The velocity-substrate curve below characterizes an allosteric enzyme system. The curve demonstrates that:

Ans. B. A modifier binding to the allosteric site can also affect the catalytic sitea. When a modifier binds at the allosteric site, it affects the active site by altering Vmax and Km.b. The substrate binds to the active, or catalytic, site, where it is modified. Binding of both substrate and modifier is, of course, concentration-dependent.c. The velocity of an allosteric enzyme reaction depends on the concentration of both the substrate and the modifier.