Enzymes dynamic regulation using

Abstract. TPA and RA have significant effects on glycolipid and glycoprotein biosynthetic enzymes in several cultured cell systems. This suggests that these compounds as well as other "tumor promoters" will be useful in further studies on the regulation and control of glycoconjugate metabolism (metabolic perturbants). Butyrate, TPA and RA appear to exert their effects at different points in the cell cycle. These results could mean that tumor promotion, differentiation and virus infection occur at discrete points in the cell cycle. Membrane glycoconjugates may participate in these processes in a dynamic time-dependent way. 

Peroxidases are heme-iron proteins involved in oxidative stress control. The mechanisms of this class of enzymes involve rather complex redox and electron transfer processes. These include alterations of spin state and ligands to the active-site heme as well as a novel role for Ca ions in the process as discussed by Moura and colleagues (Chapter 6). The topology and mechanism of the electron transfer process can be studied in detail using dynamic NMR data and molecular modeUng tools as illustrated by Pettigrew and co-workers (Chapter 7). The action of these types of peroxidases can be considered of crucial importance for the redox state regulation of the cell. 

A simple form of eqns (2.7-2.8), which is particularly useful in analysing the dynamics of models based on allosteric regulation with positive feedback, is obtained in the limit case where the enzyme is a dimer and the substrate binds exclusively to the R state. When incorporating parameter e into the normalization of the substrate concentration, one obtains the simplified expression (2.11) for the rate function appearing in eqns (2.7) ... 

To bring to light the various types of behaviour of which the multiply regulated enzyme system is capable, it is useful to focus on a few control parameters and to determine how their variation affects the dynamic behaviour of the model. The two parameters to be considered are the substrate injection rate, v, and the rate constant characterizing the sink of the final product P2. 

DYNAMIC INTERACTION OF LIGHT-ACTIVATED ENZYMES WITH THE THYLAKOIDS The differential binding of reduced and oxidized NADP-MDH to hydrophobic surfaces (plastic) and the specific interference of NADPH with such binding is used as a model system in order to introduce this feature as a new perspective in the situ regulation of chloroplast key enzymes. Fig. 5 illustrates this fact sho /ing that only the reduced and not the oxidized NADP-MDH attaches to the reaction vial and that the apparent loss of enzyme activity can be prevented specifically by NADPH... 

Translating a known metabolic network into a dynamic model requires rate laws for all chemical reactions. The mathematical expressions depend on the underlying enzymatic mechanism they can become quite involved and may contain a large number of p>arameters. Rate laws and enzyme parameters are still unknown for most enzymes. Convenience kinetics is used to translate a biochemical network - manually into a dynamical model with plausible biological properties. It implements enzyme saturation and regulation by activators and inhibitors, covers all possible reaction stoichiometries, and can be specified by a small number of parameters. Its mathematical form makes it especially suitable for parameter estimation and optimization. In general, the convenience kinetics applies to arbitrary reaction stoichiometries and captures biologically relevant behavior such as saturation, activation, inhibition with a small number of free parameters. It represents a simple molecular reaction mechanism in which substrates bind rapadly and in random order to the enzyme. 

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