Possible Sites of Origin of Human Plasma Ribonucleases as Evidenced by Isolation and Partial Characterization of Ribonucleases from Several Human Tissues

The ribonucleases (RNases) present in a number of human tissues, including heart, brain, lung, and kidney, were purified, partially characterized, and compared in their properties to the previously described RNases from human liver, spleen, pancreas, and serum. The enzymes appeared to fall into two major classes: liver-spleen type RNase and plasma-type RNase. These two types of enzymes were present in varying proportions in all tissues examined. The extent to which the tissues studied possibly contribute to serum RNase levels is discussed.