What roles do proximity and orientation play in enzymatic catalysis?

Proximity is the tendency to arrange the substrates within the active sites of the enzymes so that reactants are much closer to each other than they would be otherwise.

Orientation is the tendency of enzymes to orient substrates to maximally reactive conformation.

Proximity and orientation help lower the entropic barrier leading to the formation of the transition state so that less entropy is lost during the formation of the transition state than the free substrate would have. Enhancing the proximity and orientation of reactants causes enzymatic catalysis to occur at a faster rate. It is estimated that proper orientation in substrates can improve the reaction rate by up to approx. 100.

Hence, the reaction rate of enzymatic catalysis is accelerated by proximity and orientation.