Editing Active site (section)

===Acid/base catalysis===
In some reactions, [[protons]] and [[hydroxide]] may directly act as acid and base in term of specific acid and specific base catalysis. But more often groups in substrate and active site act as Brønsted–Lowry acid and base. This is called general acid and general base theory. The easiest way to distinguish between them is to check whether the [[reaction rate]] is determined by the concentrations of the general acid and base. If the answer is yes then the reaction is the general type. Since most enzymes have an optimum [[pH]] of 6 to 7, the amino acids in the side chain usually have a [[Acid dissociation constant|p''K''<sub>a</sub>]] of 4~10. Candidate include [[aspartate]], [[glutamate]], [[histidine]], [[cysteine]]. These acids and bases can stabilise the nucleophile or electrophile formed during the catalysis by providing positive and negative charges.<ref name=":1" />{{Rp|164–70}}