Topic
Substrate (chemistry)
About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.
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Patent•
05 Oct 1983
TL;DR: In this paper, a surface-modified electrodes which may be used in electrochemical cells for production of electrical energy comprise an enzyme immobilized on a support consisting of at least a monolayer coating of a carbonaceous pyropolymer possessing recurring units containing at least carbon and hydrogen atoms composited on a high surface area refractory inorganic oxide.
Abstract: Surface-modified electrodes which may be used in electrochemical cells for production of electrical energy comprise an enzyme immobilized on a support. The support consists of at least a monolayer coating of a carbonaceous pyropolymer possessing recurring units containing at least carbon and hydrogen atoms composited on a high surface area refractory inorganic oxide such that the carbonaceous pyropolymer monolayer coating replicates the surface area and macropore volume of the inorganic oxide. The coated support is then treated by impregnation with a water-soluble polyamine followed by contact with a solution of a molar excess of a bifunctional monomeric material to form a copolymer which provides pendant bonding sites. The copolymer is entrapped and adsorbed in the pores of the support material to provide a permanent attachment thereto. The treated support is then contacted with an excess of an enzyme to effect the conjugate attachment of the enzyme to the treated support. The immobilized enzyme will act as a working electrode in the presence of a predetermined substrate such as glucose to provide electrical energy.
172 citations
TL;DR: Primary sequence studies on the chloroplastic enzyme from C 4 plants show significant similarities to cytosolic NADP-ME in plants and animals, including a sequence motif which is indicative of the NADP + binding site.
172 citations
TL;DR: A slight modification of the Lineweaver—Burk equation, in which the form is retained but the instantaneous velocity is replaced by the negative change in substrate concentration divided by the time, allows this linear reciprocal form to be used with little error even when as much as 50% of the substrate is consumed.
172 citations
TL;DR: It is shown that this relationship accounts satisfactorily for the well-known effect of varying substrate concentration on optimum pH and velocity, and it is postulated that the conformational change is associated with a change in pK of two basic groups in the enzyme.
Abstract: 1. The effects of varying pH, ionic strength and temperature on the parameters K(m) and V(max.) for a purified alkaline phosphatase from calf intestinal mucosa with a new fluorogenic substrate, 4-methylumbelliferyl phosphate monoester disodium salt, and an ammediol-hydrochloric acid buffer system were determined. 2. It was found that, under varying conditions, a relationship exists between K(m) and V(max.) such that V(max.)=beta/(1+alpha/K(m)), where alpha and beta are constants, temperature- and ionic strength-dependent, but pH-independent. It is shown that this relationship accounts satisfactorily for the well-known effect of varying substrate concentration on optimum pH and velocity. 3. The various results are interpreted in terms of a pH-dependent conformational equilibrium between two forms of the enzyme, E(1) and E(2). Only E(1) combines with substrate, and only E(2) reacts to give inorganic phosphate. 4. To account for the pH-variation of K(m) and V(max.) in terms of this theory, it is postulated that the conformational change is associated with a change in pK of two basic groups in the enzyme.
172 citations
TL;DR: The results are discussed considering the absorption of water on the enzymes, on the supports and the solubility of water in the reaction media; all these parameters were measured separately.
Abstract: Enzymes were deposited on different porous support materials and these preparations were used to catalyze reactions in organic media. Reactions were carried out at specific water activities, achieved by equilibrating both the enzyme preparation and the substrate solution at the desired water activity before mixing them and thereby starting the reactions. The reaction rates obtained at the same water activity with different supports differed greatly, indicating a direct influence of the support on the enzyme. For horse liver alcohol dehydrogenase, Celite was the best support, and the reaction rate increased with increasing water activity. In the alpha-chymotrypsin-catalyzed alcoholysis of N-acetyl-L-phenylalanine ethyl ester with 1-butanol, high rates were again obtained with Celite, but with this support only about one third of the ethyl ester was converted to butyl ester, the rest was hydrolyzed. With the polyamide support, Accurel PA6, alcoholysis was the dominating reaction, and by using a low water activity (0.33), hydrolysis was completely suppressed while still maintaining a high alcoholysis activity. Controlled pore glass (CPG), derivatized with either hexyl or glucosyl groups, had quite different properties as enzyme supports. For horse liver alcohol dehydrogenase, glucose-CPG was a much better support than hexyl-CPG, and in the alpha-chymotrypsin-catalyzed reactions, glucose-CPG favored hydrolysis, and hexyl-CPG alcoholysis, at water activities exceeding 0.8. The results are discussed considering the absorption of water on the enzymes, on the supports and the solubility of water in the reaction media; all these parameters were measured separately.
171 citations