Catalyzes the hydrolysis of S-adenosyl-L-homocysteine to form adenosine and homocysteine (PubMed:11927587). Binds copper ions (By similarity). H2O + S-adenosyl-L-homocysteine = adenosine + L-homocysteine Binds 1 NAD(+) per subunit. Amino-acid biosynthesis; L-homocysteine biosynthesis; L-homocysteine from S-adenosyl-L-homocysteine: step 1/1. Homotetramer. Belongs to the adenosylhomocysteinase family.