Studies on the Active Center of Human Plasmin

Tryptic digestion of the diisopropyl phosphoryl-32P-S-carboxymethyl light chain derivative of human plasmin followed by gel filtration on Sephadex G-75 and G-25 and chromatography on Dowex 50W-X2 has resulted in the isolation of three radioactive peptides. These three peptides, having 31, 33, and 34 residues, are all derived from the same segment of the plasmin molecule. Structural determinations have yielded the partial amino acid sequence, Val-Glx-(Ser-Thr, Glx)-Leu-(Gly, Ala)-His-Leu-Ala-Cys-Asn-(Thr, Gly, Gly)-Ser-Cys-Gln-Gly-Asp-Ser(diisopropyl phosphoryl-32P)-Gly-Gly-Pro-Leu-Val-Cys-Phe-Glu-Lys-Asp-Lys-Tyr.