European Journal of Biomedical and Pharmaceutical Sciences

REACTIVITY OF MONONUCLEAR ZINC HYDROXO COMPLEX BEARING HINDERED TRIS (PYRAZOLYL) BORATE WITH ADENINE AND THYMINE

Dr. Shalu Tyagi*

ABSTRACT

Zinc can also perform a different role in enzymes like the role it performs in carbonic anhydrase. Here the metal binds H2O and makes it acidic enough to lose a proton and form a Zn-OH group. The zinc metal serves as a nucleophile to the substrate. Since zinc has the ability to act as an electrophile or as the source of a nucleophilic group it is incorporated and used by many enzymes (10). The carbonic anhydrases (or carbonate dehydratases) form a family of enzymes that catalyze the rapid conversion of carbon dioxide and water to bicarbonate and protons, a reaction that occurs rather slowly in the absence of a catalyst. The active site of most carbonic anhydrases contains a zinc ion; they are therefore classified as metalloenzymes. The reaction rate of carbonic anhydrase is one of the fastest of all enzymes, and its rate is typically limited by the diffusion rate of its substrates. An anhydrase is defined as an enzyme that catalyzes the removal of a water molecule from a compound, and so it is this "reverse" reaction that gives carbonic anhydrase its name, because it removes a water molecule from carbonic acid. Close-up rendering of active site of human carbonic anhydrase II, showing three histidine residues and a hydroxide group coordinating the zinc ion . The present paper describes the synthesis and characterization of mononuclear zinc hydroxo complex and its reaction products with carbon dioxide, adenine and thymine.

Keywords: zinc, carbonic anhydrase, metalloenzyme, zinc-binding sites, zinc enzyme, enzyme model, catalytic hydrolysis, zinc hydroxide, carboxypeptidase, carbonic anhydrase, alcohol dehydrogenase.