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Enzyme catalysis is the increase in the rate of a process by an "enzyme", a biological molecule. Most enzymes are proteins, and most such processes are chemical reactions. Within the enzyme, generally catalysis occurs at a localized site, called the active site.
The reaction catalysed by an enzyme uses exactly the same reactants and produces exactly the same products as the uncatalysed reaction. Like other catalysts, enzymes do not alter the position of equilibrium between substrates and products. [1] However, unlike uncatalysed chemical reactions, enzyme-catalysed reactions display saturation kinetics.
Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. The study of how fast an enzyme can transform a substrate into a product is called enzyme kinetics. The rate of reaction of many chemical reactions shows a linear response as function of the concentration of substrate molecules.
A decade before Michaelis and Menten, Victor Henri found that enzyme reactions could be explained by assuming a binding interaction between the enzyme and the substrate. [11] His work was taken up by Michaelis and Menten, who investigated the kinetics of invertase, an enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose. [12]
Enzymes (/ ˈ ɛ n z aɪ m z /) are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates , and the enzyme converts the substrates into different molecules known as products .
Although general-acid catalysis for breakdown of the First and Second tetrahedral intermediate may occur by the path shown in the diagram, evidence supporting such a mechanism with chymotrypsin [25] has been controverted. [26] The second stage of catalysis is the resolution of the acyl-enzyme intermediate by the attack of a second substrate.
In enzymology, the turnover number (k cat) is defined as the limiting number of chemical conversions of substrate molecules per second that a single active site will execute for a given enzyme concentration [E T] for enzymes with two or more active sites. [1] For enzymes with a single active site, k cat is referred to as the catalytic constant. [2]
Kinetically perfect enzymes have a specificity constant, k cat /K m, on the order of 10 8 to 10 9 M −1 s −1.The rate of the enzyme-catalysed reaction is limited by diffusion and so the enzyme 'processes' the substrate well before it encounters another molecule.