarly journals Enzymic hydrolysis of sphingomyelin by rat liver

1966 ◽  
Vol 98 (3) ◽  
pp. 763-769 ◽  
Author(s):  
M Heller ◽  
B Shapiro
Keyword(s):  
Rat Liver ◽  
Enzymic Hydrolysis ◽  
Hydrolysis Of

scholarly journals Biochemical and cytochemical localization of inosine-5′-diphosphatase in rat liver microsomal fractions

1984 ◽  
Vol 218 (2) ◽  
pp. 501-510 ◽  
Author(s):  
J S Little
Keyword(s):  
Electron Microscope ◽  
Rat Liver ◽  
Incubation Medium ◽  
Microsomal Membrane ◽  
Enzymic Hydrolysis ◽  
Major Fraction ◽  
Cytochemical Localization ◽  
Hydrolysis Of ◽  
Cytoplasmic Side

A procedure has been developed for the biochemical and cytochemical localization of inosine-5′-diphosphatase (IDPase) in rat liver microsomal fractions. The concentration of Pb2+ ions used in the cytochemical incubation medium inhibited IDPase by 32%. IDP formed during the incubation was not hydrolysed further to inosine, and no significant non-enzymic hydrolysis of substrate occurred. When microsomal fractions were incubated cytochemically for IDPase and separated from unchanged substrate under conditions such that the microsomal membrane was not permeable to EDTA, approx. 80% of the reaction product was solubilized by EDTA. In the electron microscope, lead precipitate was observed on the cytoplasmic side (outside) of a major fraction of the vesicles and on the cisternal side (inside) of others. After extraction with EDTA, the lead precipitate was observed only on the cisternal side. Since it was shown that phosphate is trapped on the same side of the membrane as it is released, it is concluded that IDPase can release phosphate on either the cisternal or the cytoplasmic side of the microsomal membrane.

scholarly journals Mechanism of hydroxylation at C-22 during the biosynthesis of ecdysteroids in the locust Schistocerca gregaria

1982 ◽  
Vol 208 (3) ◽  
pp. 857-864 ◽  
Author(s):  
D R Greenwood ◽  
H H Rees
Keyword(s):  
Rat Liver ◽  
Adult Female ◽  
Schistocerca Gregaria ◽  
Mevalonic Acid ◽  
Enzymic Hydrolysis ◽  
Hydrogen Atoms ◽  
Hydrolysis Of

1. The fates of the 22-pro-R and 22-pro-S hydrogen atoms of cholesterol during the biosynthesis of ecdysteroids in the ovaries of Schistocerca gregaria were investigated. 2. Two stereospecifically labelled cholesterol species, obtained by incubating 3R,2R- and 3R,2S-[2-14C, 2-3H]mevalonic acid with rat liver preparations, were administered, in turn, to maturing adult female locusts and the radiolabelled ecdysteroid conjugates isolated from the eggs. Enzymic hydrolysis of the conjugates yielded free ecdysteroids, from which ecdysone was purified. 3. Derivative formation and oxidation at C-22 of both ecdysone samples indicated that the 22-pro-R and 22-pro-S hydrogen atoms of cholesterol were stereospecifically eliminated and retained respectively during ecdysteroid formation. This indicates that C-22 hydroxylation in ecdysone biosynthesis is direct and occurs with retention of configuration.

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

Variation in Quantity of Methanol Recovered from Raisins

1963 ◽  
Vol 46 (2) ◽  
pp. 341-343
Author(s):  
M Alice Brown ◽  
James R Woodward ◽  
Floyd DeEds
Keyword(s):  
Methyl Ester ◽  
Esterase Activity ◽  
Enzymic Hydrolysis ◽  
Methanol Content ◽  
Naturally Occurring ◽  
Pectin Esterase ◽  
Hydrolysis Of

Abstract The amount of naturally occurring methanol in fruit must be known so that the quantity left as fumigation residue can be determined. In a study of methanol content of raisins, which had given inconsistent results, the raisins were subjected to different conditions of treatment immediately prior to methanol determination. Conditions that favored pectin esterase activity gave higher values for methanol content than conditions known to inactivate enzymes. Evidence was also obtained that both chemical and enzymic hydrolysis of methyl ester groups of pectic materials occur during analysis.

scholarly journals Permeability of muscle capillaries to small heme-peptides. Evidence for the existence of patent transendothelial channels.

1975 ◽  
Vol 64 (3) ◽  
pp. 586-607 ◽  
Author(s):  
N Simionescu ◽  
M Siminoescu ◽  
G E Palade
Keyword(s):  
Plasma Proteins ◽  
Intercellular Junctions ◽  
Rat Diaphragm ◽  
Enzymic Hydrolysis ◽  
Graphic Analysis ◽  
Heme Peptides ◽  
Future Work ◽  
Hydrolysis Of ◽  
Muscle Capillaries

Two heme-peptides (HP) of about 20-A diameter (heme-undecapeptide [H11P], mol wt approximately 1900 and heme-octapeptide [H8P], mol wt approximately 1550), obtained by enzymic hydrolysis of cytochrome c, were sued as probe molecules in muscle capillaries (rat diaphragm). They were localized in situ by a perixidase reaction, enhanced by the addition of imidazole to the incubation medium. Chromatography of plasma samples showed that HPs circulate predominantly as monomers for the duration of the experiments and are bound by aldehyde fixatives to plasma proteins to the extent of approximately 50% (H8P) to approximately 95% (H11P). Both tracers cross the endothelium primarily via plasmalemmal vesicles which become progressively labeled (by reaction product) from the blood front to the tissue front of the endothelium, in three successive resolvable phases. By the end of each phase the extent of labeling reaches greater than 90% of the corresponding vesicle population. Labeled vesicles appear as either isolated units or chains which form patent channels across the endothelium. The patency of these channels was checked by specimen tilting and graphic analysis of their images. No evidence was found for early or preferential marking of the intercellular junctions and spaces by reaction product. It is concluded that the channels are the most likely candidate for structural equivalents of the small pores of the capillary wall since they are continuous, water-filled passages, and are provided with one or more strictures of less than 100 A. Their frequency remains to be established by future work.

Investigation of the products of an enzymic hydrolysis of collagens

Biochemistry ◽  
1969 ◽  
Vol 8 (12) ◽  
pp. 4716-4723 ◽  
Author(s):  
Howard B. Bensusan
Keyword(s):  
Enzymic Hydrolysis ◽  
Hydrolysis Of

scholarly journals Constancy of the optimum temperature of an enzyme under varying concentrations of substrate and of enzyme

1914 ◽  
Vol 88 (602) ◽  
pp. 258-262
Keyword(s):  
Experimental Evidence ◽  
Aspergillus Oryzae ◽  
Hydrolytic Enzyme ◽  
Fixed Duration ◽  
Optimum Temperature ◽  
Enzymic Hydrolysis ◽  
Main Interest ◽  
General Law ◽  
The Moment ◽  
Hydrolysis Of

In a recent paper a new enzymic relation is recorded. For the enzymic hydrolysis of salicin—by the enzyme which Gabriel Bertrand and the author have named salicinase —it is found that, in an action of fixed duration, the temperature of greatest activity of the ferment is always the same, whatever the dilutions of substrate and of enzyme adopted for the determination. In other words, the duration of the action being constant, the optimum tem­perature of the ferment is independent of the concentration both of the substrate and of the enzyme. The observation is suggestive: if true of one enzyme it may be true of all, and possibly becomes the enunciation of a general law. Herein, for the moment, lies its main interest. In the present paper further experimental evidence for this hypothesis in given, in the case of another hydrolytic enzyme, the maltase of Aspergillus oryzæ (taka-diastase).

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.

scholarly journals The roles of phospholipase D and a GTP-binding protein in guanosine 5′-[γ-thio]triphosphate-stimulated hydrolysis of phosphatidylcholine in rat liver plasma membranes

1990 ◽  
Vol 272 (3) ◽  
pp. 749-753 ◽  
Author(s):  
K M Hurst ◽  
B P Hughes ◽  
G J Barritt
Keyword(s):  
Rat Liver ◽  
Phospholipase D ◽  
Plasma Membranes ◽  
Regulatory Protein ◽  
Gtp Binding ◽  
Liver Plasma Membranes ◽  
Low Concentrations ◽  
Rat Liver Plasma Membranes ◽  
Triton X ◽  
Hydrolysis Of

1. Guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulated by 50% the rate of release of [3H]choline and [3H]phosphorylcholine in rat liver plasma membranes labelled with [3H]choline. About 70% of the radioactivity released in the presence of GTP[S] was [3H]choline and 30% was [3H]phosphorylcholine. 2. The hydrolysis of phosphorylcholine to choline and the conversion of choline to phosphorylcholine did not contribute to the formation of [3H]choline and [3H]phosphorylcholine respectively. 3. The release of [3H]choline from membranes was inhibited by low concentrations of SDS or Triton X-100. Considerably higher concentrations of the detergents were required to inhibit the release of [3H]phosphorylcholine. 4. Guanosine 5′-[beta gamma-imido]triphosphate and guanosine 5′-[alpha beta-methylene]triphosphate, but not adenosine 5′-[gamma-thio]-triphosphate, stimulated [3H]choline release to the same extent as did GTP[S]. The GTP[S]-stimulated [3H]choline release was inhibited by guanosine 5′-[beta-thio]diphosphate, GDP and GTP but not by GMP. 5. It is concluded that, in rat liver plasma membranes, (a) GTP[S]-stimulated hydrolysis of phosphatidylcholine is catalysed predominantly by phospholipase D with some contribution from phospholipase C, and (b) the stimulation of phosphatidylcholine hydrolysis by GTP[s] occurs via a GTP-binding regulatory protein.

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