Inhibition of Cholinesterase by Dialkylcarbamates
Abstract The pI50 index and separation coefficients of chosen 3-N,N-diethylaminophenyl-N′,N′-dialkylcarbamates were determined. Index pI50 (pI50 = negative logarithm of molar concentration of inhibitor inhibiting the enzyme activity by 50%) describes the effectiveness of the inhibitor. The rate of ability of the inhibitor to pass the blood-brain barrier is usually described by the separation coefficient in a system n-octanol/water (Kow). Obtained results were compared with pI50 and Kow of Exelon®, the commercially used drug against the Alzheimer’s disease.
New Method for the Determination of the Half Inhibition Concentration (IC50) of Cholinesterase Inhibitors
A new and simple analytical method is described for the determination of the IC50 values of the inhibitors of the hydrolysis of acetylcholine (ACh) or acetylthiocholine (ATCh) by cholinesterases. The method is based on monitoring the time course of the pH value during the uninhibited and inhibited reaction. It requires only a pH meter with a suitable pH measuring cell and a small thermostated stirred batch reactor. The method has been validated for twelve different types of cholinesterase inhibitors. The determined IC50 values are comparable to those obtained by independent, more complicated, and expensive methods (Ellman´s and pH-stat).
Non-linear optimization of biochemical pathways: applications to metabolic engineering and parameter estimation
MOTIVATION
The simulation of biochemical kinetic systems is a powerful approach that can be used for: (i) checking the consistency of a postulated model with a set of experimental measurements, (ii) answering 'what if?' questions and (iii) exploring possible behaviours of a model. Here we describe a generic approach to combine numerical optimization methods with biochemical kinetic simulations, which is suitable for use in the rational design of improved metabolic pathways with industrial significance (metabolic engineering) and for solving the inverse problem of metabolic pathways, i.e. the estimation of parameters from measured variables.


RESULTS
We discuss the suitability of various optimization methods, focusing especially on their ability or otherwise to find global optima. We recommend that a suite of diverse optimization methods should be available in simulation software as no single one performs best for all problems. We describe how we have implemented such a simulation-optimization strategy in the biochemical kinetics simulator Gepasi and present examples of its application.


AVAILABILITY
The new version of Gepasi (3.20), incorporating the methodology described here, is available on the Internet at http://gepasi.dbs.aber.ac.uk/softw/Gepasi. html.


CONTACT
prm@aber.ac.uk