S-adenosylhomocysteine (AdoHcy) hydrolase is an enzyme that regulates biomethylation and some other physiological processes. Recombinant AdoHcy hydrolase was overexpressed inE. coli JM109 and purified with ion exchange and gel filtration chromatographies. The effects of copper ions (Cu2+) on the activity of AdoHcy hydrolase were investigated and the results showed that Cu2+ inhibited the enzyme’s activity by a concentration and time-dependent process. The inhibition constant (Ki) and the apparent rate constant (kapp) were calculated to be (14 ±4) nmol · L−1 and (1.08 ±0.15) min−1, respectively. The existence of the natural substrate Ado could to some extent prevent Cu2+ from inactivating the enzyme, suggesting that copper ions possibly could compete with the natural substrate on enzyme’s substrate binding site. Further studies on the mechanism of inhibition are being carried out.