Serine hydrolase

Serine hydrolases are one of the largest known enzyme classes comprising approximately ~200 enzymes or 1% of the genes in the human proteome. 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. First, the acyl part of the substrate is transferred to the serine, making a new ester or amide bond and releasing the other part of the substrate is released. Later, in a slower step, the bond between the serine and the acyl group is hydrolyzed by water or hydroxide ion, regenerating free enzyme. 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 and a basic residue, although variations on this mechanism exist.

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