Lysozyme turnover number

The term represents the kinetic efficiency of the enzyme. Table 14.4 lists turnover numbers for some representative enzymes. Catalase has the highest turnover number known each molecule of this enzyme can degrade 40 million molecules of HgOg in one second At the other end of the scale, lysozyme requires 2 seconds to cleave a glycosidic bond in its glycan substrate. 

The maximum rate is directly related to the rate at which the enzyme processes or permits conversion of the reactant molecule(s). The number of moles of reactants processed per mole of enzyme per second is called the turnover number. Turnover numbers vary widely. Some are high, such as for the scavenging of harmful free radicals by catalase, with a turnover number of about 40 million. Others are small, such as the hydrolysis of bacterial cell walls by the enzyme lysozyme, with a turnover number of about one half. 

Turnover numbers for some representative enzymes are listed in table 7.2. The enormous value of 4 x 107 mole-cules/s achieved by catalase is among the highest known the low value for lysozyme is at the other end of the spectrum. As is the case with Km, the relationship of kcal to individual rate constants, such as k2 and k3, depends on the details of the reaction mechanism. 

The fin ax of an enzyme is a measure of how fast the reaction it catalyzes can proceed once the enzyme-substrate complex is formed. This is related to the turnover numberthe number of substrate molecules converted into product per active site at very high substrate concentration. Turnover numbers vary from very high (e.g., 600,000 sec-1 for carbonic anhydrase) to relatively slow (e.g., 0.5 sec-1 for lysozyme). Another name for turnover number is cat, which is related to Em ax and the total enzyme concentration, [E] (measured as number of active sites per unit volume of solution), as follows Em ax = Acat x [E],... 

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