Purification of a ribonuclease inhibitor from Novikoff hepatoma supernatant fraction.

A comparison between the levels of ribonuclease inhibitor in normal rat liver and Novikoff hepatoma 105,000 X g supernatant fractions is reported. Novikoff hepatoma con tained 61% less inhibitor per g of tissue or 39% less per mg protein than did normal rat liver. A rapid and simple method that had been developed for the purification of rat liver ribonuclease inhibitor was applied to Novikoff hepatoma 105,000 X g supernatant fraction. The purification procedure led to a 121-fold increase in specific activity, with a yield of 49%. The molecular weight and inhibition curve of purified inhibitor were also determined and were found to be similar to those of normal rat liver ribonuclease inhibitor.