scholarly journals The pathway of myo-inositol 1,3,4-trisphosphate dephosphorylation in liver

1987 ◽  
Vol 248 (3) ◽  
pp. 977-980 ◽  
Author(s):  
S B Shears ◽  
C J Kirk ◽  
R H Michell
Keyword(s):  
Enzyme Activity ◽  
Ionic Strength ◽  
Substrate Concentration ◽  
Initial Substrate ◽  
Liver Homogenates ◽  
Initial Substrate Concentration

We studied the dephosphorylation pathway for Ins(1,3,4)P3 (inositol 1,3,4-trisphosphate) by liver homogenates and soluble and particulate subfractions incubated in media resembling physiological ionic strength and pH. Ins(1,3,4)P3 was dephosphorylated to two InsP2 (inositol bisphosphate) isomers, one of which is Ins(3,4)P2 [Shears, Parry, Tang, Irvine, Michell & Kirk (1987) Biochem. J. 246, 139-147]. The second InsP2 is the 1,3 isomer. Ins(3,4)P2 is dephosphorylated to inositol 3-phosphate by an enzyme activity located in both soluble and particulate fractions. The phosphatase(s) that attacks Ins(1,3)P2 was largely soluble, but we have not determined which phosphate(s) is removed. When the initial substrate concentration was 1 nM, the rate of dephosphorylation of Ins(1,4)P2 greater than Ins(1,3)P2 greater than Ins(3,4)P2. None of these bisphosphates was phosphorylated when incubated with liver homogenates and 5 mM-ATP, but their rates of dephosphorylation were then decreased.

Why is the hydrolytic activity of acetylcholinesterase pH dependent? Kinetic study of acetylcholine and acetylthiocholine hydrolysis catalyzed by acetylcholinesterase from electric eel

2018 ◽  
Vol 73 (9-10) ◽  
pp. 345-351 ◽  
Author(s):  
Alena Komersová ◽  
Markéta Kovářová ◽  
Karel Komers ◽  
Václav Lochař ◽  
Alexander Čegan
Keyword(s):  
Catalytic Activity ◽  
Ionic Strength ◽  
Ph Value ◽  
Hydrolytic Activity ◽  
Initial Substrate ◽  
Electric Eel ◽  
Value Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Initial Substrate Concentration

AbstractThe dependence of the activity of acetylcholinesterase from electric eel at a pH value range of 4.8–9.8 (phosphate buffer), regarding acetylcholine and acetylthiocholine hydrolysis, was determined at 25 °C, ionic strength of 0.11 M, and initial substrate concentration of 4 mM. At a pH range of 4.8–9.8, the dependencesA(pH) form a sigmoid increasing curve with the maximum catalytic activity at a pH range 8–9.5. For acetylcholine hydrolysis, the kinetic reason for such an increase inAconsists mainly of an increase in the rate constantk2(Michaelis-Menten) model with increasing pH of the reaction mixture. For acetylthiocholine hydrolysis, the kinetic explication of the determined dependenceA(pH) is more complicated.

scholarly journals The effect of systematic error on the accuracy of Michaelis constants and maximum velocities estimated by using the integrated Michaelis–Menten equation (Short Communication)

1974 ◽  
Vol 143 (3) ◽  
pp. 779-781 ◽  
Author(s):  
Peter F. J. Newman ◽  
Gordon L. Atkins ◽  
Ian A. Nimmo
Keyword(s):  
Reaction Time ◽  
Systematic Error ◽  
Substrate Concentration ◽  
Unknown Parameter ◽  
Short Communication ◽  
Systematic Errors ◽  
Product Concentration ◽  
Initial Substrate ◽  
Michaelis Constants ◽  
Initial Substrate Concentration

Systematic errors in initial substrate concentration (s0), product concentration and reaction time give much larger errors in the Michaelis–Menten parameters unless s0 is treated as an unknown parameter. These errors are difficult to detect because the fitted curve deviates little from the data. The effect of non-enzymic reaction is also examined.

scholarly journals Evaluating the Performance of Three Chambers Microbial Salinity Cell (MSC) Subjected to Different Substrate Concentrations to Accomplish Simultaneous Organic and Salt Removal in the Wastewater

2020 ◽  
Vol 11 (1) ◽  
pp. 19-26
Author(s):  
Rustiana Yuliasni ◽  
Nur Zen ◽  
Nanik Indah Setianingsih
Keyword(s):  
Substrate Concentration ◽  
Carbon Cloth ◽  
Anode Chamber ◽  
Initial Substrate ◽  
Conductivity Increase ◽  
Maximum Current ◽  
Maximum Conductivity ◽  
Vulcan Carbon ◽  
Substrate Concentrations ◽  
Initial Substrate Concentration

This study aimed to identify the effect of substrate concentration on the performance of A Three chambers Microbial Salinity Cell (a three chambers MSC). In this study, 3 three chambers MSC was made of plexy glass with total volume of 200 ml.  Alumunium wrapped with with platinum on vulcan carbon cloth were used as electrodes,with each working area 63 cm2. The results showed that a Three chambers Microbial Salinity Cell was able to generate electricity and at the same time removed salinity. The degree of electricity deneration and salinity removal were influenced by initial substrate concentration in the anode chamber. The higher substrate concentration, the better performance of MSC. The best performance of MSC achieved when COD was 2034 mg/L, resulted in maximum  voltage of 0. 44 V, and  maximum current density of 0.29 mA/m2. With % CE was 5.4%. The maximum conductivity increase in salinity chamber was  from 11.2 µS/cm  to 1027 µS/cm (salinity 0.57% ppt).

Influence of So/Xo Ratio on Anaerobic Activity Test

1999 ◽  
Vol 40 (8) ◽  
pp. 9-15 ◽  
Author(s):  
Gloria Moreno ◽  
Arturo Cruz ◽  
Germán Buitrón
Keyword(s):  
Substrate Concentration ◽  
Reaction Rate ◽  
Biomass Concentration ◽  
Sole Source ◽  
Yield Coefficient ◽  
Initial Biomass Concentration ◽  
Activity Test ◽  
Initial Substrate ◽  
Kinetic Coefficients ◽  
Initial Substrate Concentration

The effect of the substrate/microorganism ratio during the development of anaerobic activity test was studied. The experimentation was carried out in serum bottles at 35°C. Two sets of experiments utilizing acetate and an azo dye (blue disperse 79) as the sole source of carbon were studied. It was observed that mixing has an important influence on the results. The initial substrate concentration and the initial biomass concentration had a significant effect on the reaction rate and on the biomass yield coefficient, Yobs. Different kinetic coefficients were found for the case of equal So/Xo ratio, but different initial substrate concentration.

Synthesis of (S)-Tert-Butyl 3-Hydroxybutyrate by Asymmetric Reduction of Tert-Butyl Acetoacetate with Saccharomyces cerevisiae B5

2013 ◽  
Vol 704 ◽  
pp. 12-17
Author(s):  
Zhi Min Ou ◽  
Wen Fei Feng ◽  
Li Xu
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Substrate Concentration ◽  
Asymmetric Reduction ◽  
Optical Purity ◽  
Lower Amount ◽  
High Optical Purity ◽  
Initial Substrate ◽  
Initial Ph ◽  
H 30 ◽  
Initial Substrate Concentration

S)-tert-butyl 3-hydroxybutyrate was synthesized by asymmetric reduction of tert-butyl acetoacetate with Saccharomyces cerevisiae B5 as catalyst. The enantiometric excess of (S)-tert-butyl 3-hydroxybutyrate increased with addition of more amount of substrate. High optical purity of product can be obtained when 6 g/L chloroform was used as inhibitor. The optimum reduction time, temperature, and initial pH of reaction mixture were 60 h, 30 °C, and 6.2. Addition of more biomass and lower amount of substrate helped to get high conversion. Conversion and enantiometric excess of product reached 100% when initial substrate concentration and biomass were 2.0 g/L and 140 g/L with 6 g/L chloroform as inhibitor.

scholarly journals Electrostatic effects on the kinetics of bound enzymes

1975 ◽  
Vol 145 (3) ◽  
pp. 431-435 ◽  
Author(s):  
J M Engasser ◽  
C Horvath
Keyword(s):  
Enzyme Activity ◽  
Ionic Strength ◽  
Substrate Concentration ◽  
Simple Expression ◽  
Inhibitor Concentration ◽  
Electrostatic Effects ◽  
Strength Change ◽  
Electrostatic Effect ◽  
Kinetics Of

1. The effect of the interaction between the charged matrix and substrate on the kinetic behaviour of bound enzymes was investigated theoretically. 2. Simple expression is derived for the apparent Km. 3. The apparent Km can only be used for the characterization of the electrostatic effect of the ionic strength does not vary with the substrate concentration. 4. The deviations from Michaelis-Menton kinetics are graphically illustrated for cases when the ionic strength varies with the substrate concentration. 5. The inhibition of the bound enzyme by a charged inhibitor at constant ionic strength is characterized by an apparent Ki. 6. When both the inhibitor concentration and the ionic strength change there is no apparent Ki, and the inhibition profile is graphically illustrated for this case. 7. Under certain conditions the electrostatic effects manifest thenselves in a sigmoidal dependence of the enzyme activity on the concentration of the substrate or inhibitor.

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