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In chemistry, the term "turnover number" has two distinct meanings.. 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]
However, as [S] gets higher, the enzyme becomes saturated with substrate and the initial rate reaches V max, the enzyme's maximum rate. The Michaelis–Menten kinetic model of a single-substrate reaction is shown on the right. There is an initial bimolecular reaction between the enzyme E and substrate S to form the enzyme–substrate complex ES.
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.
In the field of biochemistry, the specificity constant (also called kinetic efficiency or /), is a measure of how efficiently an enzyme converts substrates into products.A comparison of specificity constants can also be used as a measure of the preference of an enzyme for different substrates (i.e., substrate specificity).
The Lineweaver–Burk plot derives from a transformation of the Michaelis–Menten equation, = + in which the rate is a function of the substrate concentration and two parameters , the limiting rate, and , the Michaelis constant.
a possible mechanism of non-competitive inhibition, a kind of mixed inhibition.. Mixed inhibition is a type of enzyme inhibition in which the inhibitor may bind to the enzyme whether or not the enzyme has already bound the substrate but has a greater affinity for one state or the other. [1]
Curve of the Michaelis–Menten equation labelled in accordance with IUBMB recommendations. In biochemistry, Michaelis–Menten kinetics, named after Leonor Michaelis and Maud Menten, is the simplest case of enzyme kinetics, applied to enzyme-catalysed reactions of one substrate and one product.
Uncompetitive inhibition (which Laidler and Bunting preferred to call anti-competitive inhibition, [1] but this term has not been widely adopted) is a type of inhibition in which the apparent values of the Michaelis–Menten parameters and are decreased in the same proportion.