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.

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 Enzymatic hydrolysis of oil palm empty fruit bunch to produce reducing sugar and its kinetic Hidrolisis enzimatik tandan kosong kelapa sawit untuk menghasilkan gula pereduksi dan kinetikanya

2016 ◽  
Vol 83 (1) ◽  
Author(s):  
Vera BARLIANTI ◽  
Deliana DAHNUM ◽  
. MURYANTO ◽  
Eka TRIWAHYUNI ◽  
Yosi ARISTIAWAN ◽  
...  
Keyword(s):  
Enzymatic Hydrolysis ◽  
Oil Palm ◽  
Volume Ratio ◽  
Enzyme Concentration ◽  
Reducing Sugar ◽  
Economic Feasibility ◽  
First Order ◽  
Empty Fruit Bunches ◽  
Hydrolysis Process ◽  
Hydrolysis Of

Abstrak Sebagai salah satu Negara penghasil minyak kelapa sawit mentah (CPO), Indonesia juga menghasilkan tandan kosong kelapa sawit (TKKS) dalam jumlah besar. TKKS terdiri dari-tiga-komponen utama, yaitu selulosa, hemiselulosa, dan lignin. Pengolahan awal TKKS secara alkalindi ikuti dengan hidrolisis TKKS secara enzimatik menggunakan kombinasi enzim selulase dan β-glukosidase akan menghasilkan gula-gula yang mudah difermentasi.  Penelitian ini bertujuan untuk mempelajari pengaruh konsentrasi substrat, kon-sentrasi enzim, dan suhu selama proses hidrolisis berlangsung.  Hasil yang diperoleh menunjukkan bahwa konsentrasi gula maksimum (194,78 g/L) dicapai pada konsentrasi TKKS 20% (b/v), konsentrasi campuran enzim yang terdiri dari selulase dan β-1,4 glukosidase sebesar 3,85% (v/v), dan suhu 50oC. Perbandingan antara selulase dan β-1,4 glukosidase adalah 5:1 dengan masing-masing aktivitas enzim sebesar 144.5 FPU/mL dan 63 FPU/mL. Hasil penelitian juga menunjukkan bahwa model kinetika yang sesuai untuk proses hidrolisis TKKS secara enzimatik adalah model kinetika Shen dan Agblevor dengan reakside aktivasi enzim orde satu.  Hasil ini mendukung studi kelayakan ekonomi dalam pemanfaatan TKKS untuk produksi bioetanol.AbstractAs one of the crude palm oil producers, Indonesia also produces empty fruit bunches (EFB)in large quantities. The oil palm EFB consist of cellulose, hemicellulose and lignin. Alkaline pretreatment of EFB, followed by enzymatic hydro-lysis of cellulose using combination of cellulase and β-glucosidase enzymes produce fermentable sugars. This paper reported the effects of substrate loading, enzyme concentration, and temperature of hydrolysis process on reducing sugar production. The  maximum  sugar  concentration (194.78 g/L) was produced at 50oC using 20% (w/v) EFB and 3.85% (v/v) mixed enzymes of cellulase and β-1,4 glucosidase in volume ratio of 5:1 (v/v), with enzyme activity of 144.5 FPU/mL and 63 FPU/mL, respectively. The results also showed that the suitable kinetic model for enzymatic hydrolysis process of oil palm EFB follow Shen and Agblevor model with first order of enzyme deactivation. These results support the economic feasibility study in utilization of EFB of oil palm for bioethanol production.    

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.

scholarly journals Effect of liposomal phospholipid composition on cholesterol transfer between microsomal and liposomal vesicles

1986 ◽  
Vol 238 (3) ◽  
pp. 647-652 ◽  
Author(s):  
C Bhuvaneswaran ◽  
K A Mitropoulos
Keyword(s):  
Activation Energy ◽  
Enzyme Activity ◽  
Control System ◽  
Phospholipid Composition ◽  
Acyltransferase Activity ◽  
Phosphatidylcholine Liposomes ◽  
First Order ◽  
First Order Kinetics ◽  
Phospholipid Liposomes

Preincubation of rat liver microsomal vesicles at 37 degrees C in the presence of [3H]cholesterol/phospholipid liposomes results in a net transfer of cholesterol from liposomes to microsomal vesicles. This transfer follows first-order kinetics. For similar concentrations of the donor vesicles, rates of transfer are about 6-8 times lower with cholesterol/sphingomyelin liposomes compared with cholesterol/phosphatidylcholine liposomes. Also, transfer of cholesterol from cholesterol/sphingomyelin liposomes to microsomal vesicles reveals a larger activation energy than for the process from cholesterol/phosphatidylcholine liposomes. There is a significant correlation between the amount of liposomal cholesterol transferred to microsomal vesicles during preincubation and the increase found with acyl-CoA:cholesterol acyltransferase activity in these microsomes over their corresponding controls. If, however, liposomes made solely of phospholipids are substituted for the cholesterol/phospholipid liposomes in the preincubation system containing microsomal vesicles, then the acyl-CoA:cholesterol acyltransferase activity is decreased compared with the corresponding control system. Both sphingomyelin and phosphatidylcholine liposomes are equally effective in decreasing the enzyme activity. These results offer direct kinetic evidence for the positive correlation between cholesterol and sphingomyelin found in vivo in biological membranes.

scholarly journals The inhibition of staphylococcal β-lactamase by clavulanic acid

1979 ◽  
Vol 179 (1) ◽  
pp. 67-76 ◽  
Author(s):  
C Reading ◽  
P Hepburn
Keyword(s):  
Enzyme Activity ◽  
Clavulanic Acid ◽  
Cell Extract ◽  
Beta Lactam ◽  
Beta Lactamases ◽  
First Order ◽  
Lactam Ring ◽  
Covalent Intermediate ◽  
Hydrolysis Of ◽  
Inhibited Enzyme

Clavulanic acid inhibited both the extracellular and cell-extract beta-lactamases of the four Staphylococcus aureus strains tested. The inhibition of S. aureus Russell cell-extract enzyme appeared to be active-site-directed and proceeded in a first-order fashion consistent with the formation of a covalent intermediate. Inhibited enzyme free of excess clavulanic acid was shown to regenerate enzyme activity slowly at pH 7.0, but the rate of reactivation increased at acid pH. When the enzyme was incubated with excess clavulanic acid complete inhibition was rapidly obtained, during further incubation clavulanic acid was shown to disappear slowly and complete loss of clavulanic acid from the reaction mixture coincided with the onset of the return of enzyme activity. A reactive enamine resulting from enzymic hydrolysis of the beta-lactam ring of clavulanic acid has been proposed as a possible intermediate in the inhibitory mechanism.

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.

Angiotensin-converting enzyme preferentially hydrolyzes trans isomer of proline-containing substrate

1993 ◽  
Vol 75 (4) ◽  
pp. 1519-1524 ◽  
Author(s):  
M. P. Merker ◽  
C. A. Dawson ◽  
R. D. Bongard ◽  
D. L. Roerig ◽  
S. T. Haworth ◽  
...  
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Trans Isomer ◽  
Rate Constant ◽  
Time Course ◽  
Enzyme Concentration ◽  
Hydrolysis Rate ◽  
Converting Enzyme ◽  
Trans Form ◽  
Hydrolysis Of

An analysis of the hydrolysis kinetics of the synthetic angiotensin-converting enzyme (ACE) substrate benzoyl-phenylalanyl-alanyl-proline (BPAP) in the intact lung suggested that 12–15% of the BPAP was in a form that could not be hydrolyzed by ACE in the time course of a single pass through the lungs [C. A. Dawson et al. Am. J. Physiol. 257 (Heart Circ. Physiol. 26): H853-H865, 1989]. BPAP has been found to exist as a mixture of cis and trans isomers in a ratio of approximately 14:86 in aqueous solution at equilibrium. Thus, one possible explanation for the incomplete hydrolysis of BPAP on passage through the intact lung is that the trans form is the preferred substrate for ACE. To examine this hypothesis, we measured BPAP hydrolysis by ACE in vitro over a range of ACE concentrations and in the presence and absence of the peptidyl-prolyl cis-trans isomerase cyclophilin. In the presence of a sufficient concentration of ACE and in the absence of cyclophilin, hydrolysis of [3H]BPAP by ACE followed biexponential progress curves, consistent with the hypothesis that the rate of hydrolysis of the majority (approximately 87%) of the substrate is proportional to ACE concentration, whereas the hydrolysis rate of the remaining substrate fraction is independent of enzyme concentration. The addition of cyclophilin resulted in an increase in the ACE-independent rate constant, an effect that was reversed by the cyclophilin inhibitor cyclosporin A. These results suggest that the enzyme-independent rate constant represents the rate of cis-trans isomerization and that the enzyme-dependent rate constant represents the hydrolysis of the trans isomer.(ABSTRACT TRUNCATED AT 250 WORDS)

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 

scholarly journals A KINETIC ANALYSIS OF THE RENIN-ANGIOTONIN PRESSOR SYSTEM AND THE STANDARDIZATION OF THE ENZYMES RENIN AND ANGIOTONASE

1943 ◽  
Vol 78 (5) ◽  
pp. 367-386 ◽  
Author(s):  
Albert A. Plentl ◽  
Irvine H. Page
Keyword(s):  
Pressor Response ◽  
Accurate Method ◽  
Enzyme Concentration ◽  
Renin Substrate ◽  
First Order ◽  
First Order Kinetics ◽  
Consecutive Reactions ◽  
Slow Decline ◽  
Reaction Constant

The physicochemical background of the renal vasporessor system (renin-renin-substrate, angiotinin, angiotonase) is given. The formation and destruction of angiotonin is shown to consist of two consecutive reactions, both of which follow the laws of first order kinetics. Each reaction was studied separately and its reaction constant found to be proportional to the enzyme concentration. Hence these constants should be used to express the activity of the enzymes, renin and angiotonase. The over-all reaction of a mixture of renin and angiotonase such as occurs in kidney extracts with the α-globulin fraction of serum, viz., rapid increase followed by a slow decline in angiotonin concentration, was found experimentally to correspond closely to the theoretical values calculated for such a reaction. The curve obtained also satisfyingly explains the characteristic pressor response to the intravenous injection of renin. An accurate method for the determination of renin in the presence of angiotonase is presented.

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.

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