Purification of human liver guanase and characterization of antibody against it by immunoblotting.

Guanase was purified from human liver and its specific antibody was raised in rabbits. The enzyme was purified 1200-fold from the crude liver extract; the specific activity of the purified enzyme was 91.50 units/mg. The purified enzyme gave two distinct peaks on high pressure liquid ion exchange chromatography. The materials in both peaks had a molecular weight of 100,000, and were concluded to be isozymes with different pH optima for guanine. The antiserum completely inhibited the activity of the liver enzyme. It formed a single precipitin line with the human liver extract. On immunoblotting, it bound specifically to the one band with guanase activity, but to no other bands of protein. Thus, this antiserum for human liver guanase should be suitable for use in immunohistochemical demonstration of guanase and determination of this enzyme by radioimmunoassay.