Kinetics and Mechanism of Dissociation of Zinc Ion from Carbonic Anhydrase

✍ Scribed by Alice Y. Romans; Mary E. Graichen; C.H. Lochmuller; Robert W. Henkens

• Publisher: Elsevier Science
• Year: 1978
• Weight: 461 KB
• Volume: 9
• Category: Article
• ISSN: 0006-3061
• DOI: 10.1016/s0006-3061(78)80007-6

✦ Synopsis

The kinetics of dissociation of Zn 2+ from the metalloenzyme carbonic anhydrase was measured over a range of pH, temperature, and acetate concentration. The rate of dissociation is extremely slow at neutral pH (tl/2 ~ 3 years, 4°C), but increases in almost direct proportion to the hydrogen ion concentration and is enhanced in the presence of 1,10-phenanthroline or acetate. The thermodynamic stability of the zinc-apoenzyme complex was determined over a range of pH from rate data on binding and dissociation (stability constants 109-1011 M -I, 25°C). The great stability of the complex and slow exchange of the apoenzyme ligand is attributed, at least in part, to the rigidity of the multidentate protein ligand.