ISSN:
1432-1424
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Biologie
,
Chemie und Pharmazie
Notizen:
Summary Two different artificial membrane systems bearing two built-in sequential enzymes are studied and compared in this communication. The first is a nonstructured membrane bearing two mixed enzymes: β-galactosidase and glucose-oxidase. Its use enables a mathematical model to be formulated describing the heterogeneous phase kinetics of a bienzymatic system. The second is a multi-layer membrane system in which the structural dissymmetry involves a spatial orientation of the reacting metabolites, resulting in active glucose transport. The latter system consists of two active leaflets, the first phosphorylating glucose (hexokinase+ATP), the second dephosphorylating glucose-6 phosphate (phosphatase). On either side of this system, a perm-selective proteic layer allows the passage of glucose but not of glucose-6 phosphate. When positioned between two compartments containing glucose, such a membrane accumulates glucose on its phosphatase side, while degrading ATP. The accumulation of glucose as a function of the initial concentration shows the classical saturation of the transport system. Fructose competes with glucose transport. The chemical balance of these two reactions has the appearance of hydrolysis of ATP. Vectorial catalysis is a result of the dissymmetry in distribution of active sites and can be explained by an oscillatory concentration profile of glucose inside the membrane. The bienzymatic mechanism, a model of which is given here, is valid for any thickness of active layers and applicable to a system where both active sides are part of the same molecule as soon as it forms a uniformly oriented monolayer throughout the membrane structure.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF01868108
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