Kinetic and crystallographic studies of the role of tyrosine 7 in the active site of human carbonic anhydrase II

► Replacing Tyr7 in the active site of human carbonic anhydrase II enhanced proton transfer in catalysis. ► Replacement of Try7 caused reduced thermal stability. ► Replacement of Tyr7 with Ile caused a conformational change at the amino terminus. ► Results demonstrate a role for Tyr7 in folding and stability for carbonic anhydrases in the α class.