pH

The optimum pH of an enzyme is the pH value at which it catalyses its reaction at the maximum possible rate. Changing the surrounding pH alters the ionisation state of the amino acid side chains that make up the enzyme, including those that form its active site; this changes the enzyme's overall shape and can prevent the substrate from binding correctly, reducing catalytic activity. If the enzyme is exposed to extremes of pH - either far too acidic or far too alkaline for it - the disruption to its structure becomes severe enough that the enzyme denatures altogether and permanently loses its activity. Different enzymes are adapted to very different optimum pH values depending on where in the body they work: for example, the digestive enzyme pepsin, which works in the strongly acid …