A Computer Method for the Kinetic Analysis of Enzyme Activity

2015 ◽  
pp. 124-128
Author(s):  
P. Dolara ◽  
A. Agresti
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Computer Method

scholarly journals Uremic plasma contains factors inhibiting 1 alpha-hydroxylase activity.

1992 ◽  
Vol 3 (4) ◽  
pp. 947-952
Author(s):  
C H Hsu ◽  
S Patel
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Normal Saline ◽  
Saline Solution ◽  
Uremic Toxin ◽  
Enzyme Kinetic ◽  
Hydroxylase Activity ◽  
Normal Plasma ◽  
Guanidinosuccinic Acid ◽  
Plasma Ultrafiltrate

The effect of uremic plasma ultrafiltrate on calcitriol synthesis was investigated. Renal 1 alpha-hydroxylase activity was measured in normal rats infused for 20 h with 20 mL of normal or uremic plasma ultrafiltrate. Renal 1 alpha-hydroxylase activity was determined by the generation of calcitriol measured 5, 10, 20, and 30 min after the reaction was initiated by the addition of cold 25(OH)D3. The activity was significantly lower in rats infused with uremic plasma ultrafiltrate. Kidney homogenates preincubated for 3 h with uremic plasma ultrafiltrate also had significantly lower renal 1 alpha-hydroxylase activity than did those preincubated with normal plasma ultrafiltrate. In addition, the effect of the putative uremic toxin, guanidinosuccinic acid (GSA), on renal 1 alpha-hydroxylase activity was studied. Normal rats infused for 20 h with 20 mL of saline solution containing 1.5 mg/dL of GSA had significantly lower renal 1 alpha-hydroxylase activity than did rats infused with normal saline. The enzyme activity was also lower in kidney homogenates preincubated for 3 h with 4 mg/dL of GSA. Enzyme kinetic analysis revealed that the inhibition of renal 1 alpha-hydroxylase by GSA was noncompetitive. It was concluded that uremic plasma contains substances that directly inhibit renal 1 alpha-hydroxylase activity.

scholarly journals Na+/Ca2+ exchange in coated microvesicles

1986 ◽  
Vol 233 (3) ◽  
pp. 643-648 ◽  
Author(s):  
T Saermark ◽  
M Gratzl
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Kinetic Analysis ◽  
Transport System ◽  
Proton Transport ◽  
Ion Accumulation ◽  
Secretory Vesicles ◽  
Proton Permeability ◽  
Total Capacity

Coated microvesicles isolated from bovine neurohypophyses could be loaded with Ca2+ in two different ways, either by incubation in the presence of ATP or by imposition of an outwardly directed Na+ gradient. Na+, but not K+, was able to release Ca2+ accumulated by the coated microvesicles. These results suggest the existence of an ATP-dependent Ca2+-transport system as well as of a Na+/Ca2+ carrier in the membrane of coated microvesicles similar to that present in the membranes of secretory vesicles from the neurohypophysis. A kinetic analysis of transport indicates that the apparent Km for free Ca2+ of the ATP-dependent uptake was 0.8 microM. The average Vmax. was 2 nmol of Ca2+/5 min per mg of protein. The total capacity of microvesicles for Ca2+ uptake was 3.7 nmol/mg of protein. Both nifedipine (10 microM) and NH4Cl (50 mM) inhibited Ca2+ uptake. The ATPase activity in purified coated-microvesicles fractions from brain and neurohypophysis was characterized. Micromolar concentrations of Ca2+ in the presence of millimolar concentrations of Mg2+ did not change enzyme activity. Ionophores increasing the proton permeability across membranes activated the ATPase activity in preparations of coated microvesicles from brain as well as from the neurohypophysis. Thus the enzyme exhibits properties of a proton-transporting ATPase. This enzyme seems to be linked to the ion accumulation by coated microvesicles, although the precise coupling of the proton transport to Ca2+ and Na+ fluxes remains to be determined.

Development of an LC–MS based enzyme activity assay for MurC: application to evaluation of inhibitors and kinetic analysis

2004 ◽  
Vol 35 (4) ◽  
pp. 817-828 ◽  
Author(s):  
Gejing Deng ◽  
Rong-Fang Gu ◽  
Stephen Marmor ◽  
Stewart L. Fisher ◽  
Haris Jahic ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Activity Assay ◽  
Enzyme Activity Assay

Proteolytic Activity at Quantum Dot-Conjugates: Kinetic Analysis Reveals Enhanced Enzyme Activity and Localized Interfacial “Hopping”

Nano Letters ◽  
2012 ◽  
Vol 12 (7) ◽  
pp. 3793-3802 ◽  
Author(s):  
W. Russ Algar ◽  
Anthony Malonoski ◽  
Jeffrey R. Deschamps ◽  
Juan B. Blanco-Canosa ◽  
Kimihiro Susumu ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Quantum Dot ◽  
Kinetic Analysis ◽  
Proteolytic Activity

Framework of the kinetic analysis of O2-dependent oxidative biocatalysts for reaction intensification

2021 ◽  
Author(s):  
Alvaro Lorente-Arevalo ◽  
Miguel Ladero ◽  
Juan M. Bolivar
Keyword(s):  
Enzyme Activity ◽  
Kinetic Analysis ◽  
Oxygen Limitation ◽  
Oxygen Solubility ◽  
Low Oxygen

The application of oxygen-dependent enzymes is limited by the low oxygen solubility, a fact that hinders the full operational exploitation of the enzyme activity. This oxygen limitation also creates a...

Kinetics of Enzymatic Reactions

2007 ◽  
Author(s):  
Perry A. Frey ◽  
Adrian D. Hegeman
Keyword(s):  
Enzyme Activity ◽  
Steady State ◽  
Kinetic Analysis ◽  
Chemical Kinetics ◽  
Enzymatic Reaction ◽  
Enzymatic Reactions ◽  
Progress Curve ◽  
Steady State Kinetic ◽  
The Many ◽  
State Kinetic

At some point in characterizing an enzymatic reaction mechanism, kinetic information is required. This may range from the evaluation of the substrate specificity through comparison of Michaelis-Menten kinetic parameters Km and Vm for various substrates to the elucidation of the complete kinetic mechanism and evaluation of rate constants for all the steps. In this chapter, we outline the theory and methods of enzyme kinetics and show for a few simple cases the mechanistic information that can be derived. The steady-state kinetic analysis of enzymatic reactions nearly always entails the measurement of initial rates as a function of varying concentrations of a substrate at a fixed enzyme concentration. An initial rate best represents enzyme activity because it is the rate at time zero, before any of the many factors that can decrease enzyme activity come into play. These factors include inhibition by products, changes in pH, denaturation of the enzyme and so forth. In chemical kinetics, a large fraction of the time course for the reaction is usually measured to obtain a large number of data points to determine the kinetic order of the reaction. No problems with denaturation and product inhibition complicate such measurements. In contrast, the progress curve for an enzymatic reaction is generally sensitive to the accumulation of products, which are inhibitory and have to be taken into account. Moreover, the activity of an enzyme sometimes changes because of instability or environmental factors. However, accurate and reproducible initial rates can generally be obtained. It is possible to follow the full course of an enzymatic reaction by measuring the progress curve, as in conventional chemical kinetics. By fitting the curves to the integrated rate equations the steady-state kinetic parameters for an enzyme can be obtained from a single progress curve (Duggleby, 1995). This method has a number of advantages in principle. In practice, however, the many complications mentioned earlier, especially enzyme stability under reaction condition, have led kineticists to favor the measurement of initial rates at varying substrate concentrations in steady-state kinetic analysis.

Morphological and biochemical analyses of changes in rat hepatocytes related to wine and ethanol consumption

1984 ◽  
Vol 42 ◽  
pp. 232-233
Author(s):  
S.M. Geyer ◽  
C.L. Mendenhall ◽  
J.T. Hung ◽  
E.L. Cardell ◽  
R.L. Drake ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Malic Enzyme ◽  
Smooth Endoplasmic Reticulum ◽  
Rat Hepatocytes ◽  
Mature Male ◽  
Treatment Groups ◽  
Malic Enzyme Activity ◽  
Biochemical Analyses

Thirty-three mature male Holtzman rats were randomly placed in 3 treatment groups: Controls (C); Ethanolics (E); and Wine drinkers (W). The animals were fed synthetic diets (Lieber type) with ethanol or wine substituted isocalorically for carbohydrates in the diet of E and W groups, respectively. W received a volume of wine which provided the same gram quantity of alcohol consumed by E. The animals were sacrificed by decapitation after 6 weeks and the livers processed for quantitative triglycerides (T3), proteins, malic enzyme activity (MEA), light microscopy (LM) and electron microscopy (EM). Morphometric analysis of randomly selected LM and EM micrographs was performed to determine organellar changes in centrilobular (CV) and periportal (PV) regions of the liver. This analysis (Table 1) showed that hepatocytes from E were larger than those in C and W groups. Smooth endoplasmic reticulum decreased in E and increased in W compared to C values.

Reductive light activation of enzyme activity

2000 ◽  
Vol 110 (3) ◽  
pp. 295-295
Author(s):  
Louise Anderson ◽  
Per Gardestrom
Keyword(s):  
Enzyme Activity ◽  
Light Activation
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