S-Adenosyl-L-homocysteine (AdoHcy) hydrolase has been shown to have (5'/6') hydrolytic activity with vinyl (5') or homovinyl (6') halides derived from adenosine (Ado). This hydrolytic activity is independent of its 3'-oxidative activity. The vinyl (or homovinyl) halides are converted into 5'(or 6')-carboxaldehydes by the hydrolytic activity of the enzyme, and inactivation occurs via the oxidative activity. Amide and ester derivatives of Ado-5'-carboxylic acid were prepared to further probe the hydrolytic capability of AdoHcy hydrolase. The oxidative activity (but not the hydrolytic activity) is involved in the mechanism of inhibition of the enzyme by the ester and amide derivatives of Ado-5'-carboxylic acid, in contrast to the inactivation of this enzyme by adenosine-derived vinyl or homovinyl halide analogues during which both activities are manifested.