T H E ANTIGENICITY OF d-RIBONUCLEASE; T H E INHIBITION OF T H E ENZYME BY ITS HOMOLOGOUS IMMUNE SERUM* BY J. SMOLENS AND M. G. SEVAG

A thermostable enzyme capable of digesting d-ribose (yeast) nucleic acid was first described by W. Jones in 1920 (1). A partial purification of this enzyme with acetone was carried out by Dubos and Thompson who called the enzyme ribonuclease (2). Kunitz described the preparation and properties of a crystalline protein he isolated from beef pancreas which appeared to be the same as the ribonuclease. He provisionally called this material ribonuclease. This crystalline preparation has a molecular weight of about 15,000 (3). Enzymes have been reported to act as antigens. However, these enzymes all have had a molecular weight of at least 35,000. I t appeared of interest to determine whether an enzyme of this small molecular weight (15,000) could be antigenic. Whether the activity of the enzyme could be inhibited by its combination with specific antiserum also offered an interesting problem.