Belmont University Research Symposium (BURS)


Affinity of Cadmium Versus Zinc for the Carbonic Anhydrase Active Site

Publication Date



Sciences and Mathematics, College of


Chemistry and Physics, Department of

BURS Faculty Advisor

Dr. Alison Moore Parker

Presentation Type

Oral Presentation


Cadmium is a heavy metal found in tobacco plants, nickel-cadmium batteries, and as a byproduct of metal mining. The similarities between the properties of zinc ions and cadmium ions in proteins due to their 2+ charges may cause displacement of zinc by cadmium if encountered and has been shown to do so in several transcription factors. Cadmium’s ability to replace zinc- a metal found in around 3,000 human proteins- is a cause for concern, especially due to its toxicity, long half-life in the body, and larger size.

Carbonic anhydrase is an important metalloprotein protein that relies on a central zinc(II) ion for proper folding and interaction with its substrate carbon dioxide. The focus of this research is to compare binding properties of zinc and cadmium to bovine carbonic anhydrase.

Zinc was removed from samples of bovine carbonic anhydrase using dipicolinic acid. The apoprotein was then incubated in various concentrations of zinc(II) chloride and cadmium(II) chloride solutions to quantify metal-protein binding. Filtrates devoid of protein were analyzed using atomic absorption spectroscopy (AAS) to determine cadmium and zinc concentrations. Metals found in the filtrate indicate what was not bound by the protein. Zinc was found in lesser quantities in the filtrates versus cadmium, indicating more zinc was taken up by the protein and a higher affinity for zinc; however, experiments where higher concentrations of cadmium were used had higher concentrations of zinc in the filtrate. This indicated that cadmium may be competitive for zinc binding sites in carbonic anhydrase.

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