scholarly journals An approach to better estimation of the intial velocity of enzyme reactions

2019 ◽  
Vol 488 (2) ◽  
pp. 225-228
Author(s):  
N. M. Malygina ◽  
T. A. Petrova ◽  
A. Y. Lianguzov ◽  
A. M. Ivanov
Keyword(s):  
Initial Velocity ◽  
Kinetic Curve ◽  
Enzyme Reaction ◽  
Lag Phase ◽  
Activity Levels ◽  
Salivary Alpha Amylase ◽  
Reaction Velocity ◽  
Enzyme Reactions ◽  
Enzyme Systems ◽  
Assay Time

A new algorithm for computation of initial velocity of enzyme reaction at the time zero is proposed. This algorithm makes it possible to reduce systematic error of measurements to the minimum, to estimate reaction velocity in testing samples regardless of the enzyme activity levels and to minimize assay time. The study is illustrated by an example of salivary alpha-amylase and standard reagent kit. The algorithm should not be applied if conjugated enzyme systems are used because there is a long initial lag-phase in the kinetic curve.

Optimized Determination of γ-Glutamyltransferase by Reaction-Rate Analysis

1974 ◽  
Vol 20 (9) ◽  
pp. 1121-1124 ◽  
Author(s):  
Sidney B Rosalki ◽  
David Tarlow
Keyword(s):  
Dilute Hydrochloric Acid ◽  
Reaction Rate ◽  
Enzymatic Reaction ◽  
Enzyme Reaction ◽  
Enzyme Reactions ◽  
Rate Analysis ◽  
Acid Substrate ◽  
Incubation Buffer ◽  
Optimal Ph

Abstract We describe a method for measuring γ-glutamyltransferase (EC 2.3.2.2) activity in serum, which can be used with automated enzyme analyzers (such as the LKB 8600 Reaction Rate Analyzer) that require enzyme reactions to be initiated with substrate. The method also permits optimal determination conditions to be obtained at 37 °C. The enzymatic reaction is commenced by adding γ-glutamyl-p-nitroanilide dissolved in dilute hydrochloric acid to samples pre-incubated with tris(hydroxymethyl)aminomethane—glycylglycine buffer. The p-nitroaniline liberated is continously monitored at 37 °C at 405 nm. The pH of the pre-incubation buffer is such that the optimal pH for the enzyme reaction results from addition of the acid substrate solution.

scholarly journals H. The Kinetics of Enzyme Cascade Systems General kinetics of enzyme cascades

1969 ◽  
Vol 173 (1032) ◽  
pp. 411-420 ◽  
Keyword(s):  
Product Formation ◽  
Coagulation Cascade ◽  
Lag Phase ◽  
Open Type ◽  
Reaction Velocity ◽  
Cascade Systems ◽  
Enzyme Cascade ◽  
Enzyme Cascades ◽  
Kinetics Of ◽  
Product Relation

The theory of the kinetics of enzyme cascades is developed. Two types of cascades are recognized, one in which the products are stable ( open cascades ) and another in which the products are broken down ( damped cascades ). It is shown that it is a characteristic of a cascade that the final product appears after a certain lag phase. After this lag phase, the velocity of product formation can be very rapid. It is shown that whereas open cascades will always show a complicated time–product relation, damped cascades can under certain circumstances resemble a simple enzymic reaction. Because the relation between the over-all reaction velocity in the extrinsic coagulation cascade and the concentration of any of the proenzymes in this cascade is a hyperbolic one, it is concluded that this cascade is of the damped type rather than the open type.

Theory and practical application of coupled enzyme reactions: one and two auxiliary enzymes

1984 ◽  
Vol 62 (10) ◽  
pp. 945-955 ◽  
Author(s):  
S. P. J. Brooks ◽  
T. Espinola ◽  
C. H. Suelter
Keyword(s):  
Steady State ◽  
Enzyme System ◽  
Enzyme Reaction ◽  
Mathematical Treatment ◽  
Steady State Concentration ◽  
Practical Application ◽  
Enzyme Reactions ◽  
Time Required ◽  
The Cost ◽  
State Concentration

An extended and practical set of equations which describe coupled enzyme reactions is presented. The mathematical treatment relies on two assumptions: (a) the rate of the primary enzyme reaction is constant and (b) the reverse reactions are negligible. The treatment leads to the development of new equations which relate the time required for the concentration of a reaction intermediate to reach a defined fraction of its steady-state concentration to the kinetic parameters of the enzymes when mutarotation of one of the intermediates does not occur. The new equations reduce to those previously derived when the steady-state concentration of the intermediate is small compared with its Km value. A method for minimizing the cost of the two auxiliary enzyme system is also provided.

A New Model System for the Study of Complex Dynamical Enzyme Reactions. II. Oscillations in a Reaction-Diffusion-Convection System

1988 ◽  
Vol 43 (11) ◽  
pp. 995-1001
Author(s):  
Gerold Baier ◽  
Peter Urban ◽  
Klaus Wegmann
Keyword(s):  
Temperature Gradient ◽  
Complete System ◽  
Convective Motion ◽  
Enzyme Reaction ◽  
Reaction Diffusion ◽  
Model System ◽  
Chemical Gradient ◽  
Constant Temperature Gradient ◽  
Enzyme Reactions ◽  
Diffusion Convection

Abstract A nonlinear enzyme reaction in a chemical gradient with an artificial feed-back loop is modified by the application of a constant temperature gradient leading to laminar convective motion of the fluid at an electrode. The complete system is shown to undergo a bifurcation into a limit cycle as a function of the applied temperature gradient. The effect of other parameters on the oscillation is described. More complicated types of behavior are expected in parameter space.

Organophosphorus pesticides stress deranged kinetic values of a few midgut carbohydrases of naiad of Trithemis aurora (burm.) (Odonata: Libellulidae)

2016 ◽  
Vol 1 (02) ◽  
pp. 155-160
Author(s):  
Shekhar Chand
Keyword(s):  
Substrate Concentration ◽  
Initial Velocity ◽  
Ph Value ◽  
Organophosphorus Pesticides ◽  
Enzymatic Reaction ◽  
Organophosphorus Pesticide ◽  
Enzymatic Reactions ◽  
Reaction Velocity ◽  
Straight Line ◽  
Maximum Reaction

The 40 Hrs. treatment of last instar naiad of Trithemis aurora (Burm.) in Chlorphyriphos and Quinalphos pesticides concentrations (LC50 = 5.12 ×10-7 ppm and 7.6 × 10-8 ppm) has shown significant variations in the enzyme kinetic parameters and arrested the enzymatic activity in the midgut tissue of last instar naiad of T. aurora causing deleterious effect on various carbohydrases at standard temp. and pH value. The midgut amylase ( μ and β amylase) showed the change in the velocity of enzymatic reaction under LC50 conc. of chlorpyriphos. The data of initial velocity and substrate concentration were processed to achieve their reciprocal values. These values were plotted and a characteristic Lineweaver Burke straight line was observed from the graph and values of maximum reaction velocity (Vmax) and Michaelis Menten constants (km) were assessed. The present organophosphorus pesticide showed an inhibitory impact on midgut amylase reaction velocity. The double reciprocal plot of initial velocity and substrate concentration after exposing the enzyme under LC50 conc. of chlorphyriphos resulted in varied Vmax and Km. values. These carbohydrase on treatment with LC50 conc. of chlorphyriphos showed an inhibitory change in the reaction velocity. The 1/V and 1/S values were plotted to achieve a characteristic Lineweaver – Burke pattern of Vmax and km values obtained as 5.0 × 10-2 [M] and 2.0 under LC50 chlorphyriphos stress for α amylase. The km and Vmax values were obtained from 0.625 × 10-3 [M] to 1.25 × 10-2 [M] for various other midgut carbohydrases with Vmax value obtained from 0.28 to 5.0 under chlorpyriphos stress. The Quinalphos inhibited the enzymatic efficiencies of various carbohydrases severely and changed Km and Vmax values were found under the pesticidal stress and found as potent uncompetitive inhibitor for enzymes as values compared to the controlled enzymatic reactions by deranging the kinetic values. The Km values determined as on 1/V and 1/S basis found deranged from 1.66 × 10-3 [M] to 10 × 10-2 [M]. The Vmax values were found in a range of 0.41 to 3.3 under LC50 Quinalphos stress for midgut hydrolases. The analysis of enzymec kinetic values revealed the great inhibitory and deranged activities of various carbohydrases under both the pesticide constrain. The present toxicants were found to change the enzymatic velocity negatively. The LC50 concentrations of these toxicants were sufficient to inhibit the activity of present hydrolases as α and β amylase, α glucosidase, α galactosidase, β galactosidase, β frictosidase and α trehalase obtaining a meaningful Lineweaver – Burke line of plotted reciprocals of data of reaction velocity and substrate concentration.

Mean Lifetime and First-Passage Time of the Enzyme Species Involved in an Enzyme Reaction. Application to Unstable Enzyme Systems

2008 ◽  
Vol 70 (5) ◽  
pp. 1425-1449 ◽  
Author(s):  
E. Arribas ◽  
A. Muñoz-Lopez ◽  
M. J. Garcia-Meseguer ◽  
A. Lopez-Najera ◽  
L. Avalos ◽  
...  
Keyword(s):  
First Passage Time ◽  
Enzyme Reaction ◽  
Passage Time ◽  
First Passage ◽  
Enzyme Systems ◽  
Mean Lifetime ◽  
Enzyme Species

STEADY-STATE DEPARTURE IN ENZYME REACTIONS

1961 ◽  
Vol 39 (12) ◽  
pp. 2502-2507
Author(s):  
Hyung Kyu Shin ◽  
J. Calvin Giddings
Keyword(s):  
Steady State ◽  
Enzyme Reaction ◽  
Steady State Concentration ◽  
Simple Criterion ◽  
Enzyme Reactions ◽  
State Approximation ◽  
Steady State Approximation ◽  
State Concentration ◽  
General Method

A method is described for calculating the departure from steady-state conditions in enzyme reactions. This provides an immediate and simple criterion for the validity of the steady-state approximation. Several variations of the general method, differing in the degree of simplicity and in the treatment of initial transients, are formulated and discussed. These methods are applied to the general case of an enzyme reaction following the Michaelis–Menten mechanism. Specific applications are made using the data of Chance and Gutfreund. While in these specific cases the steady-state concentration of intermediate is reasonably accurate, the extent of reaction may easily vary from that calculated by means of the steady state.

scholarly journals Salivary Alpha-Amylase Activity Levels in Catatonic Schizophrenia Decrease after Electroconvulsive Therapy

2018 ◽  
Vol 2018 ◽  
pp. 1-5
Author(s):  
Misako Kanayama ◽  
Tsuyoshi Miyaoka ◽  
Tomoko Araki ◽  
Maiko Hayashida ◽  
Sadayuki Hashioka ◽  
...  
Keyword(s):  
Electroconvulsive Therapy ◽  
Rating Scale ◽  
Amylase Activity ◽  
Alpha Amylase ◽  
Activity Levels ◽  
Salivary Alpha Amylase ◽  
Potential Biomarker ◽  
Before And After ◽  
Catatonic Schizophrenia ◽  
Underlying Mechanisms

Background. Dysfunction of the autonomic nervous system (ANS) in schizophrenia has been detected by electrophysiological methods, but the underlying mechanisms remain unknown. Several studies have suggested that measuring salivary alpha-amylase activity levels is useful for evaluating the ANS activity and that sAA levels increase in schizophrenia and correlate with Brief Psychiatric Rating Scale (BPRS) scores. However, no study has examined the relationship between sAA activity levels and symptoms of schizophrenia with catatonic state. Methods. We present the case of a 59-year-old female with persistent catatonic schizophrenia treated by electroconvulsive therapy. We evaluated the ANS activity by measuring sAA activity levels before and after ECT, and we evaluated her symptoms using the BPRS and Bush–Francis Catatonia Rating Scale (BFCRS). Results. ECT was highly effective and BPRS and BFCRS scores substantially decreased. sAA activity levels decreased from 125 kU/l to 33 kU/l. Conclusions. sAA activity levels could be a potential biomarker of schizophrenia with catatonic state.

Sign in / Sign up

Export Citation Format

Share Document