-If the enzyme does not alter the equilibrium constant of a reaction, how does it speed up the reaction?

-If the enzyme does not alter the equilibrium constant of a reaction, how does it speed up the reaction?-What does a graph of enzyme activity versus substrate concentration tell us about the nature of enzyme-catalyzed reactions? -Why is the induced fit model of enzyme-substrate binding a much more accurate model than the lock-and-key model? Note: Please at least 1 textbook and 1 website sources.