There are two categories of enzymes based on kinetic features, Michaelis Menten enzymes and allosteric enzymes. Michaelis Menten enzymes will display a hyperbolic curve when initial rate is plotted against the concentration of the substrate. They also have kinetic parameters that are often studied. The Km is the subtrate concentration when the rate is half the maximum rate. This value indicates how quickly an enzyme reaches max activity, and it can be considered a measure of affinity for a particular substrate. On the other hand, Kcat is the turnover number that tells how quickly an enzyme catalyzes a reaction after it bind substrates. It is determined in saturating conditions of an enzyme, and it is particular to specific substrates. The higher the Kcat, the faster the enzyme changes substrate to product once bound. These two value are then compared to determine the specificity constant, Kcat/Km. This is the measure of an enzyme's overall catalytic efficiency. It takes into account both subtrate binding and speed of product formation, so even if an enzyme's Kcat is low, if its Km is low, its catalytic efficiency can still be decent. These kinetic parameters provide information about an enzyme's function and can be used to compare various enzymes.
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