STUDIES ON CORTICOSTERONE C-20 REDUCTION IN THE MOUSE

1962 ◽  
Vol 40 (1) ◽  
pp. 1797-1810 ◽  
Author(s):  
R. E. Krehbiel ◽  
A. F. Burton ◽  
Marvin Darrach
Keyword(s):  
Intravenous Injection ◽  
Mouse Liver ◽  
Enzyme Preparation ◽  
Soluble Fraction ◽  
Reductase Activity ◽  
Kinetics Of

The intravenous injection of corticosterone in the mouse was followed by liver assays for corticosterone and 20α- and 20β-dihydrocorticosterone. The 20α-epimer proved to be the more abundant product. Corticosterone 20α-reductase activity of mouse liver was shown to be associated with the dialyzed soluble fraction of the cell which served as an enzyme preparation for a study of certain properties of corticosterone 20α-reductase and the kinetics of the forward and reverse reactions.

STUDIES ON CORTICOSTERONE C-20 REDUCTION IN THE MOUSE

1962 ◽  
Vol 40 (12) ◽  
pp. 1797-1810 ◽  
Author(s):  
R. E. Krehbiel ◽  
A. F. Burton ◽  
Marvin Darrach
Keyword(s):  
Intravenous Injection ◽  
Mouse Liver ◽  
Enzyme Preparation ◽  
Soluble Fraction ◽  
Reductase Activity ◽  
Kinetics Of

The intravenous injection of corticosterone in the mouse was followed by liver assays for corticosterone and 20α- and 20β-dihydrocorticosterone. The 20α-epimer proved to be the more abundant product. Corticosterone 20α-reductase activity of mouse liver was shown to be associated with the dialyzed soluble fraction of the cell which served as an enzyme preparation for a study of certain properties of corticosterone 20α-reductase and the kinetics of the forward and reverse reactions.

THE KINETICS OF AMINO GROUP TRANSFER BY CORN RADICLE TRANSAMINASE

1957 ◽  
Vol 35 (12) ◽  
pp. 1289-1303 ◽  
Author(s):  
F. S. Cook
Keyword(s):  
Classical Theory ◽  
Spectrophotometric Method ◽  
Substrate Concentration ◽  
Enzyme Preparation ◽  
Reaction Rate ◽  
Amino Group ◽  
Group Transfer ◽  
Kinetics Of ◽  
Published Account

The kinetics of transamination are complicated by the presence of two substrates whose concentrations change appreciably during the course of the reaction. The only previously published account of the kinetics of this system deviates considerably from classical theory. Equations based on premises of Michaelis and Menten have been shown, however, to accommodate the data on reaction rate in relation to substrate concentration obtained with a corn radicle enzyme preparation by a spectrophotometric method.

scholarly journals Nitrogen degradation of the limestone-urea mixtures in the rumen of goats

2018 ◽  
Vol 43 (3) ◽  
pp. 282
Author(s):  
M. A. Harahap ◽  
L. K. Nuswantara ◽  
E. Pangestu ◽  
F. Wahyono ◽  
J. Achmadi
Keyword(s):  
Dietary Supplement ◽  
Dry Matter ◽  
Degradation Rate ◽  
Slow Release ◽  
Soluble Fraction ◽  
Degradation Kinetics ◽  
Central Java ◽  
Ruminal Degradation ◽  
Kinetics Of ◽  
Central Java Province

This experiment was aimed to study the degradation kinetics of limestone-urea mixtures in the goats rumen using the nylon bag technique. Samples of limestone were obtained from two limestone mountains, Pamotan Subdistrict of Central Java Province and Wonosari Subdistrict of Yogyakarta Province. The mixtures were created by combining urea at levels 25, 50, 75and 100%; respectively with two limestones on the basis of their Ca contents: L0U100, LP25U75, LP50U50; LP75U25, LW25U75; LW50U50; and LW75U25. The soluble fraction, potentially degradable fraction, the degradation rate of potentially degradable fraction, and effective degradation of respective dry matter (DM) and nitrogen (N) ruminal degradation kinetics were measured in each mixture. The mixture of LP75U25 had lowest effective and degradation rate of potentially degradable fraction (P<0.05) respectively for DM and N compared with those of other mixtures. In conclusion, the limestone-urea mixture of LP75U25 could be suggested as a dietary supplement of ruminal N slow release.

Paradoxical effects of piperonyl butoxide on the kinetics of mouse liver microsomal enzyme activity

1972 ◽  
Vol 21 (3) ◽  
pp. 419-427 ◽  
Author(s):  
Marvin A. Friedman ◽  
Elliott J. Greene ◽  
Robert Csillag ◽  
Samuel S. Epstein
Keyword(s):  
Enzyme Activity ◽  
Mouse Liver ◽  
Piperonyl Butoxide ◽  
Microsomal Enzyme ◽  
Paradoxical Effects ◽  
Kinetics Of

Studies on Partially Purified Pig Liver Steroid Δ4-5β-Reductase Activity

1973 ◽  
Vol 51 (12) ◽  
pp. 1661-1668 ◽  
Author(s):  
Edward J. Van Doorn ◽  
John C. Nduaguba ◽  
Albert F. Clark
Keyword(s):  
Molecular Weight ◽  
Enzyme Activity ◽  
Enzyme Preparation ◽  
Reductase Activity ◽  
Enzymatic Reaction ◽  
Ph Optimum ◽  
Pig Liver ◽  
Liver Cytosol ◽  
End Products ◽  
Tris Maleate

Some properties of partially purified steroid Δ4-5β-reductase activity of pig liver cytosol have been studied using testosterone as substrate. The enzymatic activity was stable for 72 h at 4° when stored in 0.05 M Tris–maleate buffer, pH 7.4 or 8.4; storage at pH 8 at 4° resulted in a 25% decrease in activity in 30 days. The pH optimum in Tris–maleate buffers was 6.4. Enzyme activity was completely inhibited by 0.2 mM p-chloromercuribenzenesulfonate and 0.2 mM p-chloromercuribenzoate. Enzyme activity was reduced by 20% and 45% with 1.0 mM iodoacetamide and 1.0 mM N-ethylmaleimide, respectively. The end products of the enzymatic reaction, NADP+ and 5β-dihydrotestosterone, inhibited the rate of reduction of testosterone. Testosterone Δ4-5β-reductase activity was present in protein of molecular weight 25 000–30 000, as determined by gel filtration.The enzyme preparation reduced a variety of C19 and C21 steroids. The highest activity (twice that for testosterone) was found with aldosterone as substrate.

scholarly journals Effect of a nutritional shift on the degradation of abnormal proteins in the mouse liver. Decreased degradation during rapid liver growth

1977 ◽  
Vol 164 (2) ◽  
pp. 363-369 ◽  
Author(s):  
R Amils ◽  
R D Conde ◽  
O A Scornik
Keyword(s):  
Protein Degradation ◽  
Size Distribution ◽  
Intravenous Injection ◽  
Mouse Liver ◽  
Liver Protein ◽  
Large Decrease ◽  
General Phenomenon ◽  
Liver Growth ◽  
Selective Degradation ◽  
Total Liver

1. The intravenous injection of puromycin to mice 0.5 min after administration of radioactive leucine resulted in the release of labelled ribosome-bound nascent protein chains with the next 0.5 min. 2. During the subsequent 13 min, 40% of the liver protein radioactivity disappeared. The rate of this process was already maximal 0.5 min after the injection of puromycin, with no apparent lag. 3. Evidence is presented that this phenomenon represents the selective degradation of puromycinyl-peptides: (a) the magnitude of this fraction corresponded to the calculated proportion of protein radioactivity in nascent chains at the time of the puromycin effect; (b) the size distribution of the proteins disappearing between 2 and 14 min was smaller than that of those retained at 14 min; and (c) when the injection of puromycin was delayed for 5 min, or when the leucine pulse was interrupted by the injection of cycloheximide (rather than puromycin), the fraction disappearing within 14 min was much smaller. 4. The degradation of puromycinyl-peptides was much slower in the rapidly growing livers of animals recovering from a protein depletion than in the protein-depleted controls. It is concluded that the large decrease in the overall rates of total liver protein degradation previously described during liver growth is a general phenomenon, also affecting the rate of scavenging of abnormal proteins.

scholarly journals Kinetics of creatine uptake in the perfused mouse liver: a 31P-n.m.r. study of transgenic mice expressing creatine kinase (CKBB) in the liver

1994 ◽  
Vol 303 (2) ◽  
pp. 531-538 ◽  
Author(s):  
S Masson ◽  
B Quistorff
Keyword(s):  
Creatine Kinase ◽  
Transgenic Mice ◽  
Mouse Liver ◽  
Biochemical Analysis ◽  
Perfused Liver ◽  
Creatine Uptake ◽  
Total Creatine ◽  
Kinetics Of ◽  
Dependent Mechanism

Transport of creatine in the mouse liver has been investigated in vivo and in the perfused organ. Experiments were carried out with transgenic mice expressing creatine kinase in the liver (brain isoenzyme CKBB; EC 7.2.3.2.) [Koretsky, Brosnan, Chen, Chen and Van Dyke (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 3112-3116] and in the corresponding control mice. The animals were fed a regular chow with or without the addition of 10% creatine (w/w) for 5 days. The kinetics of creatine uptake was measured in the perfused liver by 31P-n.m.r. spectroscopy and biochemical analysis following infusion of creatine at concentrations ranging over 0-15 mM and at an extracellular pH of either 7.40 or 6.40. The results suggest that creatine is actively transported by a pH-dependent mechanism obeying a saturable Michaelis-Menten type of kinetics (Km = 0.80 +/- 0.18 and 5.12 +/- 2.40 mM; Vmax. = 0.57 +/- 0.04 and 1.72 +/- 0.32 mumol.g of liver-1.min-1 at pH 7.40 and 6.40 respectively). Creatine export was evaluated in the perfused liver preloaded with creatine and the results show that less than 2.5 and 5% of the total creatine pool is exported to the perfusate during 80 min of perfusion at pH 7.40 and 6.40 respectively. Taken together, these results seem to explain the observation that creatine accumulates in the mouse liver only when blood creatine is raised by creatine feeding.

scholarly journals Measuring the CytochromecNitrite Reductase Activity—Practical Considerations on the Enzyme Assays

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Célia M. Silveira ◽  
Stéphane Besson ◽  
Isabel Moura ◽  
José J. G. Moura ◽  
M. Gabriela Almeida
Keyword(s):  
Specific Activity ◽  
Reductase Activity ◽  
Reducing Power ◽  
Desulfovibrio Desulfuricans ◽  
Electron Transfer Reaction ◽  
Nitrite Reduction ◽  
Fast Kinetics ◽  
Electrochemical Approach ◽  
Rate Limiting ◽  
Kinetics Of

The cytochromecnitrite reductase (ccNiR) fromDesulfovibrio desulfuricansATCC 27774 is able to reduce nitrite to ammonia in a six-electron transfer reaction. Although extensively characterized from the spectroscopic and structural points-of-view, some of its kinetic aspects are still under explored. In this work the kinetic behaviour of ccNiR has been evaluated in a systematic manner using two different spectrophotometric assays carried out in the presence of different redox mediators and a direct electrochemical approach. Solution assays have proved that the specific activity of ccNiR decreases with the reduction potential of the electronic carriers and ammonium is always the main product of nitrite reduction. The catalytic parameters were discussed on the basis of the mediator reducing power and also taking into account the location of their putative docking sites with ccNiR. Due to the fast kinetics of ccNiR, electron delivering from reduced electron donors is rate-limiting in all spectrophotometric assays, so the estimated kinetic constants are apparent only. Nevertheless, this limitation could be overcome by using a direct electrochemical approach which shows that the binding affinity for nitrite decreases whilst turnover increases with the reductive driving force.

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