Purification and characterization of 5'-deoxy-5'-methylthioadenosine (MTA) phosphorylase from human liver

5'-Methylthioadenosine phosphorylase was purified 8000-fold from human liver using a combination of affinity chromatography, chromatofocusing and gel filtration. A 25% overall yield was obtained. The specific activity of the final preparation was 40 mumol of 5'-methylthioadenosine cleaved per hr per mg of protein. The enzyme had an apparent molecular weight of 55,000 daltons, as determined by gel filtration of Superose 12 and Sephadex G-150, with a subunit molecular weight of 30,000 daltons, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The substrate specificity of the purified enzyme was studied in both the direction of nucleoside cleavage and nucleoside synthesis.