Circular dichroism changes in adenosine deaminase upon substrate analog binding

Circular dichroism studies with adenosine deaminase from calf intestinal mucosa are described. Addition of purine riboside, a competitive inhibitor of the enzyme, does not cause modification of mean residue ellipticity in the CD spectra in the region between 250 and 185 nm, but increases markedly the ellipticity in the 300-250 nm region. The data are consistent with the view that a conformational change involving aromatic amino acid residues occurs upon binding of purine riboside to adenosine binding site of adenosine deaminase.