Trypsin and ribonuclease were filtered through dextran gel (Sephadex G-100) columns in the absence and presence of their respective substrates. In the presence of their high-molecular-weight substrates the enzymes emerged earlier from the columns. This appeared to be due to the reversible formation of specific enzyme-substrate complexes. 2. The possibility of separation of an enzyme from other proteins with similar molecular weights was demonstrated with trypsin and cytochrome c in the presence of casein.
