Usually, an enzyme molecule has only one active site, and the active site fits with one specific type of substrate. An active site contains a binding site that binds the substrate and orients it for catalysis. Residues in the binding site form hydrogen bonds, hydrophobic interactions, or temporary covalent interactions (van der Waals) with the substrate to make an enzyme-substrate complex.
The decreased volume only disrupts the equilibrium if the moles of gaseous products and moles of gaseous reactants are unequal. If there are an equal number of moles of gaseous substances on both sides of the arrow, the change in volume has an equal effect on the concentrations of reactants and of products.
If the pressure of a gas is held constant, its volume is proportional to the temperature. As the temperature increases, the atoms move faster and require more space so that they strike the walls of the container with the same net force. The volume increases. If the temperature of a gas is held constant, its pressure is inversely proportional to the volume. If the volume of a gas is decreased, then the same number of atoms moving at the same speed (because the temperature has not changed) will strike the walls of the container more often.