ON THE ROLE OF TRYPTOPHAN IN THE ACTIVITY OF ADENOSINE-DEAMINASE

The activity of purified adenosine deaminase isolated from the gray an d white matter of bovine brain was inhibited by chemical modification of tryptophan residues with N-bromosuccinimide and photooxidation in t he presence of trichloroethanol. Only two of six modified residues wer e essential for activity of the enzyme. A preliminary kinetic study sh owed that these essential. tryptophan residues are adjacent to the sub strate-binding site of the enzyme.