Serine hydrolases are one of the largest known enzyme classes comprising approximately ~200 enzymes or 1% of the genes in the human proteome.
[1] A defining characteristic of these enzymes is the presence of a particular serine at the active site, which is used for the hydrolysis of substrates.
The hydrolysis of the ester or peptide bond proceeds in two steps.
Later, in a slower step, the bond between the serine and the acyl group is hydrolyzed by water or hydroxide ion, regenerating free enzyme.
[2] Unlike other, non-catalytic, serines, the reactive serine of these hydrolases is typically activated by a proton relay involving a catalytic triad consisting of the serine, an acidic residue (e.g. aspartate or glutamate) and a basic residue (usually histidine), although variations on this mechanism exist.