▁defining ▁characteristic ▁of ▁these ▁en zym es ▁is ▁the ▁presence ▁of ▁a ▁nucle oph il ic ▁ser ine ▁in ▁their ▁active ▁site , ▁which ▁is ▁used ▁for ▁the ▁hydro ly s is ▁of ▁substr ates . ▁Catal ysis ▁proceed s ▁by ▁the ▁formation ▁of ▁an ▁a cy l - enz yme ▁intermediate ▁through ▁this ▁ser ine , ▁followed ▁by ▁water / h ydro x ide - indu ced ▁sap on ification ▁of ▁the ▁intermediate ▁and ▁reg ener ation ▁of ▁the ▁en zym e . ▁Un like ▁other ▁non - catal yt ic ▁ser ines , ▁the ▁nucle oph il ic ▁ser ine ▁of ▁these ▁hyd rol ases ▁is ▁typically ▁activ ated ▁by ▁a ▁pro ton ▁relay ▁involving ▁a ▁catal yt ic ▁tri ad ▁consisting ▁of ▁the ▁ser ine , ▁an ▁acid ic ▁resid ue ▁( e . g . ▁as part ate ▁or ▁gl ut am ate ) ▁and ▁a ▁basic ▁resid ue ▁( us ually ▁hist id ine ), ▁although ▁variations ▁on ▁this ▁mechanism ▁exist . ▁ ▁Super famil ies ▁of ▁ser ine ▁hyd rol ases ▁includes : ▁▁▁ ▁Ser ine ▁prote ases , ▁including ▁try ps in , ▁ch ym ot ry ps in , ▁and ▁sub til is in ▁▁ ▁Ext rac ell ular ▁lip ases , ▁including ▁pan cre atic ▁lip ase , ▁he p atic ▁lip ase , ▁g astr ic ▁lip ase , ▁end oth el ial ▁lip ase , ▁and ▁li pop rote in ▁lip ase ▁▁ ▁Int rac ell ular ▁lip ases , ▁including ▁h