Studies on Human Plasma Α2-macroglobulin-enzyme Interactions
- Peter C. Harpel
- The Journal of Experimental Medicine
NH&erminal sequences were determined for human plasminogen and the S-carboxymethyl heavy (A) and light (B) chain derivatives of plasmin with a protein sequenator. The NH2-terminal 5 residues of plasminogen and the isolated S-carboxymethyl heavy (A) chain derivative isolated from plasma Fraction II12,s were determined to be Lys-ValTyr-Leu-Leu-. A second identical repeating des-lysyl sequence was found. These sequences were identical for all Fraction III2,3 plasminogen preparations and isolated isoelectric forms, pH values 6.7 and 7.8. Plasma Fraction III contains, in addition to the plasma Fraction 1112,3 isoelectric forms, other predominant isoelectric forms; the NHz-terminal 5 residues of Fraction III isolated isoelectric forms, pH v&es 6.2, 6.4, and 6.6, were determined to be Glu-Pro-Leu-Asp-Asp-. The NH&erminal 20 residues of the isolated S-carboxymethyl light (B) chain derivative of plasmin isolated from plasma Fraction 1112,3 were determined to be Val-Val-Gly-Gly-Gln-Val-Ala-His-Pro-His-Ser-TrpPro-Trp-Gln-Val-Val-Leu-Leu-Arg-. This light (B) chain sequence shows extensive homology to the NH2-terminal sequence of other serine proteases.