Adenosylhomocysteine hydrolase. Crystallization of the purified enzyme and its properties

Adenosylhomocysteine hydrolase (EC 3.3.1.1) from calf liver was purified to homogeneity by crystallization. The purified enzyme exhibited one single component in polyacrylamide gel electrophoresis. But by Ampholine gel electrophoresis, two isoelectric focusing variants were observed, with pI values at 5.8 and 6.0. when subjected to polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, one major subunit with a molecular weight of 60,000 was found; five other minor subunit variants were also observed, with molecular weights ranging between 50,000 and 57,000. These minor subunit variants comprised approximately 15% of the total protein applied. The molecular weight of the native enzyme was estimated to be 237,500 by gradient gel electrophoresis. The native enzyme is probably composed of four subunits, each with a molecular weight of not more than 60,000. Amino acid analyses of the purified enzyme revealed the presence of 1.2 residues of glucosamine/mol of enzyme, in addition to all of the common amino acids. The presence of enzyme-bound NAD was confirmed, probably 1 NAD molecule bound/enzyme subunit. In addition to adenosine, 3-deazaadenosine was found to be an effective substrate as well in the direction of synthesis.