Cyanide Binding to Carbonic Anhydrase

Abstract

From the similar 13 C chemical shifts measured for the cyanide complexes of carbonic anhydrase B enzymes and inorganic zinc cyanide complexes, it is concluded that cyanide binds in its unprotonated form directly to the zinc ion in the enzyme. The cyanide 13 C chemical shift of the enzyme · cyanide complex is pH independent indicating that neither the cyanide nor the atom to which it is bonded can undergo protolytic reactions. The 13 C spectrum of HCN is reported and the C‐H directly‐bonded coupling constant measured as 275 ± 10 Hz.