Time course and vectorial nature of albumin metabolism in isolated perfused rabbit PCT

1988 ◽  
Vol 255 (3) ◽  
pp. F520-F528 ◽  
Author(s):  
C. H. Park
Keyword(s):  
Time Course ◽  
Hydrolysis Product ◽  
High Capacity ◽  
Intact Protein ◽  
Renal Metabolism ◽  
First Order ◽  
First Order Kinetics ◽  
Hydrolysis Products ◽  
Renal Tubular ◽  
Hydrolysis Of

The time course and vectorial nature of renal metabolism of albumin (Alb) were studied. The tubular absorption, accumulation, and hydrolysis of Alb and the release of the hydrolysis products were determined in the isolated rabbit proximal convoluted tubule (PCT) perfused with tritiated Alb ([3H3C]Alb) at 36.4 micrograms/ml. The Alb absorption across the apical membrane was constant (99.9 +/- 4.9 x 10(-3) ng.min-1.mm-1). In contrast, the accumulation and hydrolysis of Alb in the cells increased nonlinearly with time. The bulk of the tritium that accumulated in the cells was associated with intact [3H3C]Alb. Only the final hydrolysis products were released from the cells and these first appeared in the peritubular bath 6–7 min after the start of perfusion of the tubule with [3H3C]Alb. The hydrolysis product was not detectable in the tubule lumen. The proteolytic activity correlated linearly with the protein load to the cells, characteristic of first-order kinetics and a high-capacity system. The results suggest that the renal tubular handling of proteins proceeds from the apical to the basolateral aspect of the cell. The transcellular processing of Alb is rapid and can occur in 6–7 min. The accumulation of intact protein in the cell and the first-order kinetics of hydrolysis of the absorbed protein suggest that the rate-limiting step in proximal tubular handling of proteins may include the initial hydrolysis of protein or reside in steps that precede the hydrolysis.

scholarly journals Mechanisms of thermoinactivation of endoglucanase I from Trichoderma reesei QM 9414

1992 ◽  
Vol 287 (2) ◽  
pp. 583-588 ◽  
Author(s):  
J M Dominguez ◽  
C Acebal ◽  
J Jimenez ◽  
I de la Mata ◽  
R Macarron ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Trichoderma Reesei ◽  
Time Course ◽  
Enzyme Concentration ◽  
Main Process ◽  
Peptide Bonds ◽  
First Order ◽  
First Order Kinetics ◽  
Endoglucanase I ◽  
Hydrolysis Of

The mechanism of irreversible thermoinactivation of endoglucanase I from Trichoderma reesei has been determined at 70 degrees C at the pH of maximum enzyme activity. The time-course of thermoinactivation did not follow first-order kinetics and kinetic constants of the process were dependent on enzyme concentration, suggesting that aggregation was the main process leading to irreversible inactivation. The enzyme was extremely resistant to urea, which in fact seemed to stabilize it against temperature. Disulphide exchange, deamidation and hydrolysis of peptide bonds were also responsible for the loss of enzyme activity at 70 degrees C.

ASCORBIС ACID DEGRADATION IN N, N-DIMETHYLFORMAMIDE SOLUTIONS

2020 ◽  
pp. 70-75
Author(s):  
A. V. SYROESHKIN ◽  
T. V. PLETENEVA ◽  
E. V. USPENSKAYA ◽  
I. I. SAYDINOV ◽  
O. V. LEVITSKAYA ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Optical Rotation ◽  
Hydrolysis Product ◽  
Specific Rotation ◽  
Dimethyl Formamide ◽  
Absorption Bands ◽  
Decomposition Products ◽  
First Order ◽  
First Order Kinetics ◽  
Hydrolysis Of

Objective: Investigate the mechanisms of L-ascorbic acid transforтmation and formation of coloured enamines in N, N-dimethyl-formamide solutions. Methods: An automatic polarimeter Atago POL-1/2 was used for polarimetric investigation. Electronic spectra were recorded by UV-spectrometer Cary 60 (Agilent). The statistical analysis was carried out using the OriginPro 9.1 packages. Results: The Biot’s law violation was found in below 0.1% solutions of L-ascorbic acid (AA) in N, N-dimethylformamide (DMF). During the day, the specific rotation   of 1% AA solution varied from+37 to-1.0. Gradually, the solution acquired the red colour, and its intensity depended on the AA concentration. Spectrophotometrically, it was shown that after 15 min AA was absent in the n·10-3% solutions. The decomposition followed the first-order kinetics (k1=1.83·10-2с-1). At the same time, new absorption bands appeared at 273, 390, 533 nm. Model solutions containing dimethylamine (DMA) had a similar spectrum, and the intensity of the absorption bands increased in proportion to the concentration of DMA. Conclusion: The results show that the first step in the decomposition of ascorbic acid AA in DMF follows first-order kinetics. Numerous decomposition products are optically active compounds and reverse the sign of the optical rotation of the solution. The water resulting from the decomposition of AA is involved in the hydrolysis of the solvent. The hydrolysis product, the secondary amine DMA, interacts with the carbonyl groups of the AA decomposition products to form coloured enamines. Magnesium (II) accelerates the formation of coloured products.

Acid-catalyzed Solvolysis of Isonitriles. I

1971 ◽  
Vol 49 (14) ◽  
pp. 2455-2459 ◽  
Author(s):  
Y. Y. Lim ◽  
A. R. Stein
Keyword(s):  
Formic Acid ◽  
Acid Catalysis ◽  
Hydrolysis Product ◽  
Rate Dependence ◽  
Linear Rate ◽  
First Order ◽  
Methyl Amine ◽  
Acid Catalyzed ◽  
Pseudo First Order ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of methyl isonitrile has been examined. The initial hydrolysis product is N-methylformamide which is further hydrolyzed to methyl amine and formic acid at a much slower rate. The hydrolysis to N-methylformamide is pseudo-first order in methyl isonitrile and shows a linear rate dependence on concentration of general (buffer) acid at fixed pH. The significance of general acid-catalysis in terms of the mechanism of the hydrolysis is considered and taken as evidence for carbon protonation rather than nitrogen protonation as the initiating step.

scholarly journals Fusion accessibility of endocytic compartments along the recycling and lysosomal endocytic pathways in intact cells.

1989 ◽  
Vol 109 (5) ◽  
pp. 2097-2104 ◽  
Author(s):  
N H Salzman ◽  
F R Maxfield
Keyword(s):  
Time Course ◽  
Late Endosome ◽  
Intact Cells ◽  
Degradative Pathway ◽  
First Order ◽  
First Order Kinetics ◽  
Recycling Pathway ◽  
Endocytic Vesicles ◽  
Endocytic Compartments ◽  
Endocytic Pathways

A fluorescence assay developed for the quantitation of intracellular fusion of sequentially formed endocytic compartments (Salzman, N. H., and F. R. Maxfield. 1988 J. Cell Biol. 106:1083-1091) has been used to measure the time course of endosome fusion accessibility along the recycling and degradative endocytic pathways. Transferrin (Tf) was used to label the recycling pathway, and alpha2-macroglobulin (alpha 2 M) was used to label the lysosomal degradative pathway. Along the degradative pathway, accessibility of vesicles containing alpha 2M to fusion with subsequently formed endocytic vesicles decreased with apparent first order kinetics. The t12 for the loss of fusion accessibility was approximately 8 min. The behavior of Tf is more complex. Initially the fusion accessibility of Tf decayed rapidly (t1/2 less than 3 min), but a constant level of fusion accessibility was then observed for 10 min. This suggests that Tf moves through one fusion accessible endosome rapidly and then enters a second fusion accessible compartment on the recycling pathway. At 18 degrees C, fusion of antifluorescein antibodies (AFA) containing vesicles with F-alpha 2M was observed when the interval between additions was 10 min. However, if the interval was increased to 1 h, no fusion with incoming vesicles was observed. These results identify the site of F-alpha 2M accumulation at 18 degrees C as a prelysosomal late endosome that no longer fuses with newly formed endosomes since no delivery to lysosomes is observed at this temperature.

Renal hydrolysis of absorbed protein: influence of load and lysosomal pH

1984 ◽  
Vol 247 (4) ◽  
pp. F656-F664 ◽  
Author(s):  
M. J. Camargo ◽  
B. E. Sumpio ◽  
T. Maack
Keyword(s):  
Rat Kidney ◽  
High Capacity ◽  
Lysosomal Ph ◽  
Renal Tubular Cells ◽  
Weak Bases ◽  
Uptake Rates ◽  
Cyt C ◽  
Renal Tubular ◽  
Hydrolysis Of

The kinetics of intracellular hydrolysis of administered protein and the effect of alkalinization of lysosomal pH on this process were studied in the isolated perfused rat kidney (IPK). Cytochrome c (CYT c) was used as a probe protein, and its hydrolysis was determined by measuring the efflux of radioactivity from IPK preloaded in vivo with [14CH3]CYT c and various doses of unlabeled CYT c. The nature of radioactivity absorbed by the kidney and released to the perfusate was analyzed by Sephadex chromatography. Administered CYT c is absorbed and hydrolyzed by the kidney, and the resulting amino acids are returned to the perfusate. At low uptake rates, the half time of hydrolysis of absorbed CYT c is about 20 min. The disposal of absorbed CYT c is a saturable function of its concentration in kidney with a Vmax = 0.60 mg CYT c X h-1 X g kidney-1 and an apparent Km = 0.55 mg CYT c/g kidney. To alkalinize the lysosomal pH, IPK were perfused in the presence of NH4Cl (10 mM) or chloroquine (0.1 mM). These lysosomotropic weak bases almost completely inhibit in a reversible manner the hydrolysis of absorbed CYT c. The results demonstrate that renal catabolism of absorbed protein is a saturable process of high capacity compared with the normal filtered loads of protein. The data are consistent with the view that normal lysosomal function is required for an adequate disposal of absorbed proteins in the kidney. It is postulated that abnormal deposition of protein absorption droplets within renal tubular cells may result from high absorbed loads and/or a deficient acidification of lysosomes.

URINARY EXCRETION OF INTRAVENOUSLY INJECTED 35S-SULPHATE AND 14C-UREA IN SHEEP

1975 ◽  
Vol 55 (2) ◽  
pp. 207-212 ◽  
Author(s):  
J. D. OLDHAM ◽  
G. W. MATHISON ◽  
L. P. MILLIGAN
Keyword(s):  
Urinary Excretion ◽  
Time Course ◽  
Microbial Growth ◽  
Diffusion Mechanism ◽  
Physiological Saline ◽  
Simple Diffusion ◽  
First Order ◽  
First Order Kinetics ◽  
The Difference

Sheep were injected intravenously with either 14C-urea (76.3–86.3 μc) orNa235SO4 (72.5–120.0 μc) in physiological saline. Total urinary excretion of label and, in one trial, the disappearance of label from plasma were measured for up to 106 h. Urinary recoveries were 64.9 ± 9.7% of injected 14C and 66.9 ± 12.7% of injected 35S. 35S was recovered more slowly than 14C; 99% of recovered label was collected in 36 ± 9 h after injection for 14C and in 84 ± 12 h for 35S. Disappearance of 14C from plasma approximated first-order kinetics but this was not true for 35S, which was apparently not excreted by a simple diffusion mechanism. The time course of 35S excretion from blood and into urine is discussed with reference to the potential of using the difference between intraruminally infused 35S and urinary 35S excretion as a measure of rumen microbial retention of 35S, and hence of microbial growth. It is concluded that large errors could be introduced into measurements of microbial growth by this method if that part of 35S that enters blood, but is not excreted into urine, is recycled within the animal to sites other than the rumen and retained therein.

EFFECTS OF ASCORBIC ACID AND FERUM IONS CONCENTRATION ON THE HYDROLYSIS OF GLUCOSINOLATE AND MYROSINASE ACTIVITY IN THE WATERCRESS (Nasturtium officinale sp.)

2016 ◽  
Vol 78 (8) ◽  
Author(s):  
Syamimi Mohd Zul ◽  
Noumie Surugau
Keyword(s):  
Ascorbic Acid ◽  
Enzymatic Hydrolysis ◽  
Hydrolysis Product ◽  
Carcinogenic Activity ◽  
Nasturtium Officinale ◽  
Hydrolysis Products ◽  
Low Concentrations ◽  
Health Promoting ◽  
Hydrolysis Of ◽  
Myrosinase Activity

Watercress (Nasturtium officinale sp.) from the Brassicae family contains phenethyl glucosinolates (gluconasturtiin) as the main glucosinolate (GLS). The enzymatic hydrolysis products by naturally-occuring myrosinase produced phenethyl isothicyanate (PEITC) which reported to possess anti-carcinogenic activity. Depending on several factors, its counterpart, phenethyl nitrile (PEN) can also be formed as hydrolysis product. This study investigated the effects of adding ascorbic acid and Fe2+ ions at different concentration on the hydrolysis of gluconasturtiin. Hydrolysis products were extracted using dichloromethane and analyzed semi-quantitatively by using GCMS. The results showed that PEITC increased at the low concentration of ascorbic acid (up to 0.06M). Similarly, addition of up to 0.06M Fe2+ ions increased PEITC; higher than 0.06M inhibits the formation of PEITC. Interestingly, similar trend for the production of PEN was detected. This study also investigated myrosinase activity both by exogenous and endogenous methods at different concentrations of ascorbic acid and Fe2+ ions using standard sinigrin as subsrat. Overall, the myrosinase activity was more active at the low concentrations of ascorbic acid. Also, the exogenous method is more efficient than endogenous. This study proved that the presence of reducing agents such as ascorbic acid and Fe2+ ions during the preparation of watercress as food would affect the production of the health-promoting PEITC. 

scholarly journals Acid Hydrolysis of Bis(2,2'; 6',2''–Terpyridyl) Iron(II) Complex in the Water Pools of CTAB/Hexane/Chloroform Reverse Micelles-A Kinetic Study in Confined Medium

2020 ◽  
Vol 15 (3) ◽  
pp. 853-860
Author(s):  
K. V. Nagalakshmi ◽  
P. Shyamala
Keyword(s):  
Ionic Strength ◽  
Acid Hydrolysis ◽  
Reverse Micelles ◽  
Order Rate Constant ◽  
Micellar Medium ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of acid hydrolysis of bis(2,2';6',2''–terpyridyl) iron(II) complex has been studied in CTAB/Hexane/Chloroform reverse micelles. The reaction obeys first order kinetics with respect to each of the reactants at all values of W, {W= [H2O]/[CTAB]}. In the reverse micellar medium, the reaction is much slower compared to aqueous medium due to low micropolarity of the water pools which does not facilitate a reaction between reactants of same charge. The effect of variation of W {W=[H2O]/[CTAB]} at constant [CTAB] and variation of [CTAB] at fixed W has been studied. The second order rate constant (k2) of the reaction increases as the value of W increases up to W = 8.88 and remains constant thereafter and it is independent of concentration of [CTAB] at constant W. The variation of rate of reaction with W has been explained by considering variation of micropolarity and ionic strength of water pools of reverse micelles with W. Copyright © 2020 BCREC Group. All rights reserved 

Kinetics of hydrolysis of aromatic mono- and disulfonyl chlorides

1987 ◽  
Vol 65 (9) ◽  
pp. 2263-2267 ◽  
Author(s):  
Przemyslaw Sanecki ◽  
Edward Rokaszewski
Keyword(s):  
Aqueous Acetic Acid ◽  
Polarographic Method ◽  
Acid System ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Hydrolysis ◽  
Consecutive Reactions ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

A continuous polarographic method of recording instantaneous concentrations of —SO2Cl groups in an aqueous acetic acid system containing CH3CO2Na has been elaborated. Ten model monosulfonyl chlorides underwent hydrolysis according to pseudo-first order kinetics (20% H2O, 80% v.v. CH3CO2H, 0.5 mol × dm−3 CH3CO2Na). Plots of hydrolysis for seven disulfonyl dichlorides with different number of —CH3 groups have been determined. Pseudo-first order rate constants for two consecutive reactions of hydrolysis (k1 and k2) have been computed and the influence of —SO2Cl and [Formula: see text] groups on the reactivity of the second group —SO2Cl has been discussed. The mechanism of nucleophilic substitution has also been discussed.

scholarly journals Cyclic 3', 5'-AMP relay in dictyostelium discoideum. IV. Recovery of the cAMP signaling response after adaptation to cAMP

1980 ◽  
Vol 86 (2) ◽  
pp. 545-553 ◽  
Author(s):  
M Dinauer ◽  
TL Steck ◽  
P Devreotes
Keyword(s):  
Time Course ◽  
Recovery Period ◽  
Camp Signaling ◽  
Intracellular Camp ◽  
Surface Receptors ◽  
First Order ◽  
Cellular Processes ◽  
First Order Kinetics ◽  
Rate Limiting Step ◽  
Rate Limiting

In dictyoselium discoideum, an increase in extracellular cAMP activates adenylate cyclase, leading to an increase in intracellular cAMP and the rate of cAMP secretion. Cells adapt to any constant cAMP stimulus after several minutes, but still respond to an increase in the concentration of the stimulus. We have now characterized the decay of adaptation (deadaptation) after the removal of cAMP stimuli. Levels of adaptation were established by the perfusion of [(3)H]adenosine-labeled amoebae with a defined cAMP stimulus. After a variable recovery period, the magnitude of the signaling response to a second stimulus was measured; its attenuation was taken as a measure of residual adaption to the first stimulus. The level of adaptation established by the first stimulus depended on both its magnitude and duration. Deadaptation began as soon as the first stimulus was removed. The magnitude of the response to the second stimulus increased with the recovery time in a first-order fashion, with a t(1/2)=3-4 min for stimuli of 10(-8) M to 10(-5) M cAMP. Responses to test stimuli, although reduced in magnitude, had an accelerated time-course when they closely followed a prior response that had not completely subsided. This effect is called priming; we believe it reveals a reversible, rate-limiting step that modulates the onset and termination of the signaling responses of amoebae that have not recently responded to a cAMP stimulus. We have suggested that the cAMP signaling response is controlled by two antagonistic cellular processes, excitation and adaptation. The data reported here imply that both the rate of rise in the adaptation process and the final level reached depend on the occupancy of cAMP surface receptors and that the decay of adaptation when external cAMP is removed proceeds with first-order kinetics.

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