Allosteric regulation of enzymatic reactions in a transparent inorganic sol-gel material

Glutamate dehydrogenase is encapsulated in a transparent porous silicate ma trix by using sol-gel techniques. The inorganic polymer is formed around th e enzyme (MW > 300,000 D). The enzyme is active in the material, catalyzes the reaction of L-glutamate to 2-oxoglutarate and follows Michaelis-Menten kinetics. The allosteric regulators ADP and GTP inhibit or activate the rea ction; at pH 6, GTP acts as a strong activator and ADP acts as an inhibitor . This system involves a complex series of interactions; the co-enzyme NAD( +) is required for catalysis, large-scale conformational changes accompany the binding of the substrate and coenzyme to the enzyme, the activators/inh ibitors must bind to the enzyme to regulate the reactions, and the substrat es and products must diffuse through the matrix to and from the binding sit e. The influence of the unique matrix on the complex enzymatic system is di scussed.