Preparation and characterization of several forms of immobilized invertase.
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Binding Sites↗
Biomedical subjects
W R Vieth
Publications and source records attributed to W R Vieth.
Kinetic modeling of the hydrolysis of sucrose by invertase.
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Glycoside Hydrolases↗
Dual role of calmodulin in excitable cells.
Consideration of the enzymatic reactions governing calcium channel phosphorylation and dephosphorylation leads one to deduce that there exist separate groups of enzymes, membrane-bound and cytoplasmic that are activated by a common mediator, calmodulin (CaM), whose time-dependent appearance (via diffusion) at both locales is controlled by both intracellular calcium levels and electrostatic interaction with the membrane. In brief, the change in the sign and extent of the electrical charge borne by the modulator in the presence of calcium (Ca) brings about the electrostatic attraction that enables the transport of [Ca-CaM] to the membrane. This translocation of Ca-CaM makes possible a sequential activation of cellular enzymes whose locations differ. The sequence, both spatial and temporal, of the activation of various cellular enzymes by Ca-CaM appears to be a control network shared in common by excitable cells containing a stimulus-response pathway mediated by second messengers.
Adenylyl Cyclases↗
Transport and kinetics in sandwiched membrane bioreactors.
A bioreactor in which living yeast cells are sandwiched between an ultrafiltration membrane and a reverse osmosis membrane was constructed, and experiments were performed for the conversion of substrate glucose to product ethanol. A set of equations that include both transport through a series of barrier layers and bioreaction rate were developed to predict the performance of the sandwich bioreactor. The above equations were solved by using numerical values for the transport parameter and the bioreaction rate constant, and the results are compared with the experimental data.
Biological Transport↗
The role of G-proteins in the regulation of pacemaking activity.
This work is concerned with modeling the key interrelated biochemical reactions involved in initiating and inhibiting pacemaking activity in the mammalian sinoatrial node. A detailed model involving G-proteins was developed to better represent the activation pathway for adenylate cyclase. Concentration profiles of an activated G-protein complex [alpha(T)C] were established as a function of the membrane bound calcium calmodulin concentration. A previously developed model used to establish temporal profiles of cAMP was improved using the G-protein effects through the [alpha(T)C] functionality. Methods were also developed to model inhibition of G-protein by acetylcholine. Analytical solutions were developed to predict acetylcholine concentration profiles as a function of diffusion parameter and duration of acetylcholine pulses. The model was used to demonstrate suppression of cAMP by acetylcholine through G-protein pathways. It provides a basis for a tool to quantify key biochemical species during stimulation and inhibition of sinoatrial node pacemaking. A stability analysis of the model equations has potential application in studying the link between the biochemical species concentrations and abnormal effects in sinoatrial node pacemaking.
Acetylcholine↗