Mechanisms of enzyme-mediated reactions.

(A) Formation of an enzyme-substrate complex. (B1) Enzyme specificity depends on a proper fit of the active site and substrate. (B2) A reactant that is close in shape to the active site may compete with the normal substrate and decrease the rate of the reaction. (B3) Some compounds may interact with the active site and lock into place, thus removing all activity. (B4) Changes in the active site can affect the ability of the enzyme to interact with its normal substrate. (C) An excess of substrate slows the rate of reaction. (D) An increase in the enzyme concentration will increase the rate of reaction since the substrate does not have to wait for a free active site.