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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TL;DR: In this article, a number of surfactants were screened for their ability to improve enzymatic hydrolysis of steam-pretreated spruce (SPS), and non-ionic surfactant was found to be the most effective.
875 citations
TL;DR: In this paper, the crystal structure of E. coli AP complexed with inorganic phosphate (Pi), which is a strong competitive inhibitor as well as a substrate for the reverse reaction, has been refined at 2.0 A resolution.
830 citations
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TL;DR: Values of the known range of spontaneous rate constants for reactions that are also susceptible to catalysis by enzymes are extended to more than 14 orders of magnitude, in contrast to previous work.
Abstract: Orotic acid is decarboxylated with a half-time (t1/2) of 78 million years in neutral aqueous solution at room temperature, as indicated by reactions in quartz tubes at elevated temperatures. Spontaneous hydrolysis of phosphodiester bonds, such as those present in the backbone of DNA, proceeds even more slowly at high temperatures, but the heat of activation is less positive, so that dimethyl phosphate is hydrolyzed with a t1/2 of 130,000 years in neutral solution at room temperature. These values extend the known range of spontaneous rate constants for reactions that are also susceptible to catalysis by enzymes to more than 14 orders of magnitude. Values of the second-order rate constant kcat/Km for the corresponding enzyme reactions are confined to a range of only 600-fold, in contrast. Orotidine 59-phosphate decarboxylase, an extremely proficient enzyme, enhances the rate of reaction by a factor of 10(17) and is estimated to bind the altered substrate in the transition state with a dissociation constant of less than 5 x 10(-24) M.
813 citations
TL;DR: The data gave no evidence for the presence of an acyl intermediate; if such an intermediate exists it must be very rapidly hydrolyzed, and the pH dependence curves appear to reflect the catalytic center activity.
812 citations
TL;DR: Thermodynamic comparisons between spontaneous and enzyme-catalyzed reactions, coupled with structural information, suggest that in addition to electrostatic and H-bonding interactions, the liberation of water molecules from an enzyme's active site into bulk solvent sometimes plays a prominent role in determining the relative binding affinities of the altered substrate in the ground state and transition state.
Abstract: The fastest known reactions include reactions catalyzed by enzymes, but the rate enhancements that enzymes produce had not been fully appreciated until recently. In the absence of enzymes, these same reactions are among the slowest that have ever been measured, some with half-times approaching the age of the Earth. This difference provides a measure of the proficiencies of enzymes as catalysts and their relative susceptibilities to inhibition by transition-state analogue inhibitors. Thermodynamic comparisons between spontaneous and enzyme-catalyzed reactions, coupled with structural information, suggest that in addition to electrostatic and H-bonding interactions, the liberation of water molecules from an enzyme's active site into bulk solvent sometimes plays a prominent role in determining the relative binding affinities of the altered substrate in the ground state and transition state. These comparisons also indicate a high level of synergism in the action of binding determinants of both the substrate a...
802 citations