STUDIES ON THE ENZYMIC FORMATION OF DI-IODOTYROSINE BY A MICROSOMAL PREPARATION OF GOAT SUBMAXILLARY GLAND

1969 ◽  
Vol 44 (2) ◽  
pp. 177-185 ◽  
Author(s):  
RATHA N. HATI ◽  
ASOKE G. DATTA
Keyword(s):  
Hydrogen Peroxide ◽  
Microsomal Fraction ◽  
Submaxillary Gland ◽  
Maximum Activity ◽  
Enzymic Activity ◽  
Subcellular Fractions ◽  
Ferric Ions ◽  
Microsomal Preparation

SUMMARY Subcellular fractions of goat submaxillary gland catalysed the iodination of monoiodotyrosine to form di-iodotyrosine; the microsomal fraction was found to have maximum activity. The enzyme needed copper or hydrogen peroxide for its activity. Thiourea and thiouracil inhibited the enzymic activity. Manganese and ferric ions inhibited the enzymic formation of di-iodotyrosine. The enzyme was solubilized by sodium desoxycholate treatment.

scholarly journals Sialyltransferase activity in regenerating rat liver

1977 ◽  
Vol 166 (3) ◽  
pp. 381-386 ◽  
Author(s):  
Franca Serafini-Cessi
Keyword(s):  
Sialic Acid ◽  
Partial Hepatectomy ◽  
Microsomal Fraction ◽  
Incubation Temperature ◽  
Submaxillary Gland ◽  
Sham Operation ◽  
Regenerating Liver ◽  
Microsomal Preparation ◽  
Sialyltransferase Activity ◽  
Triton X

Liver microsomal fractions catalyse the transfer of sialic acid from CMP-N-acetyl-neuraminic acid to various exogenous acceptors such as desialylated fetuin, desialylated human Tamm–Horsfall glycoprotein and desialylated bovine submaxillary-gland mucin. An increase in the rate of incorporation of sialic acid into desialylated glycoproteins was found after a lag period (7h) in regenerating liver. The increase was maximum 24h after partial hepatectomy for all acceptors tested. At later times after operation the sialyltransferase activity remained high only for desialylated fetuin. No soluble factors from liver or serum of partially hepatectomized animals influenced the activity of the sialyltransferases bound to the microsomal fraction. The sensitivity of sialyltransferases to activation by Triton X-100, added to the incubation medium, was unchanged in the microsomal preparation from animals 24h after sham operation or partial hepatectomy. The full activity of sialyltransferases towards the various desialylated acceptors showed some differences. Human Tamm–Horsfall glycoprotein was a good acceptor of sialic acid only when desialylated by mild acid hydrolysis. After this treatment, but not after enzymic hydrolysis, a decrease in molecular weight of human Tamm–Horsfall glycoprotein was observed. Further, the sialyltransferase activity as a function of incubation temperature gave different curves according to the acceptor used. The relationship between the biosynthesis of glycoproteins by regenerating liver and the sialyltransferase activity of microsomal fraction after partial hepatectomy is discussed.

METABOLISM OF PROGESTERONE BY THE RAT OVARY: FORMATION OF 3β-HYDROXY-5α-PREGNAN-20-ONE BY OVARIAN MICROSOMES

1969 ◽  
Vol 61 (4) ◽  
pp. 618-628 ◽  
Author(s):  
A. Zmigrod ◽  
H. R. Lindner
Keyword(s):  
Oxidation Product ◽  
Microsomal Fraction ◽  
Biological Function ◽  
Specific Activity ◽  
Metabolite Identification ◽  
Enzymic Activity ◽  
Chromatographic Behaviour ◽  
Rat Ovary ◽  
Chromatographic Characterization

ABSTRACT A microsomal fraction from rat ovaries incubated with [4-14C] progesterone in the presence of NADPH produced radioactive 3β-hydroxy-5α-pregnan-20-one as the major metabolite. Identification of this compound, not hitherto isolated from mammalian ovaries, was based on (i) paper and gas-chromatographic behaviour of the free compound and its acetate, (ii) gas-chromatographic characterization of the thioketal derivative and the oxidation product, and (iii) recrystallization with authentic carrier to constant specific activity. Ovaries from both pregnant and prooestrous rats showed this enzymic activity. The possible biological function of ovarian steroid reductases is discussed.

Reactions of ferrous and ferric ions with hydrogen peroxide. Part II.—The ferric ion reaction

1951 ◽  
Vol 47 (0) ◽  
pp. 591-616 ◽  
Author(s):  
W. G. Barb ◽  
J. H. Baxendale ◽  
P. George ◽  
K. R. Hargrave
Keyword(s):  
Hydrogen Peroxide ◽  
Ferric Ion ◽  
Ferric Ions

scholarly journals 3-Hydroxy-3-methylglutaryl-coenzyme A reductase. A comparison of the modulation in vitro by phosphorylation and dephosphorylation to modulation of enzyme activity by feeding cholesterol- or cholestyramine-supplemented diets

1980 ◽  
Vol 185 (2) ◽  
pp. 435-441 ◽  
Author(s):  
Konstantinos A. Mitropoulos ◽  
Brian L. Knight ◽  
Bernard E. A. Reeves
Keyword(s):  
Microsomal Fraction ◽  
Coenzyme A ◽  
Maximal Activity ◽  
Kinetic Properties ◽  
Standard Diet ◽  
Microsomal Preparation ◽  
Phosphoprotein Phosphatase ◽  
Coa Reductase ◽  
Hydroxymethylglutaryl Coa Reductase ◽  
Coenzyme A Reductase

The activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hydroxymethylglutaryl-CoA reductase) was considerably inhibited during incubation with ATP+Mg2+. The inactivated enzyme was reactivated on further incubation with partially purified cytosolic phosphoprotein phosphatase. The inactivation was associated with a decrease in the apparent Km of the reductase for hydroxymethylglutaryl-CoA, and this was reversed on reactivation. The slight increase in activity observed during incubation of microsomal fraction without ATP was not associated with a change in apparent Km and, unlike the effect of the phosphatase, was not inhibited by NaF. Liver microsomal fraction from rats given cholesterol exhibited a low activity of hydroxymethylglutaryl-CoA reductase with a low apparent Km for hydroxymethylglutaryl-CoA. Mícrosomal fraction from rats fed cholestyramine exhibited a high activity with a high Km. To discover whether these changes had resulted from phosphorylation and dephosphorylation of the reductase, microsomal fraction from rats fed the supplemented diets and the standard diet were inactivated with ATP and reactivated with phosphoprotein phosphatase. Inactivation reduced the maximal activity of the reductase in each microsomal preparation and also reduced the apparent Km for hydroxymethylglutaryl-CoA. There was no difference between the preparations in the degree of inactivation produced by ATP. Treatment with phosphatase restored both the maximal activity and the apparent Km of each preparation, but never significantly increased the activity above that observed with untreated microsomal fraction. It is concluded that hydroxymethylglutaryl-CoA reductase in microsomal fraction prepared by standard procedures is almost entirely in the dephosphorylated form, and that the difference in kinetic properties in untreated microsomal fraction from rats fed the three diets cannot be explained by differences in the degree of phosphorylation of the enzyme.

scholarly journals Effect of pH on the Electrochemical Behavior of Hydrogen Peroxide in the Presence of Pseudomonas aeruginosa

2021 ◽  
Vol 9 ◽  
Author(s):  
Javier Espinoza-Vergara ◽  
Paulo Molina ◽  
Mariana Walter ◽  
Miguel Gulppi ◽  
Nelson Vejar ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Pseudomonas Aeruginosa ◽  
Enzymatic Activity ◽  
Electrochemical Behavior ◽  
Electrochemical Techniques ◽  
Stable State ◽  
Reduction Reaction ◽  
Maximum Activity ◽  
Open Circuit ◽  
Mueller Hinton

The influence of pH on the electrochemical behavior of hydrogen peroxide in the presence of Pseudomonas aeruginosa was investigated using electrochemical techniques. Cyclic and square wave voltammetry were used to monitor the enzymatic activity. A modified cobalt phthalocyanine (CoPc) carbon electrode (OPG), a known catalyst for reducing O2 to H2O2, was used to detect species resulting from the enzyme activity. The electrolyte was a sterilized aqueous medium containing Mueller-Hinton (MH) broth. The open-circuit potential (OCP) of the Pseudomonas aeruginosa culture in MH decreased rapidly with time, reaching a stable state after 4 h. Peculiarities in the E / I response were observed in voltammograms conducted in less than 4 h of exposure to the culture medium. Such particular E/I responses are due to the catalase’s enzymatic action related to the conversion of hydrogen peroxide to oxygen, confirming the authors’ previous findings related to the behavior of other catalase-positive microorganisms. The enzymatic activity exhibits maximum activity at pH 7.5, assessed by the potential at which oxygen is reduced to hydrogen peroxide. At higher or lower pHs, the oxygen reduction reaction (ORR) occurs at higher overpotentials, i.e., at more negative potentials. In addition, and to assess the influence of bacterial adhesion on the electrochemical behavior, measurements of the bacterial-substrate metal interaction were performed at different pH using atomic force microscopy.

Homogeneous oxidation of phenols in aqueous solution with hydrogen peroxide and ferric ions

1997 ◽  
Vol 36 (2-3) ◽  
pp. 151-154 ◽  
Author(s):  
H. Grigoropoulou ◽  
C. Philippopoulos
Keyword(s):  
Hydrogen Peroxide ◽  
Ferrous Sulphate ◽  
Ph Control ◽  
Chemical Oxidation ◽  
Ferric Ions ◽  
Experimental Conditions ◽  
Oxidation Rates ◽  
Homogeneous Oxidation ◽  
Oxidation Of Phenol ◽  
Ferrous Ammonium

The chemical oxidation of phenol and chlorophenols with hydrogen peroxide in the presence of soluble iron can be economically attractive at low oxidant consumption, leading then to intermediates that are more easily biodegradable. The homogeneous oxidation of phenol and chlorophenols in aqueous solutions with hydrogen peroxide is studied at oxidant : phenol ratio of about 4:1 and 16:1 (mol/mol) at various catalyst concentrations, at ambient temperature without pH control. Ferric chloride, ferric and ferrous sulphate and ferrous ammonium sulphate are used as oxidation catalysts. Ferric salts induce higher oxidation rates than ferrous ones and the nature of the anions present does not affect reaction rate. 4-Chlorophenol is found to be most resistant to oxidation and 2,4,6-Trichlorophenol is not attacked by hydrogen peroxide in the presence of ferric ions at the experimental conditions studied.

scholarly journals Differential effect of L-thyroxine on phospholipid biosynthesis in mitochondria and microsomal fraction

1980 ◽  
Vol 186 (1) ◽  
pp. 127-133 ◽  
Author(s):  
J M Pasquini ◽  
I Faryna de Raveglia ◽  
N Capitman ◽  
E F Soto
Keyword(s):  
Differential Effect ◽  
Microsomal Fraction ◽  
Liver Mitochondria ◽  
Subcellular Fractions ◽  
Control Groups ◽  
Adult Rats ◽  
And Control ◽  
Isolated Liver ◽  
Normal Controls

1. The action of L-thyroxine on the incorporation of radioactive choline or CDP-choline into phosphatidylcholine in vitro was explored in liver and brain microsomal fraction and mitochondria obtained from young adult rats. 2. In liver mitochondria isolated from animals treated with L-thyroxine (40 mg/kg body wt. during 6 days), the incorporation of both radioactive precursors into phosphatidylcholine was significantly decreased compared with normal controls, whereas in the total homogenate and in the microsomal fraction the incorporation was similar in the experimental and control groups. In subcellular fractions isolated from brain, the incorporation of precursors was similar in L-thyroxine-treated and normal animals. 3. Liver mitochondria isolated from normal animals incubated in vitro with CDP-choline, in the presence of different concentrations of L-thyroxine, showed also a marked decrease in the incorporation of label into phosphatidylcholine, whereas no significant changes were found in the total homogenate and in the microsomal fraction compared with control experiments. 4. The differential effect of L-thyroxine on the incorporation of radioactive precursors into phosphatidylcholine of isolated liver subcellular fractions gives further support to the hypothesis that liver mitochondria can independently synthesize part of their own phospholipids. 5. Possible mechanisms of the action of the hormone at the mitochondrial level are discussed.

scholarly journals The mechanism of carbon assimilation in green plants: the photolytic decomposition of carbon dioxide in vitro

1906 ◽  
Vol 78 (526) ◽  
pp. 318-327 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Peroxide ◽  
Carbon Assimilation ◽  
Enzymic Activity ◽  
Green Plants ◽  
Negative Results ◽  
Positive Side ◽  
Uranium Compounds ◽  
Photolytic Decomposition

In a previous paper* it was shown that carbon dioxide is decomposed in the green parts of plants independently of vital or enzymic activity, formaldehyde and hydrogen peroxide being produced. It follows from the analysis of the process of carbon assimilation there set out that this first step, the photolysis of carbon dioxide, should be capable of being artificially induced under laboratory conditions. It is impossible here to give a brief account of the work of previous investigators on these lines; it is sufficient to state that all experiments with chlorophyll solutions have given negative results, and as regards those with other forms of chlorophyll, such as dried powdered leaves or expressed juice, the balance of evidence favours the view that to decomposition takes place. Reference may be made to papers by Friedel and Macchiati on the positive side, and by Harroy,§ Herzog,|| and, quite recently, Bernard,¶ who obtained only negative results. Experiments with uranium compounds will be considered later.

Phosphoribosyl Pyrophosphate Degradation in Human Tissues

1974 ◽  
Vol 52 (12) ◽  
pp. 1162-1166 ◽  
Author(s):  
Irving H. Fox ◽  
Pamela J. Marchant
Keyword(s):  
Microsomal Fraction ◽  
Specific Activity ◽  
Maximum Activity ◽  
Human Tissues ◽  
Phosphoribosyl Pyrophosphate ◽  
Phosphorylated Compounds ◽  
Tissue Homogenates ◽  
Sugar Derivatives ◽  
Hydrolysis Of ◽  
Alkaline Range

Enzymatic hydrolysis of phosphoribosyl pyrophosphate (PP-ribose-P) in dialyzed human tissue homogenates had a specific activity ranging from 0.15 to 1.37 μmol mg−1 h−1. Our observations on human placenta have characterized this reaction: (1) PP-ribose-P was degraded in the absence of Mg with stoichiometric release of Pi at 37 °C; (2) the reaction occurred from pH 5 to 10.5 with the maximum activity in the alkaline range; (3) PP-ribose-P degrading activity was localized mainly in the microsomal fraction; (4) alkaline phosphatase rather than 5′-nucleotidase was responsible for the degradation of PP-ribose-P; (5) the Km for PP-ribose-P was 0.3 mM; (6) PP-ribose-P hydrolysis was altered by many phosphorylated compounds, both nucleoside and sugar derivatives, Pi, and PPi in concentrations ranging from 0.1 to 10.0 mM.

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