ureido histamine as activator of carbonic anhydrase (i) enzyme: a dft investigation

activation mechanism of human carbonic anhydrase (hca) isoform i, with ureido histamine has been investigated by using quantum mechanical calculations. the b3lyp/6-31g* method have been employed to calculate the details of electronic structure and electronic energy of active and inactive forms of carbonic anhydrase enzyme active center, isoform i (ca). ureido histamine activator of this enzyme and complex between this activator and active center of carbonic anhdrase have been investigated. the calculated results indicate that protonatable moiety of ureido histidine molecule participate in proton transfer from zinc-bound water molecule and lead to formation of the catalytically active species of ca enzyme, hydroxide coordinated to the zinc ion.