Ping–pong Mechanisms
Enzymes with a ping-pong mechanism can exist in two states, E and a chemically modified form of the enzyme E*; this
modified enzyme is known as an intermediate. In such mechanisms, substrate A binds, changes the enzyme to E* by, for
example, transferring a chemical group to the active site, and is then released. Only after the first substrate is released can
substrate B bind and react with the modified enzyme, regenerating the unmodified E form. When a set of v by [S] curves
(fixed A, varying B) from an enzyme with a ping–pong mechanism are plotted in a Lineweaver–Burk plot, a set of parallel
lines will be produced. This is called a secondary plot.
Enzymes with ping–pong mechanisms include some oxidoreductases such as thioredoxin peroxidase, transferases such as
acylneuraminate cytidylyltransferase and serine proteases such as trypsin and chymotrypsin.
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