The Carboxyl-terminal Sequence of Papain

SUMMARY Treatment of denatured papain, oxidized papain, or carboxy- methylpapain with carboxypeptidase A yields only asparagine as a carboxyl-terminal residue. The sequential action of car- boxypeptidases A and B on these derivatives yields asparagine and lysine. Only one peptide is known that is consistent with these findings, and these results place this peptide at the carboxyl- terminal end of the single peptide chain of the papain molecule. Acknowledgments-The author is indebted to Dr. Emil L. Smith for advice and encouragement in this research and to Mr. Boyd Lythgoe for performing the amino acid analyses. REFERENCES 1. SMITH, E. L., AND KIMMEL, J. R., in P. D. BOYER, H. LARDY, AND K. MYRBBCK (Editors), The enzymes, Bol. IV, Ed. 2, Academic Press, Inc., New York, 1960, p. 133. 2. FRAENKEL-CONRAT, H., HARRIS, J. I., AND LEVY, A. L., in D. GLICK (Editor), Methods of biochemical analysis, Vol. 2,