Catalyzes the hydrolysis of S-adenosyl-L-homocysteine to form adenosine and homocysteine (PubMed:10933798). 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. Identified by mass spectrometry in melanosome fractions from stage I to stage IV. The disease is caused by variants affecting the gene represented in this entry. Belongs to the adenosylhomocysteinase family.