Catalyzes the hydrolysis of S-adenosyl-L-homocysteine to form adenosine and homocysteine (PubMed:10933798). Binds copper ions (By similarity). {ECO:0000250|UniProtKB:P50247, ECO:0000269|PubMed:10933798}. This is the function of ENSG00000101444 (AHCY, adenosylhomocysteinase).